Search for resonant W Z production in the W Z → l ν l ′ l ′ channel in ( s ) = 7 TeV p p collisions with the ATLAS detector
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G. Aad↗
SEARCH · Engineering Papers
Results for “resonance production”
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DAISEY - An efficient program for production of neutron pseudo resonance parameter chains in the unresolved energy region
Computer program for production of neutron pseudo resonance parameter chains in unresolved energy region
Semler, T. T.↗
Analysis of ion-molecule reactions in allene and propyne by ion cyclotron resonance
Thermal product distributions and energy dependencies of ion-molecule reactions in allene and propyne, using ion cyclotron resonance
Bowers, M. T.↗
Pion production via isobar giant resonance formation and decay
A spin, isotopic-spin formalism for the production of pions due to decays of isobar giant resonances formed in peripheral heavy-ion collisions is presented. The projectile nucleus isobar giant resonance state is assumed to coherently form and then incoherently decay to produce the pions. Total spin and isotopic spin for the system are conserved through the concomitant excitation of the target nucleus to an isobaric analog giant resonance state. Comparisons of the predicted total pion cross sections, over a range of energies, are made with heavy-ion pion data.
Townsend, L. W.↗
Search for Non-resonant Higgs Boson Pair Production in the Four Bottom Quark Decay Channel With the CMS Experiment
This dissertation presents a search for non-resonant Higgs boson pair production, focusing on the four bottom quark decay channel. It explores the gluon fusion and vector boson fusion production mechanisms. The analysis is performed with a dataset of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS detector at the LHC, corresponding to an integrated luminosity of around 138 inverse femtobarns. Innovative techniques in the areas of object identification, event categorization, signal identification, and background modeling are used to maximize the analysis sensitivity. No excess of signal events are observed relative to the background-only expectation, and 95% CL upper limits on the production cross section are set. The observed upper limit on the standard model production cross section is set at 3.6 times the theoretical expectation. At the time of writing this dissertation, it is the most stringent constraint at the LHC from an individual channel. Furthermore, the observed constraint on the coupling modifier of the Higgs boson self-interaction is set between -2.3 and 9.4. The observed constraint on the coupling modifier of the di-vector-boson-di-Higgs-boson interaction is set between -0.1 and 2.2.
Guerrero Ibarra, Guerrero Fernando↗
Search for non-resonant Higgs boson pair production in the $2b+2\ell +{E}_{\textrm{T}}^{\textrm{miss}}$ final state in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
A search for non-resonant Higgs boson pair (HH) production is presented, in which one of the Higgs bosons decays to a b-quark pair ($b\bar{b}$) and the other decays to WW * , ZZ * , or τ + τ – , with in each case a final state with ℓ + ℓ – + neutrinos (ℓ = e, μ). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb –1 , are used in this analysis. Events are selected to have exactly two b-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the HH events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter κ λ and the quadrilinear coupling parameter κ 2V are each separately constrained by this analysis to be within the ranges [–6.2, 13.3] and [–0.17, 2.4], respectively, at 95% confidence level, when all other parameters are fixed.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for Higgs boson pair production in association with a vector boson in pp collisions at $\sqrt{s}=13\,\text {TeV}$ with the ATLAS detector
This paper reports a search for Higgs boson pair (hh) production in association with a vector boson ($W\; {\text {o}r}\; Z$) using 139 fb –1 of proton–proton collision data at $\sqrt{s}=13\,\text {TeV}$ recorded with the ATLAS detector at the Large Hadron Collider. The search is performed in final states in which the vector boson decays leptonically ($W\rightarrow \ell \nu ,\, Z\rightarrow \ell \ell ,\nu \nu$ with $\ell =e, \mu$) and the Higgs bosons each decay into a pair of b-quarks. It targets Vhh signals from both non-resonant hh production, present in the Standard Model (SM), and resonant hh production, as predicted in some SM extensions. A 95% confidence-level upper limit of 183 (87) times the SM cross-section is observed (expected) for non-resonant Vhh production when assuming the kinematics are as expected in the SM. Constraints are also placed on Higgs boson coupling modifiers. For the resonant search, upper limits on the production cross-sections are derived for two specific models: one is the production of a vector boson along with a neutral heavy scalar resonance H, in the mass range 260–1000 GeV, that decays into hh, and the other is the production of a heavier neutral pseudoscalar resonance A that decays into a Z boson and H boson, where the A boson mass is 360–800 GeV and the H boson mass is 260–400 GeV. Constraints are also derived in the parameter space of two-Higgs-doublet models.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Exclusive four pion photoproduction in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV
The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. The measurement of coherently photoproduced π + π − π + π − final states in ultraperipheral Pb–Pb collisions at √s NN = 5.02 TeV is presented for the first time. The cross section, dσ/dy, times the branching ratio (ρ →π + π + π − π − ) is found to be 47.8±2.3 (stat.)± 7.7 (syst.) mb in the rapidity interval |y| < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance. The production of two interfering resonances, ρ(1450) and ρ(1700), provides a good description of the data. The values of the masses (m) and widths (Γ) of the resonances extracted from the fit are m 1 = 1385±14 (stat.)±3 (syst.) MeV/c 2 , Γ 1 = 431±36 (stat.)±82 (syst.) MeV/c 2 , m 2 = 1663±13 (stat.)±22 (syst.) MeV/c 2 and Γ 2 = 357 ± 31 (stat.)±49 (syst.) MeV/c 2 , respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions.
FOS: Physical sciences↗
Search for resonant and non-resonant Higgs boson pair production in the $b\overline{b}{\tau}^{+}{\tau}^{-}$ decay channel using 13 TeV $pp$ collision data from the ATLAS detector
A search for Higgs boson pair production in events with two $b$-jets and two $τ$-leptons is presented, using a proton–proton collision dataset with an integrated luminosity of 139 fb -1 collected at $\sqrt{s}$ = 13 TeV by the ATLAS experiment at the LHC. Higgs boson pairs produced non-resonantly or in the decay of a narrow scalar resonance in the mass range from 251 to 1600 GeV are targeted. Events in which at least one $τ$-lepton decays hadronically are considered, and multivariate discriminants are used to reject the backgrounds. No significant excess of events above the expected background is observed in the non-resonant search. The largest excess in the resonant search is observed at a resonance mass of 1 TeV, with a local (global) significance of 3.1$σ$ (2.0$σ$). Observed (expected) 95% confidence-level upper limits are set on the non-resonant Higgs boson pair-production cross-section at 4.7 (3.9) times the Standard Model prediction, assuming Standard Model kinematics, and on the resonant Higgs boson pair-production cross-section at between 21 and 900 fb (12 and 840 fb), depending on the mass of the narrow scalar resonance.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Multiplicity dependence of K*(892) ± production in pp collisions at $\sqrt{s}$ = 13 TeV
The first results of K*(892) ± production at midrapidity (|y| < 0.5) in pp collisions at $\sqrt{s}$= 13 TeV as a function of the event multiplicity are presented. The K*(892) ± has been reconstructed via its hadronic decay channel K*(892) ± → π ± + K$^0_{\textrm{S}}$ using the ALICE detector at the LHC. For each multiplicity class, the differential transverse momentum (p T ) spectrum, the mean transverse momentum ⟨p T ⟩, the p T -integrated yield (dN/dy), and the ratio of the K*(892) ± to K$^0_{\textrm{S}}$ yields are reported. These are consistent with previous K*(892) 0 resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. For the first time, a significant K*(892) ± /K$^0_{\textrm{S}}$ suppression in pp collisions is observed at a 7σ level passing from low to high multiplicity events. The ratios of the p T -differential yields of K*(892) ± and K$^0_{\textrm{S}}$ in high and low multiplicity events are also presented along with their double ratio. For p T ≲ 2 GeV/c this double ratio persists below unity by more than 3σ suggesting that the suppression affects mainly low p T resonances. The measured decreasing trend of the K*(892) ± /K$^0_{\textrm{S}}$ ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.
Hadronic resonance production↗
Combination of Searches for Resonant Higgs Boson Pair Production Using p p Collisions at s = 13 TeV with the ATLAS Detector
A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb − 1 of p p collision data at s = 13 TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: b b ¯ b b ¯ , b b ¯ τ + τ − , and b b ¯ γ γ . 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 2024 CERN
Aad, G. (ORCID:0000000266654934)↗
Certification testing of production superconducting quarter-wave and half-wave resonators for $\mathrm{FRIB}$
We report the Facility for Rare Isotope Beams (FRIB) is designed to accelerate ion beams to 200 MeV per nucleon with 46 superconducting radio-frequency cryomodules. The FRIB driver linac uses quarter-wave resonators and half-wave resonators; with a total of 324 resonators, the linac is currently the largest heavy ion accelerator in the world. Production of jacketed resonators began in January 2014 and was completed in December 2019. Dewar certification testing of all the cavities was done before they were installed into cryomodules. The experience and lessons from more than 5 years of FRIB resonator production and certification testing are analyzed and summarized in this paper.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Bulk properties of the system formed in Au + Au collisions at s N N = 14.5 GeV at the BNL STAR detector
We report systematic measurements of bulk properties of the system created in Au+Au collisions at √ S NN = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum spectra of π ± , K ± and p(p¯) are studied at mid-rapidity (|y| < 0.1) for nine centrality intervals. The centrality, transverse momentum (p T ), and pseudorapidity (η) 3 dependence of inclusive charged particle elliptic flow (v 2 ), and rapidity-odd charged particles directed flow (v 1 ) results near mid-rapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at √ S NN =2.76 TeV. The results at √ S NN = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. Furthermore, these results are important as the 14.5 GeV energy fills the gap in μ B, which is of the order of 100 MeV, between √ S NN =11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Shallow-and-Deep Inelastic Scattering with Neutrinos
In ν/ν-Nucleon/Nucleus interactions Shallow Inelastic Scattering (SIS) is technically defined interms of the four-momentum transfer to the hadronic system as non-resonant meson productionwith predominantly lower Q 2 . This non-resonant meson production intermixes with resonantmeson production in a regime of similar effective hadronic mass W of the interaction. As Q 2 grows non-resonant interactions begin to take place with quarks within the nucleon indicating thestart of Deep Inelastic Scattering (DIS). To essentially separate this resonant plus non-resonantmeson production from DIS quark-fragmented meson production, a cut of 2 GeV in W of theinteractions is generally introduced. However, since experimentally mesons from resonance decaycannot be separated from non-resonant produced mesons, SIS for all practical purposes is definedas inclusive meson production that includes non-resonant plus resonant meson production andthe interference between them. NOTE, this is a mildly modified introduction and overview takenfrom the detailed summary of this topic referenced in the introduction.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
First Measurement of Λ c Baryon Production in Au + Au Collisions at s N N = 200 GeV
Herein we report on the first measurement of the charmed baryon Λ c ± production at midrapidity ( | y | < 1 ) in Au + Au collisions at s NN = 200 GeV collected by the STAR experiment at the Relativistic Heavy Ion Collider. The Λ c / D 0 [denoting ( Λ c + + Λ c - ) / ( D 0 + D ¯ 0 ) ] yield ratio is measured to be 1.08 ± 0.16 ( stat ) ± 0.26 ( sys ) in the 0%–20% most central Au + Au collisions for the transverse momentum ( p T ) range 3 < p T < 6 GeV / c . This is significantly larger than the pythia model calculations for p + p collisions. The measured Λ c / D 0 ratio, as a function of p T and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au + Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λ c / D 0 ratio.
13000 GeV-cms/nucleon↗
Observation of a pseudoscalar excess at the top quark pair production threshold
A search for resonances in top quark pair ($t\overline{t}$) production in final states with two charged leptons and multiple jets is presented, based on proton–proton collision data collected by the CMS experiment at the CERN LHC at $\sqrt{s}$ = 13 TeV , corresponding to 138 fb −1 . The analysis explores the invariant mass of the $t\overline{t}$ system and two angular observables that provide direct access to the correlation of top quark and antiquark spins. A significant excess of events is observed near the kinematic $t\overline{t}$ threshold compared to the non-resonant production predicted by fixed-order perturbative quantum chromodynamics (pQCD). The observed enhancement is consistent with the production of a color-singlet pseudoscalar ($^1S^{[1]}_{0}$) quasi-bound toponium state, as predicted by non-relativistic quantum chromodynamics. Using a simplified model for $^1S^{[1]}_{0}$ toponium, the cross section of the excess above the pQCD prediction is measured to be $8.8^{+1.2}_{-1.4}$ pb.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Multisystem Bayesian constraints on the transport coefficients of QCD matter
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
$K^{*0}$ production in $\text{Au} \times \text{Au}$ collisions at $\sqrt{s_{NN}} = 7.7$, 11.5, 14.5, 19.6, 27, and 39 GeV from the RHIC beam energy scan
We report the measurement of K *0 meson at midrapidity (|y|< 1.0) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27 and 39 GeV collected by the STAR experiment during the RHIC beam energy scan (BES) program. The transverse momentum spectra, yield, and average transverse momentum of K *0 are presented as functions of collision centrality and beam energy. The K *0 /K yield ratios are presented for different collision centrality intervals and beam energies. The K *0 /K ratio in heavy-ion collisions are observed to be smaller than that in small system collisions (e+e and p+p). The K *0 /K ratio follows a similar centrality dependence to that observed in previous RHIC and LHC measurements. The data favor the scenario of the dominance of hadronic re-scattering over regeneration for K *0 production in the hadronic phase of the medium.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗