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At least 127 records · Page 7
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DOE OSTI2025

Shining a Light on the Nucleus: Photonuclear Measurements from Correlations to Charmonium

The atomic nucleus is comprised of a collection of nucleons (protons and neutrons), which are bound together by the nucleon-nucleon (NN) interaction that originates from Quantum Chromodynamics (QCD). While most nucleons experience the force from the rest of the nu- cleus as a single net “mean-field” interaction that binds them relatively weakly, a small but impactful fraction are in configurations called “Short-Range Correlations” (SRCs), in which they pair with another nucleon at very short distance to experience strong interactions, sig- nificant binding, and high momentum. Hard, high-energy scattering reactions in which an SRC pair is broken apart, knocking both nucleons out of the nucleus, provide the ability to probe the details of these SRC configurations in the nucleus. Previous measurements have had limited statistics and kinematic reach, and the theoretical tools available were in- sufficient to draw quantitative conclusions regarding the ground-state properties of SRCs. The studies described in this thesis represent the first global analysis of SRC breakup mea- surements in order to present a unified picture of SRCs within light- to medium-size nuclei. This includes the use of a novel theoretical framework, the Generalized Contact Formalism, which connects scattering cross-section measurements and the ground-state properties of the SRC pair, to quantitatively interpret a variety of electron-scattering measurements. This is brought to culmination by a report on the first measurement of SRC pairs via the use of hard meson photoproduction reactions, which, despite differing significantly from the me- chanics of electron-scattering, is well-described under a common framework, pointing to a consistent and universal picture of SRCs across reaction channels. I also report on the first measurement of J/¿ photoproduction in the near- and below-threshold kinematic region, giving the first insights to the gluonic structure of bound nucleons in the large-x “valence” region and providing constraints on a gluonic “EMC effect”. In addition to these studies, I provide details on the search for Primakoff production of axion-like particles using the pho- toproduction data taken for this experiment, and I conclude by describing studies of nucleon spin structure measurements that will be performed at the forthcoming U.S. Electron-Ion Collider.

Pybus, Jackson↗
DOE OSTI2011

Quarkonium Spectroscopy And Search for New States at BaBar

The BaBar experiment at the PEP-II B-factory gives excellent opportunities for the quarkonium spectroscopy. Investigation of the properties of new states like the X(3872), Y(3940) and Y(4260) are performed aiming to understand their nature. Recent BaBar results will be presented in this paper. At the B-factories charmonium and charmonium-like states are copiously produced via several mechanisms: in B decay (color suppressed b {yields} c transition), double charmonium production (e{sup +}e{sup -} {yields} c{bar c} + c{bar c}), two photons production ({gamma}*{gamma}* {yields} c{bar c}, where the c{bar c} state has positive C-parity) and in initial state radiation (ISR) when the e{sup {+-}} in its initial state emits a photon lowering the effective center of mass energy of the e{sup +}e{sup -} interaction (e{sup +}e{sup -} {yields} {gamma}{sub ISR} + c{bar c}, where the charmonium state has the quantum numbers J{sup PC} = 1{sup -2}). Many new states have been recently discovered at the B-factories, BaBar and Belle, above the D{bar D} threshold in the charmonium energy region. While some of them appear to be consistent with conventional c{sub c} states others do not fit with any expectation. Several interpretations for these states have been proposed: for some of them the mass values suggest that they could be conventional charmonia, but also other interpretations like D{sup 0}{bar D}*{sup 0} molecule or diquark-antidiquark states among many other models have been advanced. Reviews can be found in Refs. [1][2]. In all cases the picture is not completely clear. This situation could be remedied by a coherent search of the decay pattern to D{bar D}, search for production in two-photon fusion and ISR, and of course improving the statistical precision upon the current measurements. The BaBar experiment at the PEP-II asymmetric collider, designed to perform precision measurement of CP violation in the B meson system, has an extensive quarkonium spectroscopy program. Recent BaBar outcomes on the X(3872) and Y(4260) and a new result on the Y(3940) are reported here.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Energy dependence of forward-rapidity $\mathrm {J}/\psi $ and $\psi \mathrm {(2S)}$ production in pp collisions at the LHC

We present results on transverse momentum (p T ) and rapidity (y) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/ψ and ψ(2S) at forward rapidity (2.5 < y < 4) as well as ψ(2S)-to-J/ψ cross section ratios. These quantities are measured in pp collisions at center of mass energies √s = 5.02 and 13 TeV with the ALICE detector. Both charmonium states are reconstructed in the dimuon decay channel, using the muon spectrometer. A comprehensive comparison to inclusive charmonium cross sections measured at √s = 2.76, 7 and 8 TeV is performed. A comparison to non-relativistic quantum chromodynamics and fixed-order next-to-leading logarithm calculations, which describe prompt and non-prompt charmonium production respectively, is also presented. A good description of the data is obtained over the full p T range, provided that both contributions are summed. In particular, it is found that for p T > 15 GeV/c the non-prompt contribution reaches up to 50% of the total charmonium yield.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Recent Results from CLEO

The CLEO Experiment, utilizing symmetric e{sup +}e{sup -} collisions provided by the Cornell Electron Storage Ring (CESR) in the charmonium and bottomonium regions, has a wide-reaching program in the study of hadrons and the strong force. This review briefly summarizes recent contributions the CLEO Collaboration has made in the study of: (1) light quark systems (rare decays of the {eta}'); (2) charmonium radiative decays to light quarks (J/{psi} and {psi}(2S) radiative decays to the {eta} and {eta}'); (3) mesons with open charm (the D and D{sub s} decay constants); (4) charmonium transitions (a multipole analysis of {psi}(2S) {yields} {gamma}{chi}{sub c1,2} and {chi}{sub c1,2} {yields} {gamma}J/{psi}); and (5) bottomonium spectroscopy (confirming evidence for the discovery of the {eta}{sub b}(1S)).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Heavy quarkonia production at energies available at the CERN Large Hadron Collider and future electron-ion colliding facilities using basis light-front quantization wave functions

We study here exclusive charmonium and bottomonium production in ultraperipheral heavy-ion collisions and electron-ion collisions within the dipole picture. We employ heavy quarkonium light-front wave functions obtained within the basis light-front quantization framework, which has some features of the light-front holographic QCD. We focus on comparison with measurements of exclusive charmonium and bottomonium production in ultraperipheral pp, pPb, and PbPb collisions at the CERN Large Hadron Collider and find reasonable agreement with the cross sections. We also discuss the coherent production cross-section ratios of excited states to the ground state for charmonium and bottomonium, which exhibit insensitivity to the dipole model parameters. We demonstrate that electron-ion collisions provide an opportunity for a quantitative study of heavy quarkonium structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Near-threshold J/ψ-meson photoproduction on nuclei

On the basis of the first-collision model that relies on the nuclear spectral function and which includes incoherent processes involving charmonium production in proton–nucleon collisions, the photoproduction of J/ψ mesons on nuclei is considered at energies close to the threshold for their production on a nucleon. The absorption of final J/ψ mesons, their formation length, and the binding and Fermi motion of target nucleons are taken into account in this model along with the effect of the nuclear potential on these processes. The A dependences of the absolute and relative charmonium yields are calculated together with absolute and relative excitation functions under various assumptions on the magnitude of the cross section for J/ψN absorption, the J/ψ-meson formation length, and their inmedium modification. It is shown that, at energies above the threshold, these features are virtually independent of the formation length and the change in the J/ψ-meson mass in nuclear matter but are rather highly sensitive to the cross section for J/ψN interaction. The calculations performed in the present study can be used to determine the unknown cross section for J/ψ-meson absorption in nuclei from a comparison of their results with data expected from experiments in the Hall C of the CEBAF (USA) facility upgraded to the energy of 12 GeV. It is also shown that the absolute and relative excitation functions for J/ψ mesons in photon–nucleus reactions at subthreshold energies are sensitive to the change in the meson mass and, hence, carry information about the properties of charmonium in nuclear matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Quarkonium States at B-Factories

An overview is given on recent progress in the study of quarkonium spectroscopy at the B-factories. In particular, an updated status report is presented of the long list of 'charmonium-like' resonances newly discovered, whose assignment as true charmonium states is in most cases at least controversial. Also, new measurements on the decay properties of bottomonium states above open-B production thresholds are shown. Much of the progress attained in recent years in the study of the quarkonium spectra is owed to the measurements performed at B-factories. The impressive amount of data recorded by the BABAR and Belle experiments has made it possible to study rare decay chains and to look for as yet undiscovered resonances in the charmonium and bottomonium mass regions. Results presented here are based on different subsamples of the full datasets recorded up to now by the two experiments, corresponding to integrated luminosities of about 430 fb{sup -1}(BABAR - final) and about 850 fb{sup -1}(Belle). Significant contributions also come from the analysis of the various data samples recorded by the CLEO detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Centrality dependence of J /ψ and ψ (2S) production and nuclear modification in p-Pb collisions at \( \sqrt{s_{\mathrm{NN}}} \) = 8 . 16 TeV

The inclusive production of the J/ ψ and ψ (2S) charmonium states is studied as a function of centrality in p-Pb collisions at a centre-of-mass energy per nucleon pair \( \sqrt{s_{\mathrm{NN}}} \) = 8 . 16 TeV at the LHC. The measurement is performed in the dimuon decay channel with the ALICE apparatus in the centre-of-mass rapidity intervals – 4 . 46 < y cms < – 2 . 96 (Pb-going direction) and 2 . 03 < y cms < 3 . 53 (p-going direction), down to zero transverse momentum ( p T ). The J/ ψ and ψ (2S) production cross sections are evaluated as a function of the collision centrality, estimated through the energy deposited in the zero degree calorimeter located in the Pb-going direction. The p T -differential J/ ψ production cross section is measured at backward and forward rapidity for several centrality classes, together with the corresponding average \( \left\langle {p}_{\mathrm{T}}\right\rangle \) and \( \left\langle {p}_{\mathrm{T}}^2\right\rangle \) values. The nuclear effects affecting the production of both charmonium states are studied using the nuclear modification factor. In the p-going direction, a suppression of the production of both charmonium states is observed, which seems to increase from peripheral to central collisions. In the Pb-going direction, however, the centrality dependence is different for the two states: the nuclear modification factor of the J/ ψ increases from below unity in peripheral collisions to above unity in central collisions, while for the ψ (2S) it stays below or consistent with unity for all centralities with no significant centrality dependence. The results are compared with measurements in p-Pb collisions at \( \sqrt{s_{\mathrm{NN}}} \) = 5 . 02 TeV and no significant dependence on the energy of the collision is observed. Finally, the results are compared with theoretical models implementing various nuclear matter effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Centrality dependence of ψ(2S) suppression in p-Pb collisions at s N N = 5.02 $$ {\sqrt{s}}_{\mathrm{NN}}=5.02 $$ TeV

The inclusive production of the ψ(2S) charmonium state was studied as a function of centrality in p-Pb collisions at the nucleon-nucleon center of mass energy √ s NN = 5.02 TeV at the CERN LHC. The measurement was performed with the ALICE detector in the center of mass rapidity ranges -4.46 < y cms < -2.96 and 2.03 < y cms < 3.53, down to zero transverse momentum, by reconstructing the ψ(2S) decay to a muon pair. The ψ(2S) production cross section σ ψ(2S) is presented as a function of the collision centrality, which is estimated through the energy deposited in forward rapidity calorimeters. The relative strength of nuclear effects on the ψ(2S) and on the corresponding 1S charmonium state J/ψ is then studied by means of the double ratio of cross sections [σ ψ(2S) /σ J/ψ ] pPb /[σ ψ (2S) /σ J/ψ ] pp between p-Pb and pp collisions, and by the values of the nuclear modification factors for the two charmonium states. The results show a large suppression of ψ(2S) production relative to the J/ψ at backward (negative) rapidity, corresponding to the flight direction of the Pb-nucleus, while at forward (positive) rapidity the suppressions of the two states are comparable. Finally, comparisons to results from lower energy experiments and to available theoretical models are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Heavy quark diffusion from lattice QCD spectral functions

We analyze the low-frequency part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region 1.5 ≲ T/T c ≲ 3 as well as for T ≅ 0.75T c . We present evidence for the existence of a transport peak above T c and its absence below Tc. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation we also determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗