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Absolute measurements of branching fractions of Cabibbo-suppressed hadronic D0(+) decays involving multiple pions
(AMER PHYSICAL SOC, 2022) Ablikim, M.; Achasov, M. N.; Adlarson, Patrik; Albrecht, Malte; Aliberti, Riccardo; Çetin, Serkant Ali; Kolcu, Onur Buğra
By analyzing e(+)e(-) annihilation data with an integrated luminosity of 2.93 fb(-1) collected at the center-of-mass energy root s = 3.773 GeV with the BESIII detector, we present the first absolute measurements of the branching fractions of twenty Cabibbo-suppressed hadronic D0(+) decays involving multiple pions. The highest four branching fractions obtained are B(D-0 -> pi(+)pi(-)pi(0)) = (1.343 +/- 0.013(stat) +/- 0.016(syst))%, B(D-0 -> pi(+)pi(-)2 pi(0)) = (1.002 +/- 0.019(stat )+/- 0.024(syst))%, B(D-0 -> 2 pi(+)pi(-)pi(0))=(1.165 +/- 0.021(stat) +/- 0.021(sy)(st))%, and B(D+ -> 2 pi(+)pi(-)pi(0)). (1.074 +/- 0.040(stat) 0.030(syst))%. The CP asymmetries for the six decays with highest signal yields are also determined and found to be compatible with zero.
Amplitude analysis and branching fraction measurement of the decay D+ ? KS0?+?0?0
(Springer, 2023) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ai, X. C.; Aliberti, R.; Amoroso, A.; Çetin, Serkant Ali
Using 2.93 fb(-1) of e(+)e(-) collision data collected with the BESIII detector at the center-of-mass energy 3.773 GeV, we perform the first amplitude analysis of the decay D+ -> K-S(0)pi(+)pi(0)pi(0) and determine the relative magnitudes and phases of different intermediate processes. The absolute branching fraction of D+ -> K-S(0)pi(+)pi(0)pi(0) is measured to be (2.888 +/- 0.058(stat.) +/- 0.069(syst.))%. The dominant intermediate processes are D+ -> K(S)(0)a(1)(1260)(+)(-> rho(+)pi(0)) and D+ -> K-*0 rho(+), with branching fractions of (8.66 +/- 1.04(stat.) +/- 1.39(syst.)) x 10(-3) and (9.70 +/- 0.81(stat.) +/- 0.53(syst.)) x 10(-3), respectively.
Amplitude analysis and branching fraction measurement of the decay D-s(+) -> K+pi(+)pi(-)
(SPRINGER, 2022) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Çetin, Serkant Ali; Kolcu, Onur Buğra
Using 6.32 fb(-1) of e(+)e(-) collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay D-s(+) -> K+pi(+)pi(-) and determine the amplitudes of the various intermediate states. The absolute branching fraction of D-s(+) -> K+pi(+)pi(-) is measured to be (6.11 +/- 0 .18(stat.) +/- 0.11(syst.)) x 10(-3). The branching fractions of the dominant intermediate processes D-s(+) -> K+C+rho(0), rho(0) -> pi(+)pi(-) and D-s(+) -> K*(892)(0)pi(+), K*(892)(0) -> K+pi(-) are determined to be (1.96 +/- 0.19(stat.) +/- 0.23(syst.)) x 10(-3) and (1.85 +/- 0.12(stat.) +/- 0.13(syst.)) x 10(-3), respectively. The intermediate resonances f(0)(500), f(0)(980), and f(0)(1370) are observed for the first time in this channel.
Amplitude analysis of Ds+ ? ?+ ?- ?+
(Amer Physical Soc, 2022) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Aliberti, R.; Çetin, Serkant Ali
Utilizing the data set corresponding to an integrated luminosity of 3.19 fb(-1) collected by the BESIII detector at a center-of-mass energy of 4.178 GeV, we perform an amplitude analysis of the D-s(+) -> pi(+) pi(-) pi(+) decay. The sample contains 13,797 candidates with a signal purity of similar to 80%. The amplitude and phase of the contributing pi pi S wave are measured based on a quasi-model-independent approach, along with the amplitudes and phases of the P and D waves parametrized by Breit-Wigner models. The fit fractions of different intermediate decay channels are also reported.
Anomaly detection search for new resonances decaying into a Higgs boson and a generic new particle X in hadronic final states using ?s=13 TeV pp collisions with the ATLAS detector
(Amer Physical Soc, 2023) Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
A search is presented for a heavy resonance Y decaying into a Standard Model Higgs boson H and a new particle X in a fully hadronic final state. The full Large Hadron Collider run 2 dataset of proton-proton collisions at root s =13 TeV collected by the ATLAS detector from 2015 to 2018 is used and corresponds to an integrated luminosity of 139 fb(-1). The search targets the high Y-mass region, where the H and X have a significant Lorentz boost in the laboratory frame. A novel application of anomaly detection is used to define a general signal region, where events are selected solely because of their incompatibility with a learned background-only model. It is constructed using a jet-level tagger for signal-model-independent selection of the boosted X particle, representing the first application of fully unsupervised machine learning to an ATLAS analysis. Two additional signal regions are implemented to target a benchmark X decay into two quarks, covering topologies where the X is reconstructed as either a single large-radius jet or two small-radius jets. The analysis selects Higgs boson decays into bb, and a dedicated neural-network-based tagger provides sensitivity to the boosted heavy-flavor topology. No significant excess of data over the expected background is observed, and the results are presented as upper limits on the production cross section sigma(pp -> Y -> XH -> qqbb) for signals with m(Y) between 1.5 and 6 TeV and m(X) between 65 and 3000 GeV.
ATLAS flavour-tagging algorithms for the LHC Run 2 pp collision dataset
(Springer, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
The flavour-tagging algorithms developed by the AvTLAS Collaboration and used to analyse its dataset of root s = 13 TeV pp collisions from Run 2 of the Large Hadron Collider are presented. These new tagging algorithms are based on recurrent and deep neural networks, and their performance is evaluated in simulated collision events. These developments yield considerable improvements over previous jet-flavour identification strategies. At the 77% b-jet identification efficiency operating point, light-jet (charm-jet) rejection factors of 170 (5) are achieved in a sample of simulated Standard Model t (t) over bar events; similarly, at a c-jet identification efficiency of 30%, a light-jet (b-jet) rejection factor of 70 (9) is obtained.
Author Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery (Nature, (2022), 607, 7917, (52-59), 10.1038/s41586-022-04893-w)
(Nature Research, 2023) Aad, G.; Abbott, B.; Abbott, D.C.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Çetin, Serkant Ali
Correction to: Nature Published online 4 July 2022 In the version of this article initially published, the ATLAS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article. © 2023, The Author(s).
Calibration of the light-flavour jet mistagging efficiency of the b-tagging algorithms with Z plus jets events using 139 fb-1 of ATLAS proton-proton collision data at ?s=13 TeV
(Springer, 2023) Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
The identification of b-jets, referred to as b-tagging, is an important part of many physics analyses in the ATLAS experiment at the Large Hadron Collider and an accurate calibration of its performance is essential for high-quality physics results. This publication describes the calibration of the light-flavour jet mistagging efficiency in a data sample of proton-proton collision events at root s = 13 TeV corresponding to an integrated luminosity of 139 fb(-1). The calibration is performed in a sample of Z bosons produced in association with jets. Due to the low mistagging efficiency for light-flavour jets, a method which uses modified versions of the b-tagging algorithms referred to as flip taggers is used in this work. A fit to the jet-flavour-sensitive secondary-vertex mass is performed to extract a scale factor from data, to correct the light-flavour jet mistagging efficiency in Monte Carlo simulations, while simultaneously correcting the b-jet efficiency. With this procedure, uncertainties coming from the modeling of jets from heavy-flavour hadrons are considerably lower than in previous calibrations of the mistagging scale factors, where they were dominant. The scale factors obtained in this calibration are consistent with unity within uncertainties.
CAST and more than CAST; A Dark Sector Probe for 20+ Years
(Sissa Medialab Srl, 2024) Çetin, Serkant Ali
This paper is a review of the CERN Axion Solar Telescope (CAST) experiment. We summarize the CAST experimental results, give highlights on the history of CAST and discuss its evolution into various different probes in the dark sector beyond its initial goals with a timeline. The results, achievements and challenges throughout the lifetime of CAST are presented. © Copyright owned by the author(s).
Charged-hadron production in pp, p+Pb, Pb+Pb, and Xe+Xe collisions at ?sNN = 5 TeV with the ATLAS detector at the LHC
(Springer Science and Business Media Deutschland GmbH, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant Ali
This paper presents measurements of charged-hadron spectra obtained in pp, p+Pb, and Pb+Pb collisions at s or sNN = 5.02 TeV, and in Xe+Xe collisions at sNN = 5.44 TeV. The data recorded by the ATLAS detector at the LHC have total integrated luminosities of 25 pb?1, 28 nb?1, 0.50 nb?1, and 3 ?b?1, respectively. The nuclear modification factors RpPb and R AA are obtained by comparing the spectra in heavy-ion and pp collisions in a wide range of charged-particle transverse momenta and pseudorapidity. The nuclear modification factor RpPb shows a moderate enhancement above unity with a maximum at p T ? 3 GeV; the enhancement is stronger in the Pb-going direction. The nuclear modification factors in both Pb+Pb and Xe+Xe collisions feature a significant, centrality-dependent suppression. They show a similar distinct p T-dependence with a local maximum at p T ? 2 GeV and a local minimum at p T ? 7 GeV. This dependence is more distinguishable in more central collisions. No significant |?|-dependence is found. A comprehensive comparison with several theoretical predictions is also provided. They typically describe R AA better in central collisions and in the p T range from about 10 to 100 GeV. [Figure not available: see fulltext.] © 2023, The Author(s).
Combination of searches for invisible decays of the Higgs boson using 139 fb?1 of proton-proton collision data at s=13 TeV collected with the ATLAS experiment
(Elsevier B.V., 2023) Aad, G.; Abbott, B.; Abeling, K.; Abidi, S.H.; Aboulhorma, A.; Abramowicz, H.; Çetin, Serkant Ali
Many extensions of the Standard Model predict the production of dark matter particles at the LHC. Sufficiently light dark matter particles may be produced in decays of the Higgs boson that would appear invisible to the detector. This Letter presents a statistical combination of searches for H?invisible decays where multiple production modes of the Standard Model Higgs boson are considered. These searches are performed with the ATLAS detector using 139 fb?1 of proton–proton collisions at a centre–of–mass energy of [Formula presented] at the LHC. In combination with the results at [Formula presented] and [Formula presented], an upper limit on the H?invisible branching ratio of 0.107 (0.077) at the 95% confidence level is observed (expected). These results are also interpreted in the context of models where the 125 GeV Higgs boson acts as a portal to dark matter, and limits are set on the scattering cross-section of weakly interacting massive particles and nucleons. © 2023 The Author(s)
Combination of searches for resonant higgs boson pair production using 𝑝⁢𝑝 collisions at √𝑠=13 TeV with the ATLAS detector
(American Physical Society, 2024) Filmer, E.K.; Grant, C.M.; Jackson, P; Beddal, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, Zekeriya
A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to Formula Presented of Formula Presented collision data at Formula Presented recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: Formula Presented, Formula Presented, and Formula Presented. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches. © 2024 CERN, for the ATLAS Collaboration.
Combined Measurement of the Higgs Boson Mass from the H ? ?? and H ? ZZ* ? 4l Decay Channels with the ATLAS Detector Using ?s=7, 8, and 13 TeV pp Collision Data
(Amer Physical Soc, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
A measurement of the mass of the Higgs boson combining the H -> ZZ* -> 4l and H -> gamma gamma decay channels is presented. The result is based on 140 fb(-1) of proton-proton collision data collected by the ATLAS detector during LHC run 2 at a center-of-mass energy of 13 TeV combined with the run 1 ATLAS mass measurement, performed at center-of-mass energies of 7 and 8 TeV, yielding a Higgs boson mass of 125.11 +/- 0.09(stat) +/- 0.06(syst) = 125.11 +/- 0.11 GeV. This corresponds to a 0.09% precision achieved on this fundamental parameter of the Standard Model of particle physics.
Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS
(Elsevier, 2023) Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
Parton energy loss in the quark-gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb-1 of Pb+Pb data and 260 pb-1 of pp data, both at root sNN = 5.02 TeV, with the ATLAS detector. The process pp -> gamma +jet+X and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (pT) above 50 GeV and reported as a function of jet pT. This selection results in a sample of jets with a steeply falling pT distribution that are mostly initiated by the showering of quarks. The pp and Pb+Pb measurements are used to report the nuclear modification factor, RAA, and the fractional energy loss, Sloss, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The RAA and Sloss values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.
Constraints on Higgs boson production with large transverse momentum using H -> b(b)over-bar decays in the ATLAS detector
(AMER PHYSICAL SOC, 2022) Aad, G.; Abbott, B.; Abbott, D. C.; Abud, A. Abed; Çetin, Serkant Ali; Öztürk, Sertaç
This paper reports constraints on Higgs boson production with transverse momentum above 1 TeV. The analyzed data from proton-proton collisions at a center-of-mass energy of 13 TeV were recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018 and correspond to an integrated luminosity of 136 fb(-1.) Higgs bosons decaying into b (b) over bar are reconstructed as single large-radius jets recoiling against a hadronic system and are identified by the experimental signature of two b-hadron decays. The experimental techniques are validated in the same kinematic regime using the Z -> b (b) over bar process. The 95% confidence-level upper limit on the cross section for Higgs boson production with transverse momentum above 450 GeV is 115 fb, and above 1 TeV it is 9.6 fb. The Standard Model cross section predictions for a Higgs boson with a mass of 125 GeV in the same kinematic regions are 18.4 fb and 0.13 fb, respectively.
Constraints on spin-0 dark matter mediators and invisible Higgs decays using ATLAS 13 TeV pp collision data with two top quarks and missing transverse momentum in the final state
(Springer, 2023) Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
This paper presents a statistical combination of searches targeting final states with two top quarks and invisible particles, characterised by the presence of zero, one or two leptons, at least one jet originating from a b-quark and missing transverse momentum. The analyses are searches for phenomena beyond the Standard Model consistent with the direct production of dark matter in pp collisions at the LHC, using 139 fb(-1) of data collected with the ATLAS detector at a centre-of-mass energy of 13 TeV. The results are interpreted in terms of simplified dark matter models with a spin-0 scalar or pseudoscalar mediator particle. In addition, the results are interpreted in terms of upper limits on the Higgs boson invisible branching ratio, where the Higgs boson is produced according to the StandardModel in associationwith a pair of top quarks. For scalar (pseudoscalar) dark matter models, with all couplings set to unity, the statistical combination extends the mass range excluded by the best of the individual channels by 50 (25) GeV, excluding mediator masses up to 370 GeV. In addition, the statistical combination improves the expected coupling exclusion reach by 14% (24%), assuming a scalar (pseudoscalar) mediator mass of 10 GeV. An upper limit on the Higgs boson invisible branching ratio of 0.38 (0.30(-0.09)(+0.13)) is observed (expected) at 95% confidence level.
Constraints on the Higgs boson self-coupling from single- and double-Higgs production with the ATLAS detector using pp collisions at?s=13 TeV
(Elsevier, 2023) Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
Constraints on the Higgs boson self-coupling are set by combining double-Higgs boson analyses in the bb over bar bb over bar , bb over bar & tau;+& tau;- and bb over bar & gamma; & gamma; decay channels with single-Higgs boson analyses targeting the & gamma;& gamma;, Z Z*, W W *, & tau;+& tau;- and bb over bar decay channels. The data used in these analyses were recorded by the ATLAS detector at the LHC in proton-proton collisions at & RADIC;s = 13 TeV and correspond to an integrated luminosity of 126-139 fb-1. The combination of the double-Higgs analyses sets an upper limit of & mu;HH < 2.4 at 95% confidence level on the double-Higgs production cross-section normalised to its Standard Model prediction. Combining the single-Higgs and double-Higgs analyses, with the assumption that new physics affects only the Higgs boson self-coupling (& lambda;HHH), values outside the interval -0.4 < & kappa;& lambda; = (& lambda;HHH/& lambda;SM H H H ) < 6.3 are excluded at 95% confidence level. The combined single-Higgs and double-Higgs analyses provide results with fewer assumptions, by adding in the fit more coupling modifiers introduced to account for the Higgs boson interactions with the other Standard Model particles. In this relaxed scenario, the constraint becomes -1.4 < & kappa;& lambda; < 6.1 at 95% CL. & COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.
Correlations between flow and transverse momentum in Xe plus Xe and Pb plus Pb collisions at the LHC with the ATLAS detector: A probe of the heavy-ion initial state and nuclear deformation
(Amer Physical Soc, 2023) Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Çetin, Serkant Ali
The correlations between flow harmonics v(n) for n = 2, 3, and 4 and mean transverse momentum [pT] in Xe-129 + Xe-129 and Pb-208 + Pb-208 collisions at root s = 5.44 and 5.02 TeV, respectively, are measured using charged particles with the ATLAS detector. The correlations are potentially sensitive to the shape and size of the initial geometry, nuclear deformation, and initial momentum anisotropy. The effects from nonflow and centrality fluctuations are minimized, respectively, via a subevent cumulant method and an event-activity selection based on particle production at very forward rapidity. The v(n)-[p(T)] correlations show strong dependencies on centrality, harmonic number n, pT, and pseudorapidity range. Current models qualitatively describe the overall centrality -and system-dependent trends but fail to quantitatively reproduce all features of the data. In central collisions, where models generally show good agreement, the v(2)-[p(T)] correlations are sensitive to the triaxiality of the quadruple deformation. Comparison of the model with the Pb + Pb and Xe + Xe data confirms that the Xe-129 nucleus is a highly deformed triaxial ellipsoid that has neither a prolate nor oblate shape. This provides strong evidence for a triaxial deformation of the Xe-129 nucleus from high-energy heavy-ion collisions.
Cross section measurements of the e(+)e(-) -> D*D+*(-) and e(+)e(-) -> D*D-+(-) processes at center-of-mass energies from 4.085 to 4.600 GeV
(SPRINGER, 2022) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Albrecht, M.; Çetin, Serkant Ali; Kolcu, Onur Buğra
The Born cross sections of the e(+)e(-) -> D*D+*(-) and e(+)e(-) -> D*D-+(-) processes are measured using e(+)e(-) collision data collected with the BESIII experiment at center-of-mass energies from 4.085 to 4.600 GeV, corresponding to an integrated luminosity of 15.7 fb(-1). The results are consistent with and more precise than the previous measurements by the Belle, Babar and CLEO collaborations. The measurements are essential for understanding the nature of vector charmonium and charmonium-like states.
Cross section measurements of the processes e(+)e(-) -> omega pi(0) and omega eta at center-of-mass energies between 3.773 and 4.701 GeV
(SPRINGER, 2022) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Çetin, Serkant Ali; Kolcu, Onur Buğra
The Born cross sections of the processes e(+)e(-) -> omega pi(0) and e(+)e(-) -> omega eta are measured at center-of-mass energies between 3.773 and 4.701 GeV using a total integrated luminosity of 22.7 fb(-1) collected with the BESIII detector operating at the BEPCII collider. A simple s(-n) dependence for the continuum process can describe the measured Born cross sections. No significant contributions from the psi(4160), Y(4230), Y(4360), psi(4415), Y(4660) resonances are found, which indicates relative small branching fractions for these resonances into the omega pi(0) and omega eta final states.

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