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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

On the question of quark confinement in the Abelian U(1) QED gauge interaction

If we approximate light quarks as massless and apply the Schwinger confinement mechanism to light quarks, we will reach the conclusion that a light quark q and its antiquark ${\bar q}$ will be confined as a $q\bar q$ boson in the Abelian U(1) QED gauge interaction in (1+1)D, as in an open string. From the work of Coleman, Jackiw, and Susskind, we can infer further that the Schwinger confinement mechanism persists even for massive quarks in (1+ 1)D. Could such a QED-confined $q\bar q$ one-dimensional open string in (1 + 1) D be the idealization of a flux tube in the physical world in (3+l)D, similar to the case of QCD-confined $q\bar q$ open string? If so, the QED-confined $q\bar q$ bosons may show up as neutral QED mesons in the mass region of many tens of MeV [Phys. Rev. C 81, 064903 (2010) & J. High Energy Phys. 2020(8), 165 (2020)]. Is it ever possible that a quark and an antiquark be produced and interact in QED alone to form a confined QED meson? Is there any experimental evidence for the existence of a QED meson (or QED mesons)? The observations of the anomalous soft photons, the XI7 particle, and the E38 particle suggest that they may bear the experimental evidence for the existence of such QED mesons. Further confirmation and investigations on the XI7 and E38 particles will shed definitive light on the question of quark confinement in QED in (3+1)D. Finally, implications of quark confinement in the QED interaction are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Coherent J/ψ photoproduction at midrapidity in Pb – Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The coherent J∕𝜓 photoproduction cross section is measured for the first time at midrapidity in peripheral to semicentral P b − P b collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The centrality differential cross section d 𝜎 ∕d𝑦 is reported for the centrality range 40–90%, together with the doubly-differential cross section d 2 𝜎∕d𝑦d𝑝 T , extracted in two peripheral centrality classes. The J∕𝜓 mesons are reconstructed in the dielectron channel, in the rapidity interval |𝑦| < 0.9 using the ALICE central barrel detectors. The J∕𝜓 cross section at midrapidity is statistically compatible to the earlier ALICE measurement at forward rapidity and at the same centre-of-mass energy, and shows only a mild centrality dependence over the covered range. Several sets of theoretical calculations taking into account the hadronic overlap in the collisions but ignoring possible final-state effects from a hot expanding medium are found to give a fairly good description of the current measurements within uncertainties.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei

Strong interactions preserve an approximate isospin symmetry between up (u) and down (d) quarks, part of the more general flavor symmetry. In the case of K meson production, if this isospin symmetry were exact, it would result in equal numbers of charged (K + and K − ) and neutral (K 0 and ${\overline{K}}^{0}$) mesons produced in collisions of isospin-symmetric atomic nuclei. Here, we report results on the relative abundance of charged over neutral K meson production in argon and scandium nuclei collisions at a center-of-mass energy of 11.9 GeV per nucleon pair. We find that the production of K + and K − mesons at mid-rapidity is (18.4 ± 6.1)% higher than that of the neutral K mesons. Although with large uncertainties, earlier data on nucleus-nucleus collisions in the collision center-of-mass energy range $2.6 \, < \, \sqrt{{s}_{NN}} \, < \, 200$ GeV are consistent with the present result. Using well-established models for hadron production, we demonstrate that known isospin-symmetry breaking effects and the initial nuclei containing more neutrons than protons lead only to a small (few percent) deviation of the charged-to-neutral kaon ratio from unity at high energies. Thus, they cannot explain the measurements. The significance of the flavor-symmetry violation beyond the known effects is 4.7σ when the compilation of world data with uncertainties quoted by the experiments is used. New systematic, high-precision measurements and theoretical efforts are needed to establish the origin of the observed large isospin-symmetry breaking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for $D^{*}(2007)^{0} \rightarrow \mu ^{+} \mu ^{-}$ in $B^{-}\rightarrow \pi ^{-} \mu ^{+} \mu ^{-}$ decays

The very rare D* (2007) 0 → μ + μ – decay is searched for by analysing B – → μ + μ – decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb –1 . The signal signature corresponds to simultaneous peaks in the μ + μ – and π – μ + μ – invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at B (D* (2007) 0 → μ + μ – ) < 2.6 x 10 –8 at 90% confidence level. This is the first limit on the branching fraction of D* (2007) 0 → μ + μ – decays and the most stringent limit on D* (2007) 0 decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The GLUEX DIRC program

The GLUEX experiment is located in experimental Hall D at Jefferson Lab (JLab) and provides a unique capability to search for hybrid mesons in high-energy photoproduction, utilizing a ~9 GeV linearly polarized photon beam. The initial, low-intensity phase of GLUEX was recently completed and a high-intensity phase has begun in 2020 which includes an upgraded kaon identification system, known as the DIRC (Detection of Internally Reflected Cherenkov light), utilizing components from the decommissioned BaBar DIRC. The identification of kaon final states will significantly enhance the GLUEX physics program, to aid in inferring the quark flavor content of conventional (and potentially hybrid) mesons. Here, we describe the installation of the GLUEX DIRC and the analysis of initial commissioning data.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Status and Performance of the GlueX DIRC

The GlueX experiment is located in experimental Hall D at Jefferson Lab (JLab) and provides a unique capability to search for hybrid mesons in high-energy photoproduction, utilizing a $\sim$9 GeV linearly polarized photon beam. Since 2020 a Detector of Internally Reflected Cherenkov light (DIRC) has been in use at GlueX, utilizing components from the decommissioned BaBar DIRC. In this contribution we will discuss the status and performance of the GlueX DIRC with the data collected to date, including recent developments in the use of machine learning for particle identification.

Stevens, Justin [College of William and Mary, Will↗
DOE OSTI2022

Probing the Gluonic Structure of the Deuteron with J / ψ Photoproduction in d + Au Ultraperipheral Collisions

Understanding gluon density distributions and how they are modified in nuclei are among the most important goals in nuclear physics. In recent years, diffractive vector meson production measured in ultraperipheral collisions (UPCs) at heavy-ion colliders has provided a new tool for probing the gluon density. In this Letter, we report the first measurement of J/psi photoproduction off the deuteron in UPCs at the center-of-mass energy root √S-NN = 200 GeV in d + Au collisions. The differential cross section as a function of momentum transfer -t is measured. In addition, data with a neutron tagged in the deuteron-going zero-degree calorimeter is investigated for the first time, which is found to be consistent with the expectation of incoherent diffractive scattering at low momentum transfer. Theoretical predictions based on the color glass condensate saturation model and the leading twist approximation nuclear shadowing model are compared with the data quantitatively. A better agreement with the saturation model has been observed. With the current measurement, the results are found to be directly sensitive to the gluon density distribution of the deuteron and the deuteron breakup process, which provides insights into the nuclear gluonic structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Charmonium χ c 0 and χ c 2 resonances in coupled-channel scattering from lattice QCD

In order to explore the spectrum of hidden-charm scalar and tensor resonances, we study meson-meson scattering with J P C = 0 + + , 2 + + in the charmonium energy region using lattice QCD. Employing a light-quark mass corresponding to m π ≈ 391 MeV , we determine coupled-channel scattering amplitudes up to around 4100 MeV considering all kinematically relevant channels consisting of a pair of open-charm mesons or a charmonium meson with a light meson. A single isolated scalar resonance near 4000 MeV is found with large couplings to D D ¯ , D s D ¯ s and the kinematically closed D * D ¯ * channel. A single tensor resonance at a similar mass couples strongly to D D ¯ , D D ¯ * and D * D ¯ * . We compare the extracted resonances to contemporary experimental candidate states, previous lattice results and theoretical modeling. In contrast to several other studies, we do not find any significant feature in the scalar amplitudes between the ground state χ c 0 ( 1 P ) and the resonance found around 4000 MeV. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Structure of open-flavor four-quark states in the charm and bottom region

We present quantitative results for masses and the internal structure of four-quark states with two heavy quarks, i.e., Q Q ′ q ¯ q ¯ ′ with Q , Q ′ ∈ { c , b } and q , q ′ ∈ { u , d , s } , and J P ∈ 1 + . The composition of these states in terms of meson-meson and diquark-antidiquark pairs, extracted from a relativistic four-body Faddeev-Yakubowski equation, is dynamically determined from underlying QCD forces. We find states at energy levels in very good agreement with lattice QCD and, where available, with experimental states. Their internal structure, most notably between the T c c + , T b c and T b b − , show significant and sizeable variations. Published by the American Physical Society 2025

Hoffer, Joshua (ORCID:0009000871793956)↗
DOE OSTI2022

The Jefferson Lab Eta Factory (JEF) experiment

The Jefferson Lab Eta Factory (JEF) experiment is an upcoming experiment designed to run in Hall D at Jefferson Lab using an upgraded GlueX spectrometer to study various decays of the ? meson. The GlueX spectrometer consists of a ?2 Tesla solenoid magnet housing a liquid hydrogen target and drift chambers used for tracking charged particles and an array of lead glass blocks (the Forward Calorimeter (FCAL)) downstream of the magnet for detecting neutral particles. The decays of the ? meson can be used to measure the light quark mass ratio via the ???+???0 channel and allow access to higher-order terms in Chiral Perturbation Theory via the ???0?? channel. The decays can also be used to constrain new charge-conjugation violating/parity conserving (CVPC) reactions and to search for signatures of dark matter. In particular, the ???0?? channel can be used to search for lepto-phobic dark vector (B) bosons in the reaction ??B? (B??0?) or dark scalar (S) bosons in the reaction ???0S (S???). Studying the rare radiative decay channel ???0?? requires replacing the 4×4×45 cm3 lead glass blocks in the inner region of the FCAL with 2×2×20 cm3 lead tungstate crystals, which will provide twice better position and energy resolution. This talk will describe the JEF physics program and the upgrade to the FCAL.

Taylor, Simon↗
DOE OSTI2025

New insights into the doubly charmed exotic mesons

Abstract Using effective Lagrangians constrained by the heavy quark spin symmetry and chiral symmetry, for the light quarks, we analyze the $$D^0 D^0\pi ^+,$$ D 0 D 0 π + , $$\bar{D}^0D^0\pi ^0$$ D ¯ 0 D 0 π 0 and $$D^0\bar{D}^{*0}$$ D 0 D ¯ ∗ 0 invariant mass spectra. Performing a simultaneous analysis of the doubly charmed and charm-anti-charm states gives further insights into the nature of the $$T^+_{cc}$$ T cc + and $$\chi ^0_{c1}(3872),$$ χ c 1 0 ( 3872 ) , exotic hadrons. It is confirmed that both states should lie below their respective $$DD^*$$ D D ∗ / $$D\bar{D}^*$$ D D ¯ ∗ thresholds. Also, the contributions of the triangle and box diagrams are negligible.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

New state of matter between the hadronic phase and the quark-gluon plasma?

Lattice-quantum chromodynamics (QCD) simulations and theoretical arguments hint at the existence of an intermediate phase of strongly interacting matter between a confined hadron gas and a deconfined quark-gluon plasma (QGP). We qualitatively and semiquantitatively explore and differentiate the phase structures in the temperature window from the QCD pseudocritical temperature 𝑇 c ≃ 160 MeV to the pure gluonic deconfinement temperature 𝑇 d ≃ 285 MeV. We propose a three-regime picture using a hadron resonance gas description augmented with the exponential spectrum of strings, corresponding to highly excited mesons and glueballs, based on the analysis of a large number 𝑁 c of colors. We estimate the entropy density from our model to confirm that the lattice-QCD data are bracketed with three regimes, i.e., a hadron gas, a QGP, and a new phase for 𝑇 c ≲ 𝑇 ≲ 𝑇 d . In this new phase, which we name a spaghetti of quarks with glueballs (SQGBs), thermal degrees of freedom of quarks are liberated, yet gluons remain confined in glueballs. Since the Hagedorn temperature 𝑇 H ∼ 285 MeV is universal in the meson and the glueball sectors, in the infinite-𝑁 c limit, the phase diagram in the plane of the baryon chemical potential and the temperature is reduced to one with the confined and deconfined phases and quarkyonic matter at high density. At large but finite 𝑁 c , an SQGB window may open between these phases. We point out that the SQGB has interesting similarities with quarkyonic matter and that this matter in the large-𝑁 c limit is confined as measured by the interaction between heavy quarks, but behaves in other respects like a quasifree gas of quarks. As a result of the extrapolation to 𝑁 c = 3, we present a revised phase diagram with the SQGB phase bounded by thermal crossovers. Finally, we give a quantitative analysis of chiral-symmetry restoration in the SQGB phase.

Color confinement↗
DOE OSTI2024

A Measurement of the Eta Meson Radiative Decay Width via the Primakoff Effect

The ? meson is an interesting tool to study fundamental symmetries in Quantum Chromodynamics (QCD). In particular, its radiative decay width, ? p? Ñ ??q, is an important quantity that can be predicted in the framework of Chiral Perturbation Theory. A precision measurement of this quantity would provide critical inputs to understanding the mixing of the ? and ?1 mesons and extracting constants with wide-ranging applications in low-energy QCD. This decay width has been measured in the past using two different experimental techniques. The more popular technique utilized e`e´ collisions to produce ? mesons through electromagnetic interactions. Today, the Particle Data Group (PDG) averages the results of five such experiments to obtain their currently-accepted value of the decay width as: 0.515?0.018 keV. However the first measurement of this quantity was obtained from a fixed-target experiment that measured the cross section for photoproduction of ? mesons on a nuclear target via the Primakoff effect. Their result of 0.324?0.046 keV shows strong tension with the average of the collider measurements, motivating a new, high precision measurement using the Primakoff method. For this purpose, the PrimEx-eta experiment was conducted in Hall D of the Thomas Jefferson National Accelerator Facility (Jefferson Lab or JLab). The data is currently being analyzed to measure the differential cross section for the photoproduction of ? mesons on a liquid, 4He target. Preliminary results obtained from the analysis of the first phase of the PrimEx-eta experiment show reasonable agreement with the currently-accepted PDG value of the radiative decay width. However, as will be discussed, there are many challenges to this precision measurement which must be studied before any results can be finalized and compared with previous measurements. In parallel to the ? decay width measurement, the PrimEx-eta experiment measured the total cross section for the fundamental, Quantum Electrodynamics (QED) process of Compton scattering from the atomic electrons inside the target. The results obtained from this measurement are in strong agreement with the next-to-leading order QED calculations, and the total combined uncertainties are below 3% for incident photon energies between 7-10 GeV. In addition to providing the first precision measurement of the total Compton scattering cross section within this beam energy range, this measurement verifies the capability of the PrimEx-eta experimental setup to perform absolute cross section measurements at forward angles, and serves as a reference process for the calibration of systematic uncertainties.

Smith, Andrew↗
DOE OSTI2024

Multiplicity dependence of ϒ production at forward rapidity in pp collisions at $\sqrt{s}$ = 13 TeV

The measurement of ϒ(1S), ϒ(2S), and ϒ(3S) yields as a function of the charged-particle multiplicity density, d N ch /d η , using the ALICE experiment at the LHC, is reported in pp collisions at √s = 13 TeV. The Υ meson yields are measured at forward rapidity (2.5 < y < 4) in the dimuon decay channel, whereas the charged-particle multiplicity is defined at central rapidity (| η | <1). Both quantities are divided by their average value in minimum bias events to compute the self-normalized quantities. The increase of the self-normalized ϒ(1S), ϒ(2S), and ϒ(3S) yields is found to be compatible with a linear scaling with the self-normalized d N ch /d η , within the uncertainties. The self-normalized yield ratios of excited-to-ground ϒ states are compatible with unity within uncertainties. Similarly, the measured double ratio of the self-normalized ϒ(1S) to the self-normalized J/ ψ yields, both measured at forward rapidity, is compatible with unity for self-normalized charged-particle multiplicities beyond one. The measurements are compared with theoretical predictions incorporating initial or final state effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the ratio of branching fractions $\mathcal{B}\left({B}_c^{+}\to {B}_s^0{\pi}^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {\pi}^{+}\right)$

The ratio of branching fractions of ${B}_c^{+}\to {B}_s^0{\pi}^{+}$ and ${B}_c^{+}\to J/\psi {\pi}^{+}$ decays is measured with proton-proton collision data of a centre-of-mass energy of 13 TeV. The data were collected with the LHCb experiment during 2016–2018, corresponding to an integrated luminosity of 5.4 fb –1 . The ${B}_s^0$ mesons are reconstructed via the decays ${B}_s^0\to J/\psi \phi$ and ${B}_s^0\to {D}_s^{-}{\pi}^{+}$. The ratio of branching fractions is measured to be $\mathcal{B}\left({B}_c^{+}\to {B}_s^0{\pi}^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {\pi}^{+}\right)=91\pm 10\pm 8\pm 3$ where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Status of the PrimEx $\eta$ experiment at Jefferson Lab

The GlueX detector in the experimental Hall D at Jefferson Lab offers a unique opportunity to perform a measurement of the decay width of eta mesons through the Primakoff effect. The experiment complements the physics program at Jefferson Lab on measuring the decay width of light pseudoscalar mesons via the Primakoff process. The goal of the experiment is to measure differential cross sections of eta mesons at forward angles using a beam of tagged photons incident on a liquid 4He target, which will be used for the extraction of the decay width. This measurement is vital for understanding fundamental properties like the ratios of the light quark masses and the eta - eta' mixing angle, and will provide an important test of chiral symmetry breaking in QCD. Our experimental results will help reduce uncertainties on partial widths of all other eta decays. The experiment collected data during three physics runs between 2019 and 2022. We will give an overview of the PrimEx eta experiment and the current status of our data analyses. We will also discuss the feasibility of conducting future Primakoff measurements in light of the recent upgrade of the GlueX forward calorimeter and the potential accelerator energy upgrade to 22 GeV.

Somov, Alexander↗
DOE OSTI2023

𝐷-meson semileptonic decays to pseudoscalars from four-flavor lattice QCD

We present lattice-QCD calculations of the hadronic form factors for the semileptonic decays D → πℓν, D → Kℓν, and D s → Kℓν. Our calculation uses the highly improved staggered quark (HISQ) action for all valence and sea quarks and includes N f = 2 + 1 + 1 MILC ensembles with lattice spacings ranging from a ≈ 0.12 fm down to 0.042 fm. At most lattice spacings, an ensemble with physical-mass light quarks is included. The HISQ action allows all the quarks to be treated with the same relativistic light-quark action, allowing for nonperturbative renormalization using partial conservation of the vector current. We combine our results with experimental measurements of the differential decay rates to determine |V cd | D → π = 0.2238(11) Expt (15) QCD (04) EW (02) SIB [22] QED and |V cs | D → K = 0.9589 (23) Expt (40) QCD (15) EW (05) SIB [95] QED . This result for |V cd | is the most precise to date, with a lattice-QCD error that is, for the first time for the semileptonic extraction, at the same level as the experimental error. Using recent measurements from BES III, we also give the first-ever determination of |V cd | D s → K = 0.258(15) Expt (01) QCD [03] QED from D s → Klν. Our results also furnish new Standard Model calculations of the lepton flavor universality ratios $R$$^{D → π}_{μ/e}$ = 0.98671(17) QCD [500] QED , $R$$^{D → π}_{μ/e}$ = 0.97606(16) QCD [500] QED , and $R$$^{D → π}_{μ/e}$ = 0.98099(10) QCD [500] QED , which are consistent within 2σ with experimental measurements. Our extractions of |V cd | and |V cs |, when combined with a value for |V cb |, provide the most precise test of second-row Cabibbo-Kobayashi-Maskawa unitarity, finding agreement with unitarity at the level of one standard deviation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗