Thu·Aug 18, 2022Thursday·August 18, 2022

1. 01*

   Scaling of kinematical, global observables, energy and entropy densities in p+p, p+Pb and Pb+Pb collisions from 0.01 to 13 TeV

   Eleazar Cuautle🇲🇽 · Edgar Domínguez Rosas🇲🇽 · Mario Rodríguez-Cahuantzi🇲🇽

   The multiplicity and average transverse momentum of the charged and identified particles produced in different kinds of colliding systems are an example of global observables used to characterize events over a wide range of energy. Studying these observables provides insights into the collective phenomena and the geometric scaling properties of the systems created in ultra-relativistic p-Pb, Pb-Pb, and even in p-p collisions. The first part of this work presents a study of these variables using different Monte Carlo event generators. It analyzes their sensitivity to find collective phenomena at 0.01, 0.9, 2.76, 7, and 13 TeV, finding a less satisfactory description as the energy decreases. The second part analyzes the average transverse momentum of charged hadrons as a function of the multiplicity for p-p, p-Pb, and Pb-Pb data from the CMS and ALICE experiments. Comparing with Monte Carlo event generators, we look for a possible scaling law of average transverse momentum scaled to the overlap transverse collision area. Additionally, the experimental data are used to compute thermodynamical quantities such as the energy and entropy densities in the Bjorken approach. The results are compared with predictions from EPOS and PYTHIA Monte Carlo event generators. We observe an excellent agreement for <pT> from p-p but not for thermodynamical observables, where a sudden rise in a small <pT> range resembles the lattice QCD results for the $ϵ/T^4$ as a function of the temperature; however, only the experimental data from p-p show a kind of saturation.

   nucl-exhep-phJ.Phys.G(2022)·1 citation
2. 02*

   Nuclear-level Effective Theory of $\mu \to e$ Conversion: Formalism and Applications

   W. C. Haxton🇺🇸 · Evan Rule🇺🇸 · Ken McElvain🇺🇸 · Michael J. Ramsey-Musolf🇨🇳

   New mu-to-e conversion searches aim to advance limits on charged lepton flavor violation (CLFV) by four orders of magnitude. By considering P and CP selection rules and the structure of possible charge and current densities, we show that rates are governed by six nuclear responses. To generate a microscopic formulation of these responses, we construct in non-relativistic effective theory (NRET) the CLFV nucleon-level interaction, then embed it in a nucleus. We discuss previous work, noting the lack of a systematic treatment of the various small parameters. Because the momentum transfer is comparable to the inverse nuclear size, a full multipole expansion of the response functions is necessary, a daunting task with Coulomb-distorted electron partial waves. We perform such an expansion to high precision by introducing a simplifying local electron momentum, treating the full set of 16 NRET operators. Previous work has been limited to the simplest charge/spin operators, ignored Coulomb distortion (or alternatively truncated the partial wave expansion) and the nucleon velocity operator, which is responsible for three of the response functions. This generates inconsistencies in the treatment of small parameters. We obtain a "master formula" for mu-to-e conversion that properly treats all such effects and those of the muon velocity. We compute muon-to-electron conversion rates for a series of experimental targets, deriving bounds on the coefficients of the CLFV operators. We discuss the nuclear physics: two types of coherence enhance certain CLFV operators and selection rules blind elastic mu-to-e conversion to others. We discuss the matching of the NRET onto higher level EFTs, and the relation to mu-to-e conversion to other CLFV tests. Finally we describe a publicly available script that can be used to compute mu-to-e conversion rates in nuclear targets.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·37 citations
3. 03*

   Bayesian analysis of QGP jet transport using multi-scale modeling applied to inclusive hadron and reconstructed jet data

   R. Ehlers · A. Angerami · R. Arora · S. A. Bass · S. Cao · Y. Chen · L. Du · T. Dai · H. Elfner · W. Fan · R. J. Fries · C. Gale and 46 other authors

   The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitative comparison of model calculations and data. The multi-stage framework incorporates multiple models to cover a broad range in scale of the in-medium parton shower evolution, with dynamical choice of model that depends on the current virtuality or energy of the parton. We will discuss the physics of the multi-stage modeling, and then present a new Bayesian analysis incorporating it. This analysis extends the recently published JETSCAPE determination of the jet transport parameter $\hat{q}$ that was based solely on inclusive hadron suppression data, by incorporating reconstructed jet measurements of quenching. We explore the functional dependence of jet transport coefficients on QGP temperature and jet energy and virtuality, and report the consistency and tensions found for current jet quenching modeling with hadron and reconstructed jet data over a wide range in kinematics and $\sqrt{s_{\text{NN}}}$. This analysis represents the next step in the program of comprehensive analysis of jet quenching phenomenology and its constraint of properties of the QGP.

   ↳ hep-phnucl-exnucl-thActa Phys.Polon.Supp.(2023)·12 citations
4. 04*

   Neutrinos in Stellar Astrophysics

   G. M. Fuller · W. C. Haxton

   The physics of the mysterious and stealthy neutrino is at the heart of many phenomena in the cosmos. These particles interact with matter and with each other through the aptly named weak interaction. At typical astrophysical energies the weak interaction is some twenty orders of magnitude weaker than the electromagnetic interaction. However, in the early universe and in collapsing stars neutrinos can more than make up for their feeble interaction strength with huge numbers. Neutrinos can dominate the dynamics in these sites and set the conditions that govern the synthesis of the elements. Here we journey through the history of the discovery of these particles and describe their role in stellar evolution and collapse, the big bang, and multi-messenger astrophysics. Neutrino physics is at the frontier of elementary particle physics, nuclear physics, astrophysics and cosmology. All of these fields overlap in the neutrino story.

   ↳ nucl-thastro-ph.SRhep-exnucl-ex11 citations
5. 05*

   Unraveling Gluon Jet Quenching through $J/\psi$ Production in Heavy-Ion Collisions

   Shan-Liang Zhang🇨🇳 · Jinfeng Liao🇺🇸 · Guang-You Qin🇨🇳 · Enke Wang🇨🇳 · Hongxi Xing🇨🇳

   Jet quenching has long been regarded as one of the key signatures for the formation of quark-gluon plasma in heavy-ion collisions. Despite significant efforts, the separate identification of quark and gluon jet quenching has remained as a challenge. Here we show that $J/\psi$ in high transverse momentum ($p_{\text{T}}$) region provides a uniquely sensitive probe of in-medium gluon energy loss since its production at high $p_{\text{T}}$ is particularly dominated by gluon fragmentation. Such gluon-dominance is first demonstrated for the baseline of proton-proton collisions within the framework of leading power NRQCD factorization formalism. We then use the linear Boltzmann transport model combined with hydrodynamics for the simulation of jet-medium interaction in nucleus-nucleus collisions. The satisfactory description of experimental data on both nuclear modification factor $R_{\text{AA}}$ and elliptic flow $v_2$ reveals, for the first time, that the gluon jet quenching is the driving force for high $p_{\text{T}}$ $J/\psi$ suppression. This novel finding is further confirmed by the data-driven Bayesian analyses of relevant experimental measurements, from which we also obtain the first quantitative extraction of the gluon energy loss distribution in the quark-gluon plasma.

   ↳ hep-phhep-exnucl-exnucl-thSci.Bull.(2023)·17 citations
6. 06*

   Evidence for intrinsic charm quarks in the proton

   Richard D. Ball🇬🇧 · Alessandro Candido🇮🇹 · Juan Cruz-Martinez🇮🇹 · Stefano Forte🇮🇹 · Tommaso Giani🇳🇱 · Felix Hekhorn🇮🇹 · Kirill Kudashkin🇮🇹 · Giacomo Magni🇳🇱 · Juan Rojo🇳🇱

   The theory of the strong force, quantum chromodynamics, describes the proton in terms of quarks and gluons. The proton is a state of two up quarks and one down quark bound by gluons, but quantum theory predicts that in addition there is an infinite number of quark-antiquark pairs. Both light and heavy quarks, whose mass is respectively smaller or bigger than the mass of the proton, are revealed inside the proton in high-energy collisions. However, it is unclear whether heavy quarks also exist as a part of the proton wavefunction, which is determined by non-perturbative dynamics and accordingly unknown: so-called intrinsic heavy quarks. It has been argued for a long time that the proton could have a sizable intrinsic component of the lightest heavy quark, the charm quark. Innumerable efforts to establish intrinsic charm in the proton have remained inconclusive. Here we provide evidence for intrinsic charm by exploiting a high-precision determination of the quark-gluon content of the nucleon based on machine learning and a large experimental dataset. We disentangle the intrinsic charm component from charm-anticharm pairs arising from high-energy radiation. We establish the existence of intrinsic charm at the 3-standard-deviation level, with a momentum distribution in remarkable agreement with model predictions. We confirm these findings by comparing to very recent data on Z-boson production with charm jets from the LHCb experiment.

   ↳ hep-phhep-exhep-latnucl-ex+1Nature(2022)·132 citations

* 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.