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At least 235 records · Page 13

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DOE OSTI2023

Observation of an Excess of Dicharmonium Events in the Four-Muon Final State with the ATLAS Detector

A search is made for potential $cc\bar{c}\bar{c}$ tetraquarks decaying into a pair of charmonium states in the four muon final state using proton-proton collision data at $\sqrt{s}$=13 TeV, corresponding to an integrated luminosity of 140 fb -1 recorded by the ATLAS experiment at LHC. Two decay channels, $J/ψ+J/ψ→4μ$ and $J/ψ+ψ(2S)→4μ$, are studied. Backgrounds are estimated based on a hybrid approach involving Monte Carlo simulations and data-driven methods. Statistically significant excesses with respect to backgrounds dominated by the single parton scattering are seen in the di-J/ψ channel consistent with a narrow resonance at 6.9 GeV and a broader structure at lower mass. A statistically significant excess is also seen in the $J/ψ+ψ$(2S) channel. The fitted masses and decay widths of the structures are reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Fraction of χ c Decays in Prompt J / ψ Production Measured in p Pb Collisions at s NN = 8.16 TeV

The fraction of χ c 1 and χ c 2 decays in the prompt J / ψ yield, F χ c → J / ψ = σ χ c → J / ψ / σ J / ψ , is measured by the LHCb detector in p Pb collisions at s NN = 8.16 TeV . The study covers the forward ( 1.5 < y * < 4.0 ) and backward ( − 5.0 < y * < − 2.5 ) rapidity regions, where y * is the J / ψ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 ± 0.3 and 20.8 ± 0.5 nb − 1 , respectively. The result is presented as a function of the J / ψ transverse momentum p T , J / ψ in the range 1 < p T , J / ψ < 20 GeV / c . The F χ c → J / ψ fraction at forward rapidity is compatible with the LHCb measurement performed in p p collisions at s = 7 TeV , whereas the result at backward rapidity is 2.4 σ larger than in the forward region for 1 < p T , J / ψ < 3 GeV / c . The increase of F χ c → J / ψ at low p T , J / ψ at backward rapidity is compatible with the suppression of the ψ ( 2 S ) contribution to the prompt J / ψ yield. The lack of in-medium dissociation of χ c states observed in this study sets an upper limit of 180 MeV on the free energy available in these p Pb collisions to dissociate or inhibit charmonium state formation. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Modification of χ c 1 ( 3872 ) and ψ ( 2 S ) Production in p Pb Collisions at s NN = 8.16 TeV

The LHCb Collaboration measures production of the exotic hadron χ c 1 ( 3872 ) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ ( 2 S ) suggests that the exotic χ c 1 ( 3872 ) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χ c 1 ( 3872 ) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Strong and Weak C P Tests in Sequential Decays of Polarized Σ 0 Hyperons

The J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 processes and subsequent decays are studied using the world’s largest J / ψ and ψ ( 3686 ) data samples collected with the BESIII detector. The parity-violating decay parameters of the decays Σ 0 → Λ γ and Σ ¯ 0 → Λ ¯ γ , α Σ 0 = − 0.0017 ± 0.0021 ± 0.0018 and α ¯ Σ 0 = 0.0021 ± 0.0020 ± 0.0022 , are measured for the first time. The strong C P symmetry is tested in the decays of the Σ 0 hyperons for the first time by measuring the asymmetry A C P Σ = α Σ 0 + α ¯ Σ 0 = ( 0.4 ± 2.9 ± 1.3 ) × 10 − 3 . The weak C P test is performed in the subsequent decays of their daughter particles Λ and Λ ¯ . Also for the first time, the transverse polarizations of the Σ 0 hyperons in J / ψ and ψ ( 3686 ) decays are observed with opposite directions, and the ratios between the S -wave and D -wave contributions of the J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 decays are obtained. These results are crucial to understand the decay dynamics of the charmonium states and the production mechanism of the Σ 0 − Σ ¯ 0 pairs. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Precise Measurement of the e + e − → D s + D s − Cross Section at Center-of-Mass Energies from Threshold to 4.95 GeV

Using the e + e − collision data collected with the BESIII detector operating at the BEPCII collider, at center-of-mass energies from the threshold to 4.95 GeV, we present precise measurements of the cross section for the process e + e − → D s + D s − using a single-tag method. The resulting cross section line shape exhibits several new structures, thereby offering an input for a future coupled-channel analysis and model tests, which are critical to understand vector charmonium-like states with masses between 4 and 5 GeV. Published by the American Physical Society 2024

Ablikim, M.↗

DOE OSTI2013

Heavy quarkonia: Models and theory

Theoretical approaches in heavy quarkonia physics are reviewed. Anomalies in spectra and decays of recently discovered charmonium and bottomoniumstates are highlighted, and exotic interpretations for these states are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Momentum Dependence of Near-Threshold J/ψ Photoproduction off Nuclei

The photoproduction of J/ψ mesons off nuclei at the energies of 8 and 11 GeV, which are close to the threshold for their production on a free nucleon, is considered on the basis of the first-collisionmodel relying on the nuclear spectral function and including incoherent processes of charmonium production in photon–nucleon collisions. The model takes into account the absorption of final J/ψ mesons, the binding of target nucleons, and their Fermi motion, as well as the effect of the scalar J/ψ–nucleus potential (or the inmedium shift of the J/ψ-meson mass) on these processes. Under various assumptions on the magnitude of this shift, the momentum dependences of various observables, such as the relative transparency of carbon and gold nuclei and the J/ψ-meson yields, are calculated for meson production on these nuclei. The observables in question include the relative transparencies of these nuclei to J/ψ mesons and the absolute and relativemeson yields from them. It is shown that, at the energy of 11 GeV, which is above the threshold, the first observable is virtually independent of the in-medium change in the J/ψ-meson mass. At the same time, it is moderately sensitive to this change at the subthreshold energy of 8 GeV. On the other hand, it is shown that, at these photon energies, the absolute and relative values of the differential cross sections, especially for the the heavy nucleus of {sup 197} Au, in the momentum range of 4–6 GeV/с are highly sensitive to the in-medium change in the J/ψ-meson mass. Therefore, the present calculations can be used to determine the unknown shift of the J/ψ-meson mass in nuclei by means of comparing their results with data expected from experiments in Hall C at the Continuous Electron Beam Accelerator Facility (CEBAF, USA) upgraded to the energy of 12 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Measurement of quarkonium production in proton–lead and proton–proton collisions at $5.02~\mathrm {TeV}$ with the ATLAS detector

The modification of the production of J/ψ, ψ(2S), and Υ(nS) (n=1,2,3) in p+Pb collisions with respect to their production in pp collisions has been studied. The p+Pb and pp datasets used in this paper correspond to integrated luminosities of 28 nb –1 and 25 pb –1 respectively, collected in 2013 and 2015 by the ATLAS detector at the LHC, both at a centre-of-mass energy per nucleon pair of 5.02 TeV. The quarkonium states are reconstructed in the dimuon decay channel. The yields of J/ψ and ψ(2S) are separated into prompt and non-prompt sources. The measured quarkonium differential cross sections are presented as a function of rapidity and transverse momentum, as is the nuclear modification factor, R pPb for J/ψ and Υ(nS). No significant modification of the J/ψ production is observed while Υ(nS) production is found to be suppressed at low transverse momentum in p+Pb collisions relative to pp collisions. In conclusion, the production of excited charmonium and bottomonium states is found to be suppressed relative to that of the ground states in central p+Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Observation of $Ξ_c(2930)^0$ and updated measurement of $B^-→K^-Λ^+_c\bar{Λ}^-_c$ at Belle

Here, we report the first observation of the $Ξ_c(2930)^0$ charmed-strange baryon with a significance greater than 5σ. The $Ξ_c(2930)^0$ is found in its decay to $K^-Λ^+_c$ in $B^-→K^-Λ^+_c\bar{Λ}^-_c$ decays. The measured mass and width are $[2928.9±3.0(stat.)^{+0.9}_{-12.0}(syst.)]$ MeV/ $c^2$ and $[19.5±8.4(stat.)^{+5.9}_{-7.9}(syst.)]$ MeV, respectively, and the product branching fraction is $\mathcal{B}(B^-→Ξ_c(2930)^0\bar{Λ}^-_c)\mathcal{B}(Ξ_c(2930)^0→K^-Λ^+_c)=[1.73±0.45(stat.)±0.21(syst.)]×10^{-4}$. We also measure $\mathcal{B}(B^-→K^-Λ^+_c\bar{Λ}^-_c)=[4.80±0.43(stat.)±0.60(syst.)]×10^{-4}$ with improved precision, and search for the charmonium-like state Y(4660) and its spin partner, Y η , in the $Λ^+_c\bar{Λ}^-_c$ invariant mass spectrum. No clear signals of the Y(4660) nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of (772±11)×10 6 B B ¯ pairs collected at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Evidence of a structure in $\bar{K}^{0} \Lambda _{c}^{+}$ consistent with a charged $\Xi _c(2930)^{+}$, and updated measurement of $\bar{B}^{0} \rightarrow \bar{K}^{0} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$ at Belle

We report evidence for the charged charmed-strange baryon Ξ c (2930) + with a signal significance of 3.9 σ with systematic errors included. The charged Ξ c (2930) + is found in its decay to K$0\atop{S}$Λ$+\atop{c}$ in the substructure of $\bar{B}$ 0 →K$0\atop{S}$Λ$+\atop{c}$ $\bar{Λ}$ $\bar{c}$ decays. The measured mass and width are [2942.3±4.4(stat.)±1.5(syst.)] MeV/c 2 and [14.8±8.8(stat.)±2.5(syst.)] MeV, respectively, and the product branching fraction is B($\bar{B^0}$→Ξ c (2930) + $\bar{Λ}$ $\bar{c}$)B(Ξ c (2930) + →$\bar{K}^0$Λ$+\atop{c}$)=[2.37±0.51(stat.)±0.31(syst.)]×10 -4 . We also measure B($\bar{B}^{0} \rightarrow \bar{K}^{0} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$)=[3.99±0.76(stat.)±0.51(syst.)]×10 -4 with greater precision than previous experiments, and present the results of a search for the charmonium-like state Y(4660) and its spin partner,Y η , in the Λ$+\atop{c}$ $\bar{Λ}$ $-\atop{c}$ invariant mass spectrum. No clear signals of the Y(4660) or Y η are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of (772±11)×10 6 $B\bar{B}$ pairs collected at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Quark structure of the $\chi _{\mathrm{c}}(3P)$ and X(4274) resonances and their strong and radiative decays

We calculate the masses of χc(3P) states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of χc(2P) and χb(3P) multiplets (Ferretti and Santopinto in Phys Lett B 789:550, 2019]. We also compute the open-charm strong decay widths of the χc(3P) states and their radiative transitions. According to our predictions, the χc(3P) states should be dominated by the charmonium core, but they may also show small meson-meson components. The X(4274) is interpreted as a cc¯ χc1(3P) state. More information on the other members of the χc(3P) multiplet, as well as a more rigorous analysis of the X(4274)’s decay modes, are needed to provide further indications on the quark structure of the previous resonance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Light-front wavefunctions of mesons by design

Abstract We develop a mechanism to build the light-front wavefunctions (LFWFs) of meson bound states on a small-sized basis function representation. Unlike in a standard Hamiltonian formalism, the Hamiltonian in this method is implicit, and the information of the system is carried directly by the functional form and adjustable parameters of the LFWFs. In this work, we model the LFWFs for four charmonium states, $$\eta _c$$ η c , $$J/\psi $$ J / ψ , $$\psi '$$ ψ ′ , and $$\psi (3770)$$ ψ ( 3770 ) as superpositions of orthonormal basis functions. We choose the basis functions as eigenfunctions of an effective Hamiltonian, which has a longitudinal confining potential in addition to the transverse confining potential from light-front holographic QCD. We determine the basis function parameters and superposition coefficients by employing both guidance from the nonrelativistic description of the meson states and the experimental measurements of the meson decay widths. With the obtained wavefunctions, we study the features of those meson states, including charge radii and parton distribution functions. We use the $$J/\psi $$ J / ψ LFWF to calculate the meson production in diffractive deep inelastic scattering and ultra-peripheral heavy-ion collisions, and the $$\eta _c$$ η c LFWF to calculate its diphoton transition form factor. Both results show good agreement with experiments. The obtained LFWFs have simple-functional forms and can be readily used to predict additional experimental observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

50 Years of quantum chromodynamics

Quantum Chromodynamics, the theory of quarks and gluons, whose interactions can be described by a local SU(3) gauge symmetry with charges called “color quantum numbers”, is reviewed; the goal of this review is to provide advanced Ph.D. students a comprehensive handbook, helpful for their research. When QCD was “discovered” 50 years ago, the idea that quarks could exist, but not be observed, left most physicists unconvinced. Then, with the discovery of charmonium in 1974 and the explanation of its excited states using the Cornell potential, consisting of the sum of a Coulomb-like attraction and a long range linear confining potential, the theory was suddenly widely accepted. This paradigm shift is now referred to as the November revolution. It had been anticipated by the observation of scaling in deep inelastic scattering, and was followed by the discovery of gluons in three-jet events.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Low energy determination of the QCD strong coupling constant on the lattice

Here we present a determination of the strong coupling constant from lattice QCD using the moments of pseudo-scalar charmonium correlators calculated using highly improved staggerered quark action. We obtain a value α s ( μ = mc) = 0.3397(56), which is the lowest energy determination of the strong coupling constant so far.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2016

Event Patterns Extracted from Transverse Momentum and Rapidity Spectra of Z Bosons and Quarkonium States Produced in pp and Pb-Pb Collisions at LHC

Transverse momentum ( p T ) and rapidity ( y ) spectra of Z bosons and quarkonium states (some charmonium c c ¯ mesons such as J / ψ and ψ ( 2 S ) and some bottomonium b b ¯ mesons such as Υ ( 1 S ) , Υ ( 2 S ) , and Υ ( 3 S ) ) produced in proton-proton (pp) and lead-lead (Pb-Pb) collisions at the large hadron collider (LHC) are uniformly described by a hybrid model of two-component Erlang distribution for p T spectrum and two-component Gaussian distribution for y spectrum. The former distribution results from a multisource thermal model, and the latter one results from the revised Landau hydrodynamic model. The modelling results are in agreement with the experimental data measured in pp collisions at center-of-mass energies s = 2.76 and 7 TeV and in Pb-Pb collisions at center-of-mass energy per nucleon pair s N N = 2.76 TeV. Based on the parameter values extracted from p T and y spectra, the event patterns (particle scatter plots) in two-dimensional p T - y space and in three-dimensional velocity space are obtained.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Measurement of the production cross section of prompt J / ψ mesons in association with a W ± boson in p p collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. The process P P --> W J/PSI X provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb^-1 of sqrt(s) = 7 TeV pp collisions at the LHC, the first observation is made of the production of W + prompt J/psi events in hadronic collisions, using W --> MU NU and J/PSI --> MU MU. A yield of 27.4 +7.5,-6.5 W + prompt J/psi events is observed, with a statistical significance of 5.1 sigma. The production rate as a ratio to the inclusive W boson production rate is measured, and the double parton scattering contribution to the cross section is estimated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Measurement of χ c 1 and χ c 2 production with s = 7 TeV p p collisions at ATLAS

CERN-LHC. The prompt and non-prompt production cross-sections for the chi_c1 and chi_c2 charmonium states are measured in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the LHC using 4.5 fb-1 of integrated luminosity. The chi_c states are reconstructed through the radiative decay chi_c --> J/psi + gamma (with J/psi --> mu+ mu-) where photons are reconstructed from gamma --> e+ e- conversions. The differential cross sections for both prompt and non-prompt production of the chi_c1 and chi_c2 states are measured as a function of both J/psi and chi_c pT. The fraction of prompt J/psi produced in feed-down from radiative chi_c decays is also measured in addition to the production rate of chi_c2 relative to chi_c1, for both prompt and non-prompt chi_c production. The measurements have not been corrected for the chi_c --> J/psi + gamma and J/psi --> mu+ mu- branching fractions. All measurements are made within the fiducial region ABS(YRAP(J/PSI)) < 0.75.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Measurement of differential J / ψ production cross-sections and forward-backward ratio in p+Pb collisions with the ATLAS detector

CERN-LHC. Measurements of differential cross-sections for J/psi production in p+Pb collisions at sqrt(s_NN) = 5.02 TeV at the LHC with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb^-1. The J/psi mesons are reconstructed in the dimuon decay channel over the transverse momentum range 8< pT< 30 GeV and over the center-of-mass rapidity range -2.87< y* <1.94. Prompt J/psi are separated from J/psi resulting from b-hadron decays through an analysis of the distance between the J/psi decay vertex and the event primary vertex. The differential cross-section for production of nonprompt J/psi is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results constrain the kinematic dependence of nuclear modifications of charmonium and b-quark production in p+Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗