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86,772
result(s) for
"hadron"
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Measurement of light-by-light scattering and search for axion-like particles with 2.2 nb(-1) of Pb+Pb data with the ATLAS detector
This paper describes a measurement of light-by-light scattering based on Pb+Pb collision data recorded by the ATLAS experiment during Run 2 of the LHC. The study uses 2.2 nb(-1) of integrated luminosity collected in 2015 and 2018 at root sNN = 5.02TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy E-T(gamma) > 2.5 GeV, pseudorapidity vertical bar eta(gamma)vertical bar < 2.37, diphoton invariant mass m(gamma gamma) > 5 GeV, and with small diphoton transverse momentum and diphoton acoplanarity. The integrated and differential fiducial cross sections are measured and compared with theoretical predictions. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles. This result provides the most stringent limits to date on axion-like particle production for masses in the range 6-100 GeV. Cross sections above 2 to 70 nb are excluded at the 95% CL in that mass interval.
Journal Article
Searches for the Zγ decay mode of the Higgs boson and for new high-mass resonances in pp collisions at √s = 13 TeV with the ATLAS detector
A
bstract
This article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to
Z
γ, exploiting
Z
boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb
−1
of
pp
collisions at
s
=
13
recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model
pp
→
H
→
Z
γ production and decay) upper limit on the production cross section times the branching ratio for
pp
→
H
→
Z
γ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level.
Journal Article
Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb(-1) of √s=13 TeV pp collision data with the ATLAS detector
A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of root s = 13 TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb(-1). The results are interpreted in the context of various R-parity-conserving models where squarks and gluinos are produced in pairs or in association and a neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.30 TeV for a simplified model containing only a gluino and the lightest neutralino, assuming the latter is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.85 TeV are excluded if the lightest neutralino is massless. These limits extend substantially beyond the region of supersymmetric parameter space excluded previously by similar searches with the ATLAS detector.
Journal Article
Exploring the Υ ( 6 S ) → χ b J ϕ and Υ ( 6 S ) → χ b J ω hidden-bottom hadronic transitions
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image)In this work, we investigate the hadronic loop contributions to the ... along with ... transitions. We predict that the branching ratios of ..., ... and ... are (0.68–4.62) ..., (0.50–3.43) ..., and (2.22–15.18) ..., respectively, and those of ..., ... and ... are (0.15–2.81) ..., (0.63–11.68) ..., and (1.08–20.02) ..., respectively. Especially, some typical ratios, which reflect the relative magnitudes of the predicted branching ratios, are given, i.e., for ... transitions, ..., ..., and ..., and for ... transitions, ..., ..., and ... With the running of BelleII in the near future, experimental measurement of these two kinds of transitions will be a potential research issue.
Journal Article
Chemical freeze-out of light nuclei in high energy nuclear collisions and resolution of the hyper-triton chemical freeze-out puzzle
We present a summary of the recent results obtained with the novel hadron resonance gas model with the multicomponent hard-core repulsion which is extended to describe the mixtures of hadrons and light (anti-, hyper-)nuclei. A very accurate description is obtained for the hadronic and the light nuclei data measured by STAR at the collision energy sNN=200GeV and by ALICE at sNN=2.76TeV. The most striking result discussed here is that for the most probable chemical freeze-out scenario for the STAR energy the found parameters allow us to reproduce the values of the experimental ratios S3 and S¯3 without fitting.
Journal Article