Mon·Jul 31, 2023Monday·July 31, 2023

1. 01*

   Low-$x$ physics at LHCb

   Thomas Boettcher🇺🇸

   The LHCb detector's forward geometry provides unprecedented kinematic coverage at low Bjorken-$x$. LHCb's excellent momentum resolution, vertex reconstruction, and particle identification enable precision measurements at low transverse momentum and high rapidity in proton-lead collisions, probing $x$ as small as $10^{-6}$. In this contribution, we present recent studies of low-$x$ physics using the LHCb detector. These studies include charged hadron, neutral pion, and $D^0$ production in proton-lead collisions, as well as charmonium production in ultraperipheral lead-lead collisions. Future prospects and implications for the understanding of low-$x$ nuclear PDFs and parton saturation are also discussed.

   nucl-exhep-ex0 citations
2. 02*

   Measurement of leading charged-particle jet properties in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ALICE

   Prottoy Das (for the ALICE Collaboration)🇮🇳

   Jets are collimated sprays of particles produced from the fragmentation and hadronization of hard-scattered partons in high energy hadronic and nuclear collisions. Jet properties are sensitive to details of parton showering processes and are expected to be modified in the presence of a dense partonic medium. Measurement of intra-jet properties in p--Pb collisions will help to investigate cold nuclear matter effects and enrich our current understanding of particle production in such collision systems. In this work, we present the measurement of leading charged-particle jet properties, namely the mean charged-particle multiplicity and the fragmentation functions, in the range of jet $p_{\mathrm{T}}$ 10 -- 100 GeV/c at midrapidity in minimum bias p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ALICE. Results are compared with theoretical model predictions.

   nucl-exhep-exSpringer Proc.Phys.(2024)·0 citations
3. 03*

   Ab initio calculations of neutrinoless $\beta \beta$ decay refine neutrino mass limits

   A. Belley🇨🇦 · T. Miyagi🇩🇪 · S. R. Stroberg🇺🇸 · J. D. Holt🇨🇦

   Neutrinos are perhaps the most elusive known particles in the universe. We know they have some nonzero mass, but unlike all other particles, the absolute scale remains unknown. In addition, their fundamental nature is uncertain; they can either be their own antiparticles or exist as distinct neutrinos and antineutrinos. The observation of the hypothetical process of neutrinoless double-beta ($0\nu \beta \beta$) decay would at once resolve both questions, while providing a strong lead in understanding the abundance of matter over antimatter in our universe. In the scenario of light-neutrino exchange, the decay rate is governed by, and thereby linked to the effective mass of the neutrino via, the theoretical nuclear matrix element (NME). In order to extract the neutrino mass, if a discovery is made, or to assess the discovery potential of next-generation searches, it is essential to obtain accurate NMEs for all isotopes of experimental interest. However, two of the most important cases, ${}^{130}$Te and ${}^{136}$Xe, lie in the heavy region and have only been accessible to phenomenological nuclear models. In this work we utilize powerful advances in ab initio nuclear theory to compute NMEs from the underlying nuclear and weak forces driving this decay, including the recently discovered short-range component. We find that ab initio NMEs are generally smaller than those from nuclear models, challenging the expected reach of future ton-scale searches as well as claims to probe the inverted hierarchy of neutrino masses. With this step, ab initio calculations with theoretical uncertainties are now feasible for all isotopes relevant for next-generation $0\nu \beta \beta$ decay experiments.

   ↳ nucl-thhep-exhep-phnucl-ex41 citations
4. 04*

   Central Speed of Sound, Trace Anomaly and Observables of Neutron Stars from Perturbative Analyses of Scaled TOV Equations

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸 · Zhen Zhang🇨🇳

   The central speed of sound (SS) measures the stiffness of the Equation of State (EOS) of superdense neutron star (NS) matter. Its variations with density and radial coordinate in NSs in conventional analyses often suffer from uncertainties of the specific nuclear EOSs used. Using the central SS and NS mass/radius scaling obtained from solving perturbatively the scaled Tolman-Oppenheimer-Volkoff (TOV) equations, we study the variations of SS, trace anomaly and several closely related properties of NSs in an EOS-model independent manner. We find that the SS increases with the reduced central pressure ${\hat{P}}_{\mathrm{c}}\equiv P_{\mathrm{c}}/{\epsilon }_{\mathrm{c}}$ (scaled by the central energy density ${\epsilon }_{\mathrm{c}}$), and the conformal bound for SS tends to break down for NSs with masses higher than about 1.9$M_{\odot }$. The ratio $P/\epsilon$ is upper bounded as $P/\epsilon \lesssim 0.374$ around the centers of stable NSs. We demonstrate that it is an intrinsic property of strong-field gravity and is more relevant than the perturbative QCD bound on it. While a sharp phase transition at high densities characterized by a sudden vanishing of SS in cores of massive NSs are basically excluded, the probability for a continuous crossover signaled by a peaked radial profile of SS is found to be enhanced as ${\hat{P}}_{\mathrm{c}}$ decreases, implying it likely happens near the centers of massive NSs. Moreover, a new and more stringent causality boundary as $R_{\max }/\mathrm{km}\gtrsim 4.73{\mathrm{M}}_{\mathrm{NS}}^{\max }/{\mathrm{M}}_{\odot }+1.14$ for NS M-R curve is found to be excellently consistent with observational data on NS masses and radii. Furthermore, new constraints on the ultimate energy density and pressure allowed in NSs before collapsing into black holes are obtained and compared with earlier predictions in the literature.

   ↳ nucl-thastro-ph.HEnucl-exPRD(2023)·23 citations
5. 05*

   BlueSTEAl: A pair of silicon arrays and a zero-degree phoswich detector for studies of scattering and reactions in inverse kinematics

   Shuya Ota🇯🇵 · Greg Christian · Ben J. Reed · Wilton N. Catford🇬🇧 · Stefania Dede🇺🇸 · Daniel T. Doherty · Gavin Lotay · Michael Roosa🇺🇸 · Antti Saastamoinen🇺🇸 · Dustin P. Scriven🇺🇸

   BlueSTEAl, the Blue (aluminum chamber of) Silicon TElescope Arrays for light nuclei,has been developed to study direct reactions in inverse kinematics, as well as scattering and breakup reactions using radioactive ion beams. It is a detector system consisting of a pair of annular silicon detector arrays and a zero-degree phoswich plastic scintillator. For typical binary reaction studies in inverse kinematics, light ions are detected by the Si array in coincidence with heavy recoils detected by the phoswich placed at the focal-plane of a zero-degree magnetic spectrometer. The Si array can also be used to detect light nuclei such as berylium and carbon with clear isotope separation, while the phoswich can also be placed at zero degrees without a spectrometer and used as a high-efficiency beam counting monitor with particle identification capability at the rate of up to 5*10^4 particles per second. This paper reports on the capabilities of BlueSTEAl as determined by recent experiments performed at the Texas A&M Cyclotron Institute. The device is also anticipated to be used in future experiments at other radioactive ion beam facilities.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2024)·3 citations
6. 06*

   Energy Correlators on Tracks: Resummation and Non-Perturbative Effects

   Max Jaarsma🇳🇱 · Yibei Li🇨🇳 · Ian Moult🇺🇸 · Wouter J. Waalewijn🇳🇱 · Hua Xing Zhu🇨🇳

   Energy correlators measured inside high-energy jets at hadron colliders have recently been demonstrated to provide a new window into both perturbative and non-perturbative Quantum Chromodynamics. A number of the most interesting features of these correlators, namely their universal scaling behavior and the ability to image the confinement transition, require precise angular resolution, necessitating the use of tracking information in experimental measurements. Theoretically, tracking information can be incorporated into the energy correlators using track functions, which are non-perturbative functions describing the fragmentation of quarks and gluons into charged hadrons. In this paper, we apply our recently developed track function formalism to energy correlators, and study in detail the interplay of track functions with perturbative resummation and non-perturbative power corrections. We provide resummed results for the energy correlators at collinear next-to-leading-logarithmic accuracy and compare with parton shower Monte Carlo simulations. For the two-point correlator the use of tracking has a minimal effect throughout the entire distribution, but it has a significant effect for higher point correlators. Our results are crucial for the theoretical interpretation of recent experimental measurements of the energy-energy correlators.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2023)·64 citations
7. 07*

   Predicted Measurements of the Tensor-to-Scalar Transition in the CLAS12 Nuclear Targets Experiment

   Erin Marshall Seroka🇺🇸 · Axel Schmidt🇺🇸

   Short-range correlated (SRC) nucleon pairs, which are strongly interacting nucleons at short inter-particle distances, can reveal properties of the effective nucleon-nucleon (\textit{NN}) interaction at short distance scales. The relative abundance of proton-proton (\textit{pp}) pairs and proton-neutron (\textit{pn}) pairs, for example, is sensitive to the tensor contribution to the \textit{NN} interaction. Generalized Contact Formalism (GCF) theory, when used with realistic phenomenological \textit{NN} potential models, predicts a transition from a tensor-dominated regime -- at relative momenta of approximately 400~MeV/\textit{c} where \textit{pp} pairs are suppressed relative to \textit{pn} pairs -- to a scalar-dominated regime at higher momenta with no preferred isospin projection. While an increase in the prevalence of \textit{pp} pairs with increasing momentum has been observed in a few experiments, difficulties associated with neutron detection have so far hindered the observation of a corresponding reduction in the abundance of \textit{pn} pairs. High-precision measurements showing a simultaneous increase in the abundance of \textit{pp} pairs and change in the abundance of \textit{pn} pairs with increasing momentum would conclusively demonstrate the existence of the tensor-to-scalar transition. In this work, we study the potential impact of the recently conducted Nuclear Targets Experiment at the CLAS12 detector at Jefferson Lab, using GCF simulations. We model the expected yields and relevant observables for a carbon target with a beam energy of 6 GeV and show that sufficient statistical precision can be obtained from the experimental data, both for \textit{pp} and \textit{pn} pairs, to observe the tensor-to-scalar transition.

   ↳ nucl-thnucl-exEPJA(2023)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.