Thu·Nov 12, 2020Thursday·November 12, 2020

1. 01*

   Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and 2.76 TeV

   ALICE Collaboration

   Measurements of the production of muons from heavy-flavour hadron decays in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = $5.02$ and $2.76$ TeV using the ALICE detector at the LHC are reported. The nuclear modification factor $R_{\mathrm{AA}}$ at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV is measured at forward rapidity ($2.5<y<4$) as a function of transverse momentum $p_{\mathrm{T}}$ in central, semi-central, and peripheral collisions over a wide $p_{\mathrm{T}}$ interval, $3<p_{\mathrm{T}}<20$ GeV/$c$, in which muons from beauty-hadron decays are expected to take over from charm as the dominant source at high $p_{\mathrm{T}}$ ($p_{\mathrm{T}}>7$ GeV/$c$). The $R_{\mathrm{AA}}$ shows an increase of the suppression of the yields of muons from heavy-flavour hadron decays with increasing centrality. A suppression by a factor of about three is observed in the $10\%$ most central collisions. The $R_{\mathrm{AA}}$ at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 is similar to that at 2.76 TeV. The precise $R_{\mathrm{AA}}$ measurements have the potential to distinguish between model predictions implementing different mechanisms of parton energy loss in the high-density medium formed in heavy-ion collisions. They place important constraints for the understanding of the heavy-quark interaction with the hot and dense QCD medium.

   nucl-exhep-exPLB(2021)·28 citations
2. 02*

   ${\rm Y}$ production and nuclear modification at forward rapidity in Pb-Pb collisions at $\sqrt{{\text{s}}_{\text{NN}}}=5.02$ TeV

   ALICE Collaboration

   The production of ${\rm Y}$ mesons in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}$ = 5 TeV is measured with the muon spectrometer of the ALICE detector at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region $2.5<y<4.0$, as a function of rapidity, transverse momentum and collision centrality. The results show that the production of the ${\rm Y}$(1S) meson is suppressed by a factor of about three with respect to the production in proton-proton collisions. For the first time, a significant signal for the ${\rm Y}$(2S) meson is observed at forward rapidity, indicating a suppression stronger by about a factor 2-3 with respect to the ground state. The measurements are compared with transport, hydrodynamic, comover and statistical hadronisation model calculations.

   nucl-exhep-exPLB(2021)·82 citations
3. 03*

   Jet-associated deuteron production in pp collisions at $\sqrt{s}=13$ TeV

   ALICE Collaboration

   Deuteron production in high-energy collisions is sensitive to the space-time evolution of the collision system, and is typically described by a coalescence mechanism. For the first time, we present results on jet-associated deuteron production in \pp\ collisions at $\sqrt{s}=13$ TeV, providing an opportunity to test the established picture for deuteron production in events with a hard scattering. Using a trigger particle with high transverse-momentum ($p_{\mathrm{T}}>5$ GeV/$c$) as a proxy for the presence of a jet at midrapidity, we observe a measurable population of deuterons being produced around the jet proxy. The associated deuteron yield measured in a narrow angular range around the trigger particle differs by 2.4-4.8 standard deviations from the uncorrelated background. The data are described by PYTHIA model calculations featuring baryon coalescence.

   nucl-exhep-exPLB(2021)·24 citations
4. 04*

   Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   Jet fragmentation transverse momentum ($j_{\mathrm{T}}$) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-$k_{\mathrm{T}}$ algorithm with resolution parameter $R=0.4$ in the pseudorapidity range $|\eta |<0.25$. The $j_{\mathrm{T}}$ values are calculated for charged particles inside a fixed cone with a radius $R=0.4$ around the reconstructed jet axis. The measured $j_{\mathrm{T}}$ distributions are compared with a variety of parton-shower models. Herwig and PYTHIA 8 based models describe the data well for the higher $j_{\mathrm{T}}$ region, while they underestimate the lower $j_{\mathrm{T}}$ region. The $j_{\mathrm{T}}$ distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher $j_{\mathrm{T}}$ values (called the "wide component"), related to the perturbative component of the fragmentation process, and with a Gaussian for lower $j_{\mathrm{T}}$ values (called the "narrow component"), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.

   nucl-exhep-exJHEP(2021)·16 citations
5. 05*

   W-boson production in TMD factorization

   Daniel Gutierrez-Reyes🇪🇸 · Sergio Leal-Gomez🇦🇹 · Ignazio Scimemi🇪🇸

   At hadron colliders, the differential cross section for $W$ production can be factorized and it is sensitive transverse momentum dependent distributions (TMD) for low boson transverse momentum. While, often, the corresponding non-perturbative QCD contributions are extrapolated from $Z$ boson production, here we use an existing extraction (based on the code Artemide) of TMD which includes data coming from Drell-Yan and semi-inclusive deep inelastic scattering, to provide checks and predictions for the $W$ case. Including fiducial cuts with different configurations and kinematical power corrections, we consider transverse momentum dependent cross sections within several intervals of the vector boson transverse mass. We perform the same study for the $p_T^{W^{-}}/p_T^{W^{+}}$ and $p_T^Z/p_T^W$ distributions. We compare our predictions with recent extractions of these quantities at ATLAS and CMS and results from TeVatron. The results encourage a broader experimental and phenomenological work, and a deeper study of TMD for the $W$ case.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2021)·4 citations
6. 06*

   Neutron matter at finite temperature based on chiral effective field theory interactions

   J. Keller · C. Wellenhofer🇩🇪 · K. Hebeler🇩🇪 · A. Schwenk🇩🇪

   We study the equation of state of neutron matter at finite temperature based on two- and three-nucleon interactions derived within chiral effective field theory to next-to-next-to-next-to-leading order. The free energy, pressure, entropy, and internal energy are calculated using many-body perturbation theory including terms up to third order around the self-consistent Hartree-Fock solution. We include contributions from three-nucleon interactions without employing the normal-ordering approximation and provide theoretical uncertainty estimates based on an order-by-order analysis in the chiral expansion. Our results demonstrate that thermal effects can be captured remarkably well via a thermal index and a density-dependent effective mass. The presented framework provides the basis for studying the dense matter equation of state at general temperatures and proton fractions relevant for core-collapse supernovae and neutron star mergers.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2021)·69 citations
7. 07*

   Flavor-dependent radiative corrections in coherent elastic neutrino-nucleus scattering

   Oleksandr Tomalak🇺🇸 · Pedro Machado🇺🇸 · Vishvas Pandey🇺🇸 · Ryan Plestid🇺🇸

   We calculate coherent elastic neutrino-nucleus scattering cross sections on spin-0 nuclei (e.g. ${}^{40}$Ar and ${}^{28}$Si) at energies below 100 MeV within the Standard Model and account for all effects of permille size. We provide a complete error budget including uncertainties at nuclear, nucleon, hadronic, and quark levels separately as well as perturbative error. Our calculation starts from the four-fermion effective field theory to explicitly separate heavy-particle mediated corrections (which are absorbed by Wilson coefficients) from light-particle contributions. Electrons and muons running in loops introduce a nontrivial dependence on the momentum transfer due to their relatively light masses. These same loops, and those mediated by tau leptons, break the flavor universality because of mass-dependent electromagnetic radiative corrections. Nuclear physics uncertainties significantly cancel in flavor asymmetries resulting in subpercent relative errors. We find that for low neutrino energies, the cross section can be predicted with a relative precision that is competitive with neutrino-electron scattering. We highlight potentially useful applications of such a precise cross section prediction ranging from precision tests of the Standard Model, to searches for new physics and to the monitoring of nuclear reactors.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·91 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.