List of publications from different databases
And below is a selected set of publications:
2024
2024
-
Review of top quark mass measurements in CMS
CMS Collaboration
arXiv:2403.01313, Mar 2024
The top quark mass is one of the most intriguing parameters of the standard model (SM). Its value indicates a Yukawa coupling close to unity, and the resulting strong ties to the Higgs physics make the top quark mass a crucial ingredient for understanding essential aspects of the electroweak sector of the SM. While it is such an important parameter of the SM, its measurement and interpretation in terms of the Lagrangian parameter are challenging. The CMS Collaboration has performed multiple measurements of the top quark mass, addressing these challenges from different angles: highly precise ‘direct’ measurements, using the top quark decay products, as well as ‘indirect’ measurements aiming at accurate interpretations in terms of the Lagrangian parameter. Recent mass measurements using Lorentz-boosted top quarks are particularly promising, opening a new avenue of measurements based on top quark decay products contained in a single particle jet, with superior prospects for accurate theoretical interpretations. Moreover, dedicated studies of the dominant uncertainties in the modelling of the signal processes have been performed. This review offers the first comprehensive overview of these measurements performed by the CMS Collaboration using the data collected at centre-of-mass energies of 7, 8, and 13 TeV.
-
Top Quark at the New Physics Frontier
E. Yazgan, and P. Silva
Mar 2024
The hunt for top quarks began back in the 1970s after the proposal of the sixquark model by Kobayashi and Maskawa, and it was discovered in 1995 at the Fermilab Tevatron. It was experimentally established by five different experiments in different production modes and a variety of collision energies. At the CERN Large Hadron Collider (LHC), top quark–antiquark pairs are routinely produced at a rate of about six per minute, enabling experiments to make detailed measurements of the properties of top quarks. The analysis of the data collected at the Tevatron and the LHC experiments has revealed, so far, good agreement with the standard model (SM) predictions. The top quark is the most massive elementary particle identified to date: not only does it have a privileged Yukawa coupling to the Higgs boson, but its mass is also significantly higher than that of the Higgs boson. Owing to its large mass, the top quark decays before hadronization, making the study of “bare” quark properties possible in experimental settings. Therefore, top quark physics simultaneously pushes the frontiers of quantum chromodynamics, electroweak, and flavor physics. The aim of this reprint is to provide a comprehensive review of the status and prospects of top quark physics at the LHC and possible future colliders. We have included articles that especially emphasize where the present understanding is incomplete and suggest new directions for research in this area.
-
Top Quark at the New Physics Frontier - Editorial
Efe Yazgan, and Pedro Silva
Universe 10 (2024) 124, Mar 2024
This Special Issue of Universe is devoted to the most massive fundamental elementary particle known, the top quark [...]
-
Search for new Higgs bosons via same-sign top quark pair production in association with a jet in proton-proton collisions at \sqrts = 13 TeV
CMS Collaboration
Phys. Lett. B. 850 (2024) 138478, Feb 2024
A search is presented for new Higgs bosons in proton-proton (pp) collision events in which a same-sign top quark pair is produced in association with a jet, via the pp→tH∕A→ttc and pp→tH∕A→ttu processes. Here, H and A represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on ppcollision data collected at a center-of-mass energy of 13TeVwith the CMS detector at the LHC, corresponding to an integrated luminosity of 138fb−1. Final states with a same-sign lepton pair in association with jets and missing transverse momentum are considered. New Higgs bosons in the 200–1000GeV mass range and new Yukawa couplings between 0.1 and 1.0 are targeted in the search, for scenarios in which either H or A appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed. Exclusion limits are derived in the context of the g2HDM.
2023
2023
-
Search for new Higgs bosons through same-sign top quark pair production in association with a jet in proton-proton collisions at 13 TeV
CMS Collaboration
CMS-PAS-TOP-22-010, Feb 2023
A search is presented for new Higgs bosons in proton-proton collision events in which a same-sign top quark pair is produced in association with a jet, via the cg→tH/A→ttc and cg→tH/A→ttu processes. Here H and A represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on proton-proton collision data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb−1. Final states with a same-sign lepton pair in association with a charm or up quark are considered. New Higgs bosons in the 200−1000 GeV mass range are targeted in the search, for scenarios in which either H or A appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed, and exclusion limits are derived in the context of the g2HDM. Depending on the g2HDM signal assumptions, the mass of a new Higgs boson below 1 TeV and corresponding new Yukawa couplings between 0.4 and 1 are excluded at the 95% confidence level.
-
CMS PYTHIA 8 colour reconnection tunes based on underlying-event data
CMS Collaboration
Euro. Phys. J. C 83 (2023) 587, May 2023
New sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the pythia 8 event generator, are obtained based on the default CMS pythia 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies sqrt(s) = 7 and 13 TeV, and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair (ttbar) events. The new tunes are also used to estimate the uncertainty related to colour reconnection modelling in the top quark mass measurement using the decay products of ttbar events in the semileptonic channel at 13 TeV.
2022
2022
-
TF07 Snowmass Report: Theory of Collider Phenomena
F. Maltoni, and others
Phys. Lett. B., arXiv:2210.02591, FERMILAB-FN-1203-QIS, Oct 2022
Theoretical research has long played an essential role in interpreting data from high-energy particle colliders and motivating new accelerators to advance the energy and precision frontiers. Collider phenomenology is an essential interface between theoretical models and experimental observations, since theoretical studies inspire experimental analyses while experimental results sharpen theoretical ideas. This report – from the Snowmass 2021 Theory Frontier topical group for Collider Phenomenology (TF07) – showcases the dynamism, engagement, and motivations of collider phenomenologists by exposing selected exciting new directions and establishing key connections between cutting-edge theoretical advances and current and future experimental opportunities. By investing in collider phenomenology, the high-energy physics community can help ensure that theoretical advances are translated into concrete tools that enable and enhance current and future experiments, and in turn, experimental results feed into a more complete theoretical understanding and motivate new questions and explorations.
-
Event Generators for High-Energy Physics Experiments
J. M. Campbell, and others
arXiv:2203.11110, Mar 2022
We provide an overview of the status of Monte-Carlo event generators for high-energy particle physics. Guided by the experimental needs and requirements, we highlight areas of active development, and opportunities for future improvements. Particular emphasis is given to physics models and algorithms that are employed across a variety of experiments. These common themes in event generator development lead to a more comprehensive understanding of physics at the highest energies and intensities, and allow models to be tested against a wealth of data that have been accumulated over the past decades. A cohesive approach to event generator development will allow these models to be further improved and systematic uncertainties to be reduced, directly contributing to future experimental success. Event generators are part of a much larger ecosystem of computational tools. They typically involve a number of unknown model parameters that must be tuned to experimental data, while maintaining the integrity of the underlying physics models. Making both these data, and the analyses with which they have been obtained accessible to future users is an essential aspect of open science and data preservation. It ensures the consistency of physics models across a variety of experiments.
-
Distances of galactic radio pulsars; first quadrant: -2 < l < 90 and -2 < b < 2
Pinar Kutukcu, Askin Ankay, Efe Yazgan, and 1 more author
Monthly Notices of the Royal Astronomical Society 511 (2022) 4669, Apr 2022
Distance versus dispersion measure relations are constructed for Galactic radio pulsars in small solid angle intervals. The calculations are based on some basic criteria as well as using the independent distance measurements of well examined pulsars for the first Galactic quadrant including Galactic central directions. Values of average free electron density for these regions are derived from the fits to distance versus dispersion measure relations and checked for consistency and smoothness. The effects of plasma in the Galactic arms and within the central parts of the Galactic bulge region are also compared and discussed. Our adopted distances for the radio pulsars are compared with the ones given in some other models. Some basic results on distributions of the radio pulsars and the plasma are presented.
-
Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map
Ivan Alonso, and others
Euro. Phys. J. Quantum Techno. 9 (2022) 30, Jan 2022
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.
2021
2021
-
Modelling the Data at the LHC
Efe Yazgan
arXiv:2110.02599, CMS CR-2021/166; PoS (PANIC2021) 410, Oct 2021
Measurements at hadron colliders rely on large scale quantum chromodynamics (QCD) Monte Carlo (MC) production for interpretation of the data. MC simulations allow testing Standard Model (SM) with more accurate and precise calculations to understand perturbative QCD as well as electroweak effects, and extrapolations of the irreducible backgrounds to signal phase-space regions for new physics searches or for the measurements of rare SM processes. In the MC codes, there are many pieces, approximations, and parameters and settings to compare to the data and tune. Precise experimental measurements at the LHC require similar level of precision in theoretical calculations. Cross sections measured at the LHC both by ATLAS and CMS experiments cover more than 14 orders of magnitude. So far, SM cross section predictions are found to be in very good agreement with the data. These cross sections are measured at different pp collision energies and compared to prediction up to next-to-next-to-leading order (NNLO) for many processes, and recently up to N3LO for some of them. In this note, a few measurements relevant to data modelling are discussed.
-
HL-LHC Computing Review Stage-2, Common Software Projects: Event Generators
Efe Yazgan, and others
arXiv/2109.14938 [hep-ph, hep-ex, physics.comp-ph]; FERMILAB-PUB-21-526-OCIO-SCD-T, Sep 2021
This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group (WG), as an input to the second phase of the LHCC review of High-Luminosity LHC (HL-LHC) computing, which is due to take place in November 2021. It complements previous documents prepared by the WG in the context of the first phase of the LHCC review in 2020, including in particular the WG paper on the specific challenges in Monte Carlo event generator software for HL-LHC, which has since been updated and published, and which we are also submitting to the November 2021 review as an integral part of our contribution.
-
Challenges in Monte Carlo Event Generator Software for High-Luminosity LHC
Comput. Softw. Big Sci. 5 (2021) 12, Sep 2021
We review the main software and computing challenges for the Monte Carlo physics event generators used by the LHC experiments, in view of the High-Luminosity LHC (HL-LHC) physics programme. This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group as an input to the LHCC review of HL-LHC computing, which has started in May 2020.
2020
2020
-
AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space
Yousef Abou El-Neaj, and others
Euro. Phys. J. Quant. Techno. 7 (2020) 6, Sep 2020
We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. KCL-PH-TH/2019-65, CERN-TH-2019-126
-
Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements
Albert M Sirunyan, and others
Eur. Phys. J. C 80 (2020) 4, Sep 2020
New sets of CMS underlying-event parameters (“tunes”) are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell–Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.
2019
2019
-
A Roadmap for HEP Software and Computing R&D for the 2020s
Johannes Albrecht, and others
Comput. Softw. Big Sci. 3 (2019) 7, Sep 2019
Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.
-
Study of the underlying event in top quark pair production in pp collisions at 13 TeV
Albert M. Sirunyan, and others
Eur. Phys. J. C 79 (2019) 123, Sep 2019
Measurements of normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event in top quark and antiquark pair production are presented. The measurements are performed in proton-proton collisions at a center-of-mass energy of 13 TeV, and are based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 fb−1. Events containing one electron, one muon, and two jets from the hadronization and fragmentation of b quarks are used. These measurements characterize, for the first time, properties of the underlying event in top quark pair production and show no deviation from the universality hypothesis at energy scales typically above twice the top quark mass.
-
Quantum Chromodynamics Monte Carlo TuningStudies in CMS
Efe Yazgan
PoS DIS (2019) 080, Sep 2019
Recent QCD Monte Carlo tuning studies done in the CMS Collaboration are presented. Jet kine- matics, jet substructure, and underlying event measurements in top quark pair events are dis- cussed. New CMS PYTHIA 8 event tunes are presented, exploiting Monte Carlo configurations with consistent parton distribution functions and strong coupling parameter values in the matrix element and the parton shower, at leading order (LO), next-to-leading order (NLO) and next-to- next-to-leading order (NNLO). Predictions from PYTHIA 8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets. The tunes are validated with a range of different measurements and matrix element-parton shower merged configurations.
2018
2018
-
Top Quark Modeling and Generators in CMS
Efe Yazgan
arXiv:1801.05025, CMS-CR-2017-404, Jan 2018
Recent top quark event modeling studies done using LHC proton-proton collision data collected with the CMS detector at centre of mass energies of 8 and 13 TeV and state-of-the-art theoretical predictions are summarized. A new factorized approach for parton shower uncertainties is presented. A top quark specific PYTHIA8 CMS tune, along with tunes using new color reconnection models, is discussed. The possibility of having a consistent choice of parton distribution function in the matrix element and the parton shower is demonstrated with tunes constructed with leading, next-to-leading, and next-to-next-to-leading order versions of NNPDF3.1 set compared to minimum bias and underlying event data.
-
Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report
J. R. Andersen, and others
arXiv:1803.07977, FERMILAB-CONF-18-122-CD-T, UWTHPH-2018-5, Mar 2018
This Report summarizes the proceedings of the 2017 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) theoretical uncertainties and dataset dependence of parton distribution functions, (III) new developments in jet substructure techniques, (IV) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (V) phenomenological studies essential for comparing LHC data from Run II with theoretical predictions and projections for future measurements, and (VI) new developments in Monte Carlo event generators.
2017
2017
-
Top Quark Properties Measurements in CMS
Efe Yazgan
Nuovo Cim. C 39 (2017) 341, Mar 2017
Recent top quark properties measurements made with the CMS detector at the LHC are presented. The measurements summarized include spin correlation of top quark pairs, asymmetries, top quark mass, and the underlying event in top quark pair events. The results are compared to the standard model predictions and new physics models.
-
Top quark modelling and generators in CMS
Efe Yazgan
Proceedings of Science EPS-HEP (2017) 474, Mar 2017
Recent top quark event modelling studies done using CMS proton-proton data collected at a centre of mass energies of 8 and 13 TeV and state-of-the-art theoretical predictions accurate to next-to-leading order QCD interfaced with PYTHIA and HERWIG event generators are summarised. The particle-level top quark (pseudo-top), underlying event measurement in ttbar events and parton shower tuning using ttbar events are discussed.
2016
2016
-
On the Galactic Distributions of Radio Pulsars and Plasma Density
A. Ankay, E. Yazgan, and P. Kutukcu
Serb. Astro. J. 193 (2016) 1, Mar 2016
A brief review of distance measurement methods for some astro- nomical sources is presented. Galactic plasma density distribution as related to the distribution of radio pulsars is discussed and a method for constructing relations between dispersion measure and distance for Galactic radio pulsars in small solid angle intervals is described. Dispersion measure – distance relations for radio pulsars based on this approach in the Galactic longitude and latitude intervals of Delta(l) = 0 +/- 2 and Delta(b) = 0 +/- 2 are displayed and comparisons are made with the predictions of the two commonly used models.
-
Measurement of Spin Correlations in ttbar Production using the Matrix Element Method in the Muon+Jets Final State in pp Collisions at sqrt(s) = 8 TeV
CMS Collaboration
Phys. Lett. B 758 (2016) 321, Mar 2016
Spin correlations and polarization in the top quark–antiquark system are measured using dilepton final states produced in pp collisions at the LHC at √s=7 TeV. The data correspond to an integrated luminosity of 5.0 fb−1 collected with the CMS detector. The measurements are performed using events with two oppositely charged leptons (electrons or muons), a significant imbalance in transverse momentum, and two or more jets, where at least one of the jets is identified as originating from a b quark. The spin correlations and polarization are measured through asymmetries in angular distributions of the two selected leptons, unfolded to the parton level. All measurements are found to be in agreement with predictions of the standard model.
-
Measurement of Top Quark Properties in Single Top-Quark Production at CMS
Efe Yazgan
Nucl. Part. Phys. Proc. 273-275 (2016) 2142, Mar 2016
Single top-quark t-channel production is exploited for studies of top quark properties. The analyses include the measurement of the CKM matrix element, |Vtb|, search for anomalous couplings of the top quark using a Bayesian neural network analysis, measurement of single top-quark polarization which directly confirms the V-A nature of the tWb production vertex, and the measurement of W-helicity fractions in the phase space sampled by a selection optimized for t-channel single top-quark production, orthogonal to the ttbar final states used in traditional measurements of these properties. All measurements are found to be consistent with the standard model predictions.
2015
2015
-
Top Quark Measurements in CMS
Efe Yazgan
Nucl. Part. Phys. Proc. 258-259 (2015) 117, Mar 2015
2014
2014
-
Measurements of ttbar Spin Correlations and Top-Quark Polarization Using Dilepton Final States in pp Collisions at sqrt(s) = 7 TeV
Phys. Rev. Lett. 112 (2014) 182001, Mar 2014
Spin correlations and polarization in the top quark–antiquark system are measured using dilepton final states produced in pp collisions at the LHC at √s=7 TeV. The data correspond to an integrated luminosity of 5.0 fb−1 collected with the CMS detector. The measurements are performed using events with two oppositely charged leptons (electrons or muons), a significant imbalance in transverse momentum, and two or more jets, where at least one of the jets is identified as originating from a b quark. The spin correlations and polarization are measured through asymmetries in angular distributions of the two selected leptons, unfolded to the parton level. All measurements are found to be in agreement with predictions of the standard model.
-
Flavor changing neutral currents in top quark production and decay
Efe Yazgan
arXiv:1312.5435, CMS-CR-2013-398, CMS CR-2013/398, Mar 2014
Top quark flavor changing neutral current (FCNC) interactions are highly suppressed in the Standard Model. Therefore, any large signal of FCNCs will indicate the existence of new interactions. In this paper, searches for FCNC interactions in top quark production and decay at the Tevatron and LHC are presented. FCNC searches in t->qZ and t->Hq decays, and in top quark production in pp->t+j, pp->t+Z are summarized. Effect of top quark FCNCs on single top quark cross-section, and the searches for same-sign top quark pair production through FCNCs are also described. None of the searches yielded positive results and exclusion limits on branching rations, coupling strengths and cross-sections are obtained. Future prospects of FCNC searches are also briefly discussed.
2013
2013
-
Forward-Backward Asymmetry of Drell-Yan Lepton Pairs in pp Collisions at sqrt(s) = 7 TeV
CMS Collaboration
Phys. Lett. B 718 (2013) 752, Mar 2013
A measurement of the forward-backward asymmetry (A[FB]) of Drell-Yan lepton pairs in pp collisions at sqrt(s) = 7 TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5 inverse femtobarns. The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are also presented. The A[FB] measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions.
-
Measurements of Top Quark Properties at the LHC
Efe Yazgan
arXiv:1304.3324, CMS-CR-2013-077, CMS-CR-2013-077; CERN-CMS-CR-2013-077, Mar 2013
Recent measurements of top quark properties at the LHC from ATLAS and CMS experiments are presented. The presented results include top quark mass, dependence of top mass measurements on event kinematics, top anti-top mass difference, bottom quark content in top quark decays, W boson polarization and anomalous couplings, search for CP violation in single top events, vector boson production associated with top-antitop pairs and top polarization.
-
Measurements of the top-quark properties at CMS
Efe Yazgan
arXiv:1308.3338, CMS-CR-2013-077, CMS-CR-2013-077; CERN-CMS-CR-2013-077, Aug 2013
2012
2012
-
Some test results of an anti-Cherenkov photomultiplier tube
N. Akchurin, J. Damgov, S. W. Lee, and 1 more author
Nucl. Instrum. Meth. A 695 (2012) 143, Aug 2012
We report on the beam test results of a photomultiplier tube (PMT) specially designed to suppress the signal due to Cherenkov light emitted by window glass when impacted by relativistic charged particles. This signal becomes a concern when it is comparable to the true PMT signal, especially in the case of calorimeters, where the response is at the level of a few photoelectrons per GeV. This design allows for placement of these PMTs behind the calorimeter without concern for hot spots from the Cherenkov background.
2011
2011
-
Measurement of the weak mixing angle with the Drell-Yan process in proton-proton collisions at the LHC
CMS Collaboration
Phys. Rev. D 84 (2011) 112002, Aug 2011
A multivariate likelihood method to measure electroweak couplings with the Drell–Yan process at the LHC is presented. The process is described by the dilepton rapidity, invariant mass, and decay angle distributions. The decay angle ambiguity due to the unknown assignment of the scattered constituent quark and antiquark to the two protons in a collision is resolved statistically using correlations between the observables. The method is applied to a sample of dimuon events from proton-proton collisions at √s=7 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 1.1 fb−1. From the dominant u¯u, d¯d→γ∗/Z→μ−μ+ process, the effective weak mixing angle parameter is measured to be sin2θeff=0.2287\pm0.0020 (stat.)\pm0.0025 (syst.). This result is consistent with measurements from other processes, as expected within the standard model.
2010
2010
-
Identification and Filtering of Uncharacteristic Noise in the CMS Hadron Calorimeter
CMS Collaboration
J. Instr. 5 (2010) T03014, Aug 2010
Commissioning studies of the CMS hadron calorimeter have identified sporadic uncharacteristic noise and a small number of malfunctioning calorimeter channels. Algorithms have been developed to identify and address these problems in the data. The methods have been tested on cosmic ray muon data, calorimeter noise data, and single beam data collected with CMS in 2008. The noise rejection algorithms can be applied to LHC collision data at the trigger level or in the offline analysis. The application of the algorithms at the trigger level is shown to remove 90% of noise events with fake missing transverse energy above 100 GeV, which is sufficient for the CMS physics trigger operation.
-
Performance of the CMS Hadron Calorimeter with Cosmic Ray Muons and LHC Beam Data
CMS Collaboration
J. Instr. 5 (2010) T03012, Aug 2010
The CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked.
2009
2009
-
The CMS barrel calorimeter response to particle beams from 2-GeV/c to 350-GeV/c
ECAL/HCAL USCMS Collaboration
Eur. Phys. J. C 60 (2009) 359, Aug 2009
[Erratum: Eur.Phys.J.C 61, 353–356 (2009)]
The response of the CMS barrel calorimeter (electromagnetic plus hadronic) to hadrons, electrons and muons over a wide momentum range from 2 to 350 GeV/c has been measured. To our knowledge, this is the widest range of momenta in which any calorimeter system has been studied. These tests, carried out at the H2 beam-line at CERN, provide a wealth of information, especially at low energies. The analysis of the differences in calorimeter response to charged pions, kaons, protons and antiprotons and a detailed discussion of the underlying phenomena are presented. We also show techniques that apply corrections to the signals from the considerably different electromagnetic (EB) and hadronic (HB) barrel calorimeters in reconstructing the energies of hadrons. Above 5 GeV/c, these corrections improve the energy resolution of the combined system where the stochastic term equals 84.7\pm1.6% and the constant term is 7.4\pm0.8%. The corrected mean response remains constant within 1.3% rms.
2008
2008
-
Search for a standard model Higgs boson in CMS via vector boson fusion in the H to WW to lnulnu channel
E. Yazgan, J. Damgov, N. Akchurin, and 6 more authors
Eur. Phys. J. C 53 (2008) 329, Aug 2008
We present the potential for discovering the standard model Higgs boson produced via the vector-boson fusion mechanism. We considered the decay of Higgs bosons to the W+W- final state, with both W-bosons subsequently decaying leptonically. The main background is tt̄ produced in association with one or more jets. This study is based on a full simulation of the CMS detector. The result is that a signal of 5σ significance can be obtained with an integrated luminosity of 12–72 fb-1 for Higgs boson masses in the range 130<mH< 200 GeV. In addition, the major background can be measured directly to 7% from the data with an integrated luminosity of 30 fb-1. We also suggest a method to determine the Higgs mass using template transverse mass distributions.
2007
2007
-
Neutron Stars, Supernovae and Supernova Remnants
Oktay H. Guseinov, Efe Yazgan, and Askin Ankay
Aug 2007
In the 1930s scientists discovered that the Universe is expanding and that it is quite old. The observation of hydrogen lines in the spectrum of the Sun helped Niels Bohr construct his atomic model in 1912, and understand the optical spectra of atoms. This era marked the transition of astronomy into astrophysics. With the rapid technological progress, scientists were able to study the universe in different ways that enabled them to observe what could not be observed using ordinary telescopes. Technology enabled scientists to see the universe in x-rays, gamma rays, radio waves and even look inside stars with neutrinos. One of the most important results of these developments, the observation of very high energy particles from cosmic distances, led to a complete new branch of physics, namely high energy physics, and provided a valuable tool to understand the very high energy processes going on in the universe such as in shock fronts of supernova remnants. In the 1960s very important discoveries in astrophysics like the microwave background radiation from the Big Bang, quasars, X-ray binaries, pulsars and cosmic X-ray sources followed. A significant interest in astrophysics prevailed and many physicists began to work on these new objects and processes. Among many great physicists, Yakov B. Zeldovich and Igor D. Novikov are worth noting especially because of their efforts which accelerated the theoretical and phenomenological researches in all of these branches of astrophysics. Astrophysics began to push the boundaries of physics and our world view. Astrophysical results were rewarded with Nobel prizes. Three of these Nobel prizes (1974, 1993, 2002) were given to works on neutron stars. This book is mainly devoted to neutron stars and to objects related to them.
-
Core Collapse Supernovae
E. Yazgan
Nova Science Publishers, Aug 2007
-
Search for a Standard Model Higgs boson in CMS via vector boson fusion in the H->WW->lvlv channel and optimization of energy reconstruction in CMS using test beam 2006 data
Efe Yazgan
PhD Thesis, FERMILAB-THESIS-2007-13, CERN-THESIS-2007-052, Aug 2007
One of the goals of the LHC is to test the existence of the Higgs boson. This thesis presents a study of the potential to discover the Standard Model Higgs boson in the vector boson fusion (VBF) channel for the Higgs mass range 120- 200 GeV/c2. The decay of Higgs bosons into the WW final state with both W -bosons decaying leptonically is considered. The main backgrounds are tt + j and W +W −jj. This study, based on a full simulation of the CMS detector at the LHC, shows that a 5σ discovery can be done with an integrated luminosity of 12 − 72 fb−1 for 130 − 200 GeV/c2 Higgs bosons. Due to the uncertainties in the backgrounds, it is important to measure the backgrounds from data. This study shows that the major background can be measured directly to 7% with 30 fb−1. After discovering the Higgs boson, it will be crucial to probe its physical properties. A method to measure the Higgs boson mass using transverse mass template distributions is investigated in the VBF channel. iv The performance of the combined CMS electromagnetic and hadronic calorime- ters (EB+HB) was measured at the H2 test beam at the CERN SPS during 2006 with various particles in a large momentum range, 1-350 GeV/c. Another major contribution of this thesis is developing the method to optimize the energy recon- struction for the combined EB+HB system with which the corrected responses become 100% with 6% fl and the stochastic resolution is improved from 111% to 94%.
2006
2006
-
Pulsar Distances and the Electron Distribution in the Galaxy
Efe Yazgan, Oktay H. Guseinov, and Sevinç Tagieva
Nova Science Publishers, Jan 2006
2005
2005
-
Analysis of Fall-Back Disk and Magnetar Models of Anomalous X-Ray Pulsars and Soft Gamma Repeaters
Efe Yazgan, Oktay H. Guseinov, Aşkin Ankay, and 2 more authors
Nova Science Publishers, Jan 2005
-
Early Phases of Different Types of Isolated Neutron Star
Aşkin Ankay, Serkan Şahin, Gökçe Karanfil, and 1 more author
Int. J. Mod. Phys. D 14 (2005) 1075, Jan 2005
Two Galactic isolated strong X-ray pulsars seem to be in the densest environments compared to other types of Galactic pulsar. X-ray pulsar J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma repeaters if its average braking index is 1.8-2.0. X-ray pulsar J1811-1925 must have a very large average braking index ( 11) if this pulsar was formed by SN 386AD. This X-ray pulsar can be in an early phase of the evolution of the radio pulsars located in the region P 50-150 ms and Pdot 10-14-10-16 ss-1 of the P-Pdot diagram. X-ray/radio pulsar J0540-69 seems to be evolving in the direction to the dim isolated thermal neutron star region on the P-Ṗ diagram. Possible progenitors of different types of neutron star are also discussed.
-
Stability of Carbon Nanotori under Heat Treatment: Molecular‐Dynamics Simulations
E. Taşcı, E. Yazgan, O. B. Malcıoglu, and 1 more author
Fullerenes, Nanotubes and Carbon Nanostructures 13 (2005) 147, Jan 2005
The structural stability of carbon nanotori have been investigated by performing molecular‐dynamics simulations. The systems considered are C170, C250, C360, C520 and C750 tori, which have been constructed using a recently developed algorithm based on the idea of Fonseca et al. Calculations, have been realized by using an empirical many‐body potential energy function for carbon. It has been found that all the nanotori considered are stable under heat treatment.
-
Structural and Electronic Properties of (CnLi)+ Cluster Ions
Efe Yazgan, and Sakir Erkoc
Int. J. of Mod. Phys. C 16 (2005) 271, Jan 2005
The structural and electronic properties of (CnLi)+ cluster ions with n =1–6 and n =20 have been investigated by performing density functional theory calculations at B3LYP level. The vibrational frequencies of the clusters are also calculated.
-
Can Science Explain Everything? Anything? (Translation by Y. Uzunefe-Yazgan, E. Yazgan)
S. Weinberg
TUBITAK Bilim ve Teknik Dergisi, Mar 2005
2004
2004
-
AN ALGORITHM TO GENERATE TOROIDAL AND HELICAL CAGE STRUCTURES USING PENTAGONS, HEXAGONS AND HEPTAGONS
EFE YAZGAN, EMRE TAŞCI, and ŞAKIR ERKOÇ
Int. J. of Mod. Phys. C 15 (2004) 267, Mar 2004
An algorithm to generate toroidal or helical cage structures has been developed. Any toroidal or helical structure can be generated following four stages. In the first stage a Fonseca type unit cell and its symmetrical counterpart is formed which represents one-fifth of a toroid. In the second stage one-fifth fragment of the torus is fully obtained by applying geometry optimization to the structure obtained in the first stage. In the third stage the torus fragment obtained in the second stage is reproduced five times and connected to each other to generate either toroidal or helical structure. In the last stage a final optimization process is reapplied to get the complete structure desired.
-
Electronic properties of carbon nanotoroidal structures
Efe Yazgan, Emre Taşci, Osman Bariş Malcioğlu, and 1 more author
J. of Molecular Structure: THEOCHEM 681 (2004) 231, Mar 2004
Electronic properties of five carbon nanotori (C170, C250, C360, C520, and C750) have been investigated by performing Extended-Hückel type calculations. Carbon nanotori considered is of Fonseca type having five-fold symmetry. It has been found that highest occupied molecular orbital–lowest occupied molecular orbital gaps of nanotori considered are very small, thus they may contain mobile electrons; pentagons and heptagons in the knee-regions act as an electron trap; and all the nanotori have a DOS distribution with common features.
2003
2003
-
Statistical Investigations of 1315 Radio Pulsars
O. H. Guseinov, E. Yazgan, S. Özkan, and 2 more authors
Astron. and Astrophys. Trans. 22 (2003) 301, Mar 2003
In this paper we have used the data of 1315 pulsars (Guseinov et al., 2002) for statistical analysis and showed the changes in pulsar parameters since the appearance of Taylor et al. (1996) catalog. Here we present the space distribution of pulsars, dispersion measures, distances from the galactic plane and from the Sun, electron density, luminosity distributions at 400 and 1400 MHz, the relations between luminosities of pulsars at 400 and 1400 MHz and the dependence of luminosity on age and on magnetic field. We also present the updated Pndash dotP diagram.
-
The Pulsar Luminosity Function
O. H. Guseinov, E. Yazgan, S. O. Tagieva, and 1 more author
Rev. Mex. Astron. y Astrofis. 39 (2003) 267, Jan 2003
We construct and examine the pulsar luminosity function using the new list which includes data for 1328 radio pulsars. In this work, the luminosity function for 1400 MHz is constructed for the first time. We also present an improved luminosity function for 400 MHz. The luminosity functions at 400 and 1400 MHz are compared. Also, the luminosity functions excluding the binary millisecond pulsars and the pulsars with low magnetic fields are constructed. It is found that the new luminosity function is considerably flatter in the low luminosity part for 400. 1400 MHz luminosity values of radio pulsars together with upper limits of 1400 MHz luminosity for anomalous X-ray pulsars and dim radio quiet neutron stars are presented as a function of both characteristic age and magnetic field. The implications of the pulsar luminosity function for these new kinds of neutron star are discussed.
-
Removal of the Difference Between Characteristic and Real Age in the Magnetar Model from the Analysis of Spectral Properties of AXPs, SGRs and DRQNSs
OKTAY H. GUSEINOV, ÖZGÜR TAŞKIN, EFE YAZGAN, and 1 more author
Int. J. of Mod. Phys. D 12 (2003) 1333, Jan 2003
We put together many observational data of SGRs and AXPs and analyze them with the main purpose to remove contradiction between the real age of these objects and their characteristic times of period change. This work indicates that SGRs and AXPs are neutron stars with magnetic fields up to 3×1014 G at birth, which is less than the possible value in the existing magnetar model. These neutron stars undergo star-quakes and reconnection of magnetic field occurs from time to time. As a result of these processes plasma is ejected from the NS and propeller mechanism starts to work. Due to the propeller effect ˙ P increases and τ decreases. Indeed, high ˙ P values are observed in SGRs and in half of the AXPs. Then, for a long time NS looses its activity, its ˙ P decreases, τ increases and rapid cooling begins. Each NS stage (AXP, SGR, dim) may occur once or several times until the spin period of the neutron star becomes P>10 12 s. At the transition period to the SGR and AXP stages, the magnetic field component perpendicular to the rotation axis may increase up to 2 3 times. Observational data and mainly the data of AXP1E1048-5937 and DRQNS RX J1308.8+2127 support this idea.
-
Do Young Neutron Stars Which Show Themselves as AXPs and SGRs Accrete?
S. O. Tagieva, E. Yazgan, and A. Ankay
Int. J. of Mod. Phys. D 12 (2003) 825, Jan 2003
We examined the fall-back disk models, and in general accretion, proposed to explain the properties of AXPs and SGRs. We checked the possibility of some gas remaining around the neutron star after a supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude that the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs and SGRs.
-
ON PERIOD AND BURST HISTORIES OF AXPs AND SGRs AND THE POSSIBLE EVOLUTION OF THESE OBJECTS ON THE \P -\dot P DIAGRAM
OKTAY H. GUSEINOV, EFE YAZGAN, AŞKIN ANKAY, and 1 more author
Int. J. of Mod. Phys. D 12 (2003) 1, Jan 2003
In this paper, timing data for anomalous X-ray pulsars and soft gamma repeaters are compiled. Timing properties of these objects are investigated. The effect of bursts of soft gamma repeaters on their period history is investigated. The \P -\dot P diagram for pulsars, X-ray binaries, anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet neutron stars is constructed. The possible evolutionary tracks for anomalous X-ray pulsars, soft gamma repeaters and dim radio quiet neutron stars are examined.
2002
2002
-
Analysis of the ASCA data of the intermediate polar YY Dra
E. Yazgan, and Ş. Balman
Astronomical Society of the Pacific Conf. Ser. 261 (2002) 177, Jan 2002
We present the ASCA archival data of the intermediate polar (IP) type cataclysmic variable YY Dra. We confirm the periodicities at 264.9 s and 529.3 s in the power spectrum. We have investigated the energetics of the pulse profiles and have found that the modulation depth (MD) increases with increasing energy at more than 3σ confidence level. We found that, the X-ray spectrum of YY Dra can be represented by a single or two-temperature model of VMEKAL/MEKAL or thermal bremsstrahlung.
-
Timing Characteristics of Intermediate Polar Type Cataclysmic Variables and Detailed Data Analysis on YY Draconis
Efe Yazgan
MSc Thesis, Jan 2002
In this thesis, an up-to-date review of intermediate type cataclysmic variables are made emphasizing timing characteristics. Fundamental timing analysis methods are introduced. Timing analysis on the intermediate polar AE Aquarii is per formed using three sets of ROSAT archival data. We have done timing and spec tral analysis on the intermediate polar YY Draconis using ASCA and ROSAT archival data sets. We have investigated the energetics of the pulse profiles. It is found that X-ray pulse profiles of YY Dra decreases with increasing energy. It is also found that the X-ray spectrum of YY Draconis can be represented by single or multitemperature bremsstrahlung and/or VMEKAL models. Lastly, the implication of our analysis is discussed in the light of current theory and observations.
2001
2001
-
Pulsar Spin-down by a Fallback Disk and the PPdot Diagram
Alpar, Aşkin Ankay, and Efe Yazgan
The Astrophysical Journal 557 (2001) 161, Aug 2001
Neutron stars may be surrounded by fallback disks formed from supernova core collapse. If the disk circumscribes the light cylinder, the neutron star will be an active radio pulsar spinning down under the propeller spin-down torque applied by the disk as well as the usual magnetic dipole radiation torque. Evolution across the P- diagram is very rapid when pulsar spin-down is dominated by the propeller torque. This explains the distribution of pulsars in the P-Pdot diagram.