Natural and Mathematical Sciences

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Open Access
Addendum: Measurement and QCD analysis of double-differential inclusive jet cross sections in proton-proton collisions at √s=13 TeV
(Springer, 2022-12-07) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The QCD analysis at NNLO is repeated by using the NNLO interpolation grids for the double-differential inclusive jet cross section [1], which were released after the journal publication of the original analysis. The NNLOJET calculation used to derive these grids is based on the leading-colour and leading-flavour-number approximation and does not include the most recent subleading colour contributions. However, these contributions were reported in ref. [2] to be very small in inclusive jet production, in particular for a jet size of R = 0.7. The grids also contain an estimate of the numerical integration uncertainty of around 1% or less. To account for point-to-point fluctuations, this uncertainty, after consultation with the authors of NNLOJET, has been increased by a factor of two; however, its impact in the fit is negligible. A comparison of the measurement with predictions using various PDFs is shown in figure 1. Although the PDF parametrisation remains identical, higher precision in PDF and QCD parameters is expected by using NNLO grids consistently in the QCD analysis. These new results supersede those obtained by using the k-factor technique.
Open Access
Analysis of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons in proton-proton collisions at s√ = 13 TeV
(Springer, 2022-06-03) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons is presented. The measurement is based on data collected in proton-proton collisions at s = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. The analysis uses the angular correlation between the decay planes of τ leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd τ Yukawa couplings is found to be −1 ± 19°, compared to an expected value of 0 ± 21° at the 68.3% confidence level. The data disfavour the pure CP-odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.
Open Access
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery
(Nature Research, 2022-11-02) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article.
Open Access
Axial-tensor meson family at T≠0
(Springer Nature, 2020-10-12) Süngü, J. Y.; Türkan, Arzu; Sertbakan, E.; Veliev, E. V.; Natural and Mathematical Sciences; TÜRKAN, Arzu
The mass and decay constants of rho(2), omega(2) and a missing member in the 2(--) nonet along with their first excited states are analyzed by the Thermal QCD sum rules approach, including QCD condensates up to dimension five. Mass and decay constant values of these mesons are stable from T = 0 up to T congruent to 120 MeV. However, after this threshold point, our numerical analyses indicates that they begin to diminish with increasing temperature. When we compare the hadronic parameters with their vacuum values, masses of these mesons and their first excited states decrease between (1-13%) from the PDG data and (10-26%) for the decay constants. However they diminish in the interval of (9-26%) and (2-34%) respectively with regards to Regge Trajectory Model data. We expect our numerical results will be confirmed by future heavy-ion collision experiments.
Open Access
Azimuthal anisotropy of dijet events in PbPb collisions at √sNN=5.02 TeV
(Springer, 2023-07-17) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb(-1). For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity (eta) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients v(n), n = 2-4 of these azimuthal distributions. The dijet v(n) values are extracted from long-range (1.5 < vertical bar Delta eta vertical bar < 2.5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v(2) values are observed which increase from central to more peripheral events, while the v(3) and v(4) values are consistent with zero within experimental uncertainties.
Open Access
Azimuthal correlations within exclusive dijets with large momentum transfer in photon-lead collisions
(American Physical Society, 2023-08-04) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at s NN = 5.02 TeV , corresponding to an integrated luminosity of 0.38 nb - 1 , collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.
Open Access
Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at √s = 7 and 8 TeV
(Springer, 2023-07-27) Aad, G.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton-proton collisions at centre-of-mass energies of 7 and 8TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron-muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb(-1) at root s = 7 TeV and about 20 fb(-1) at root s = 8TeV for each experiment. The combined cross-sections are determined to be 178.5 +/- 4.7 pb at root s = 7 TeV and 243.3(-5.9)(+6.0) pb at root s = 8TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined crosssections is determined to be R-8/7 = 1.363 +/- 0.032. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are m(t)(pole) = 173.4(-2.0)(+1.8) GeV and alpha s(m(Z)) = 0.1170(-0.0018)(+0.0021).
Open Access
Combination of the W boson polarization measurements in top quark decays using ATLAS and CMS data at √s = 8 TeV
(Springer, 2020-08-12) Aad, G.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb−1 for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal (F0), left-handed (FL), or right-handed (FR) polarizations. The resulting combined measurements of the polarization fractions are F0 = 0.693 ± 0.014 and FL = 0.315 ± 0.011. The fraction FR is calculated from the unitarity constraint to be FR = −0.008 ± 0.007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for F0 (FL) with respect to the most precise single measurement. A limit on anomalous right-handed vector (VR), and left- and right-handed tensor (gL, gR) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [−0.11, 0.16] for VR, [−0.08, 0.05] for gL, and [−0.04, 0.02] for gR, at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived.
Open Access
Combinations of single-top-quark production cross-section measurements and |f LV Vtb| determinations at √s = 7 and 8 TeV with the ATLAS and CMS experiments
(Springer, 2019-05-16) Aaboud, M.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at s = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb−1 at s = 7 TeV and 12.2 to 20.3 fb−1 at s = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at s = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at s = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at s = 8 TeV. The square of the magnitude of the CKM matrix element Vtb multiplied by a form factor fLV is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |Vtd|, |Vts| ≪ |Vtb|. All the |fLVVtb|2 determinations, extracted from individual ratios at s = 7 and 8 TeV, are combined, resulting in |fLVVtb| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.[Figure not available: see fulltext.].
Open Access
Computational investigation of dual filler-incorporated polymer membranes for efficient CO2 and H2 separation: MOF/COF/Polymer mixed matrix membranes
(American Chemical Society, 2023-01-26) Aydın, S.; Altintas, C.; Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Mixed matrix membranes (MMMs) composed of two different fillers such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) embedded into polymers provide enhanced gas separation performance. Since it is not possible to experimentally consider all possible combinations of MOFs, COFs, and polymers, developing computational methods is urgent to identify the best performing MOF-COF pairs to be used as dual fillers in polymer membranes for target gas separations. With this motivation, we combined molecular simulations of gas adsorption and diffusion in MOFs and COFs with theoretical permeation models to calculate H2, N2, CH4, and CO2 permeabilities of almost a million types of MOF/COF/polymer MMMs. We focused on COF/polymer MMMs located below the upper bound due to their low gas selectivity for five industrially important gas separations, CO2/N2, CO2/CH4, H2/N2, H2/CH4, and H2/CO2. We further investigated whether these MMMs could exceed the upper bound when a second type of filler, a MOF, was introduced into the polymer. Many MOF/COF/polymer MMMs were found to exceed the upper bounds showing the promise of using two different fillers in polymers. Results showed that for polymers having a relatively high gas permeability (≥104 barrer) but low selectivity (≤2.5) such as PTMSP, addition of the MOF as the second filler can have a dramatic effect on the final gas permeability and selectivity of the MMM. Property-performance relations were analyzed to understand how the structural and chemical properties of the fillers affect the permeability of the resulting MMMs, and MOFs having Zn, Cu, and Cd metals were found to lead to the highest increase in gas permeability of MMMs. This work highlights the significant potential of using COF and MOF fillers in MMMs to achieve better gas separation performances than MMMs with one type of filler, especially for H2 purification and CO2 capture applications.
Open Access
Convergence of a linearly regularized nonlinear wave equation to the p-system
(TÜBİTAK, 2023) Erbay, Hüsnü Ata; Erbay, Saadet; Erkip, A. K.; Natural and Mathematical Sciences; ERBAY, Hüsnü Ata; ERBAY, Saadet
We consider a second-order nonlinear wave equation with a linear convolution term. When the convolution operator is taken as the identity operator, our equation reduces to the classical elasticity equation which can be written as a p-system of first-order differential equations. We first establish the local well-posedness of the Cauchy problem. We then investigate the behavior of solutions to the Cauchy problem in the limit as the kernel function of the convolution integral approaches to the Dirac delta function, that is, in the vanishing dispersion limit. We consider two different types of the vanishing dispersion limit behaviors for the convolution operator depending on the form of the kernel function. In both cases, we show that the solutions converge strongly to the corresponding solutions of the classical elasticity equation.
Open Access
Erratum to: Search for heavy Higgs bosons decaying to a top quark pair in proton-proton collisions at s√ = 13 TeV
(Springer Nature, 2022-03) Sirunyan, A. M.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
In figure 7 of the original publication, the label of the y axis should have been (Formula presented.)”. The corrected version is shown in figure 1. Accordingly, the text pointing to the figure should read “figure 7 shows scans of (Formula presented.) for this hypothesis, as a function of the coupling modifier gAtt-”. © The Author(s).
Open Access
Erratum: Measurement of prompt and nonprompt charmonium suppression in PbPb collisions at 5.02 TeV
(Springer, 2023-02) Sirunyan, A. M.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
In Fig. 3, the y axis titles were mistakenly written showing a single-differential cross section in either dimuon (Formula presented.) or rapidity, when in fact the cross section is normalized by both the (Formula presented.) and rapidity ranges used for a given measurement point. The corrected version is shown in the new Fig. 3 provided below. (Figure presented.) Differential cross section of prompt (Formula presented.) mesons (left) and (Formula presented.) mesons from b hadrons (nonprompt (Formula presented.) ) (right) decaying into two muons as a function of dimuon (Formula presented.) (upper) and rapidity (lower) in pp and (Formula presented.) collisions. The (Formula presented.) cross sections are normalised by (Formula presented.) for direct comparison. The bars (boxes) represent statistical (systematic) point-by-point uncertainties, while global uncertainties are written on the plots. © 2023, CERN for the benefit of the CMS Collaboration.
Open Access
Evidence for WW/WZ vector boson scattering in the decay channel ℓνqq produced in association with two jets in proton-proton collisions at √s = 13 TeVeV
(Elsevier, 2022-11-10) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Evidence is reported for electroweak (EW) vector boson scattering in the decay channel ℓνqq of two weak vector bosons WV (V=W or Z), produced in association with two parton jets. The search uses a data set of proton-proton collisions at 13 TeV collected with the CMS detector during 2016–2018 with an integrated luminosity of 138fb−1. Events are selected requiring one lepton (electron or muon), moderate missing transverse momentum, two jets with a large pseudorapidity separation and a large dijet invariant mass, and a signature consistent with the hadronic decay of a W/Z boson. The cross section is computed in a fiducial phase space defined at parton level requiring all parton transverse momenta pT>10GeV and at least one pair of outgoing partons with invariant mass mqq>100GeV. The measured and expected EW WV production cross sections are 1.90−0.46+0.53 pb and 2.23−0.11+0.08(scale)±0.05(PDF) pb, respectively, where PDF is the parton distribution function. The observed EW signal strength is μEW=0.85±0.12(stat)−0.17+0.19(syst), corresponding to a signal significance of 4.4 standard deviations with 5.1 expected, and it is measured keeping the quantum chromodynamics (QCD) associated diboson production fixed to the standard model prediction. This is the first evidence of vector boson scattering in the ℓνqq decay channel at LHC. The simultaneous measurement of the EW and QCD associated diboson production agrees with the standard model prediction.
Open Access
Evidence for X(3872) in Pb-Pb collisions and studies of its prompt production at √s NN = 5.02 TeV
(American Physical Society, 2022-01-19) Sirunyan, A. M.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of √ s NN = 5.02 TeV per nucleon pair, using the decay chain X ( 3872 ) → J / ψ π + π − → μ + μ − π + π − . The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 nb − 1 . The measurement is performed in the rapidity and transverse momentum ranges | y | < 1.6 and 15 < p T < 50 GeV / c . The significance of the inclusive X(3872) signal is 4.2 standard deviations. The prompt X(3872) to ψ 2 S yield ratio is found to be ρ Pb − Pb = 1.08 ± 0.49 ( stat ) ± 0.52 ( syst ) , to be compared with typical values of 0.1 for p p collisions. This result provides a unique experimental input to theoretical models of the X(3872) production mechanism, and of the nature of this exotic state.
Open Access
First measurement of the forward rapidity gap distribution in pPb collisions at √s NN = 8.16 TeV
(American Physical Society, 2023-11-20) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
For the first time at LHC energies, the forward rapidity gap spectra from proton-lead collisions for both proton and lead dissociation processes are presented. The analysis is performed over 10.4 units of pseudorapidity at a center-of-mass energy per nucleon pair of Formula Presented, almost 300 times higher than in previous measurements of diffractive production in proton-nucleus collisions. For lead dissociation processes, which correspond to the pomeron-lead event topology, the epos-lhc generator predictions are a factor of 2 below the data, but the model gives a reasonable description of the rapidity gap spectrum shape. For the pomeron-proton topology, the epos-lhc, qgsjet ii, and hijing predictions are all at least a factor of 5 lower than the data. The latter effect might be explained by a significant contribution of ultraperipheral photoproduction events mimicking the signature of diffractive processes. These data may be of significant help in understanding the high energy limit of quantum chromodynamics and for modeling cosmic ray air showers.
Open Access
First measurement of the top quark pair production cross section in proton-proton collisions at √s = 13.6 TeV
(Springer, 2023-08-30) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
The first measurement of the top quark pair (t (t) over bar) production cross section in proton-proton collisions at root s = 13.6TeV is presented. Data recorded with the CMS detector at the CERN LHC in Summer 2022, corresponding to an integrated luminosity of 1.21 fb(-1), are analyzed. Events are selected with one or two charged leptons (electrons or muons) and additional jets. A maximum likelihood fit is performed in event categories defined by the number and flavors of the leptons, the number of jets, and the number of jets identified as originating from b quarks. An inclusive t (t) over bar production cross section of 881 +/- 23 (stat + syst) +/- 20 (lumi) pb is measured, in agreement with the standard model prediction of 924(-40)(+32) pb.
Open Access
First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at √s = 13 TeV
(American Physical Society, 2022-06-28) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp→pγγp with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb-1 collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% confidence level are |ζ1|<2.9×10-13 GeV-4 and |ζ2|[removed]
Open Access
Impact of a thermal medium on newly observed Zcs(3985) resonance and its b-partner
(Springer, 2022-05-17) Süngü, J. Y.; Türkan, Arzu; Sundu, H.; Veliev, E. V.; Natural and Mathematical Sciences; TÜRKAN, Arzu
Motivated by the very recent discovery of the strange hidden-charm exotic state Zcs(3985) by the BESIII Collaboration, we study the possible interpretation of this exotic state the both at T= 0 and T≠ 0. We analytically compute the mass and meson-current coupling constant of this resonance with spin-parity JP= 1 + at finite temperature approximation up to the sixth order of the thermal operator dimension including non-perturbative contributions. Extracting thermal mass and meson-current coupling constant sum rules, the modifications on properties of the Zcs(3985) state in hot medium are determined. As a by-product, the hadronic parameters of the bottom partner of Zcs(3985) is estimated as well. The search for temperature effects on the hadronic parameters of the hidden-charm meson Zcs(3985) and the bottom partner enable us to understand the phase transitions, chiral symmetry breaking, and the properties of hot-dense matter in QCD. Moreover, the full width of the resonance Zcs(3985) is calculated as (12.0±0.8)MeV using the strong decay in the tetraquark picture. Results for width and mass are in reasonable agreement with existing experimental data and results of other theoretical works. The information obtained about the parameters of the considered states is useful for experimental investigations of exotic mesons.
Open Access
Inclusive and differential cross section measurements of single top quark production in association with a Z boson in proton-proton collisions at s√ = 13 TeV
(Springer, 2022-02-14) Tumasyan, A.; Işıldak, Bora; The CMS Collaboration; Natural and Mathematical Sciences; IŞILDAK, Bora
Inclusive and differential cross sections of single top quark production in association with a Z boson are measured in proton-proton collisions at a center-of-mass energy of 13 TeV with a data sample corresponding to an integrated luminosity of 138 fb−1 recorded by the CMS experiment. Events are selected based on the presence of three leptons, electrons or muons, associated with leptonic Z boson and top quark decays. The measurement yields an inclusive cross section of 87.9−7.3+7.5(stat)−6.0+7.3(syst) fb for a dilepton invariant mass greater than 30 GeV, in agreement with standard model (SM) calculations and represents the most precise determination to date. The ratio between the cross sections for the top quark and the top antiquark production in association with a Z boson is measured as 2.37−0.42+0.56(stat)−0.13+0.27(syst). Differential measurements at parton and particle levels are performed for the first time. Several kinematic observables are considered to study the modeling of the process. Results are compared to theoretical predictions with different assumptions on the source of the initial-state b quark and found to be in agreement, within the uncertainties. Additionally, the spin asymmetry, which is sensitive to the top quark polarization, is determined from the differential distribution of the polarization angle at parton level to be 0.54 ± 0.16 (stat) ± 0.06 (syst), in agreement with SM predictions.