Nuclear Theory·nucl-th

Tuesday·April 14, 2020

20 papers—10 primary·10 cross-listed

11
$Z$ plus jets production via double parton scattering in $p A$ collisions at the LHC
B. Blok🇮🇱 · F. A. Ceccopieri (Technion)🇮🇱
We present results on Zjj production via double parton scattering in pA collisions at the LHC. We perform the analysis at leading and next-leading order accuracy with different sets of cuts on jet transverse momenta and accounting for the single parton scattering background. By exploiting the experimental capability to measure the centrality dependence of the cross section, we discuss the feasibility of DPS observation in already collected data at the LHC and in future runs.
↳ hep-phhep-exnucl-exnucl-thEPJC(2020)·4 citations
12
Non-equilibrium attractor in high-temperature QCD plasmas
Dekrayat Almaalol🇺🇸 · Aleksi Kurkela🇨🇭 · Michael Strickland🇺🇸
We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing one-dimensional Bjorken expansion. We demonstrate that the resulting far-from-equilibrium evolution is insensitive to certain features of the initial condition, including both the initial momentum-space anisotropy and initial occupancy. We find that this insensitivity extends beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. Based on our results, we assess different procedures for reconstructing the full one-particle distribution function from the energy-momentum tensor along the attractor and discuss implications for the freeze-out procedure used in the phenomenological analysis of ultra-relativistic nuclear collisions.
↳ hep-phnucl-thPRL(2020)·92 citations
13
How EIC can help us to understand heavy-ion collisions
Yoshitaka Hatta🇺🇸
I give a brief overview of the science cases of the Electron-Ion Collider (EIC) with a particular emphasis on the connections to the physics of ultrarelativistic heavy-ion collisions.
↳ hep-phnucl-exnucl-thNPA(2021)·4 citations
14
First measurement of direct photoproduction of the $a_{2} (1320)^{0}$ meson on the proton
A. Celentano · M. Battaglieri · R. De Vita · L. Marsicano · V. Mathieu · A. Pilloni · A. Szczepaniak (for the CLAS collaboration)
We present the first measurement of the exclusive reaction $γ p \to a_{2} (1320)^{0} p$ in the photon energy range $3.5$ - $5.5$ GeV and four-momentum transfer squared $0.2 < - t < 2.0$ GeV $^{2}$ . Data were collected with the CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Accelerator Facility. The neutral $a_{2}$ resonance was detected by measuring the reaction $γ p \to π^{0} η p$ and reconstructing the $π^{0} η$ invariant mass. The differential cross section $d σ / d t$ was extracted at different beam energies in each $- t$ bin. The most prominent feature of the differential cross section is a dip at $- t ≃ 0.55$ GeV $^{2}$ . This can be well described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer.
↳ nucl-exhep-exnucl-thPRC(2020)·12 citations
15
Nonequilibrium pion distribution within the Zubarev approach
David Blaschke🇵🇱 · Gerd Röpke🇷🇺 · Dmitry N. Voskresensky🇷🇺 · Vladimir G. Morozov🇷🇺
We discuss how the nonequilibrium process of pion production within the Zubarev approach of the nonequilibrium statistical operator leads to a theoretical foundation for the appearance of a nonequilibrium pion chemical potential for the pion distribution function for which there is experimental evidence in experiments at the CERN LHC.
↳ hep-phcond-mat.stat-mechnucl-thParticles(2020)·8 citations
16
Classical excluded volumes of loosely bound light (anti)nuclei and their chemical freeze-out in heavy ion collisions
B. E. Grinyuk🇺🇦 · K. A. Bugaev🇺🇦 · V. V. Sagun🇵🇹 · O. I. Ivanytskyi🇵🇹 · D. L. Borisyuk🇺🇦 · A. S. Zhokhin🇺🇦 · G. M. Zinovjev🇺🇦 · D. B. Blaschke🇵🇱 · L. V. Bravina🇳🇴 · E. E. Zabrodin🇳🇴 · E. G. Nikonov🇷🇺 · G. Farrar🇺🇸 and 3 other authors
From the analysis of light (anti)nuclei multiplicities that were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy $s_{N N} = 2.76$ TeV there arose a highly non-trivial question about the excluded volume of composite particles. Surprisingly, the hadron resonance gas model (HRGM) is able to perfectly describe the light (anti)nuclei multiplicities under various assumptions. Thus, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. It is clear, however, that such assumptions are unphysical. Hence we obtain a formula for the classical excluded volume of loosely bound light nuclei consisting of A baryons. To implement a new formula into the HRGM we have to modify the induced surface tension concept to treat the hadrons and (anti)nuclei on the same footing. We perform a simultaneous analysis of hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The HRGM with the induced surface tension allows us to verify different assumptions on the values of hard-core radii and different scenarios of chemical freeze-out of light (anti)nuclei. It is shown that the unprecedentedly high quality of fit $χ_{t o t}^{2} / d o f ≃ 0.769$ is achieved, if the chemical freeze-out temperature of hadrons is about $T_{h} = 150$ MeV, while the one for all (anti)nuclei is $T_{A} = 174 - 175.2$ MeV.
↳ hep-phnucl-exnucl-thIJMPE(2020)·7 citations
17
Non-Hermitian Ferromagnetism in an Ultracold Fermi Gas
Hiroyuki Tajima · Kei Iida
We develop a non-Hermitian effective theory for a repulsively interacting Fermi gas in the excited branch. The on-shell $T$ -matrix is employed as a complex-valued interaction term, which describes a repulsive interaction between atoms in the excited branch and a two-body inelastic decay to the attractive branch. To see the feature of this model, we have addressed, in the weak coupling regime, the excitation properties of a repulsive Fermi polaron as well as the time-dependent number density. The analytic expressions obtained for these quantities qualitatively show a good agreement with recent experiments. By calculating the dynamical transverse spin susceptibility in the random phase approximation, we show that a ferromagnetic system with nonzero polarization undergoes a dynamical instability and tends towards a heterogeneous phase.
↳ cond-mat.quant-gasnucl-thJ.Phys.Soc.Jap.(2021)·3 citations
18
Heavy-hadron molecules from light-meson-exchange saturation
Fang-Zheng Peng🇨🇳 · Ming-Zhu Liu🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Manuel Pavon Valderrama🇨🇳
In the effective field theory framework the interaction between two heavy hadrons can be decomposed into a long- and a short-range piece. The long-range piece corresponds to the one-pion-exchange potential and is relatively well-known. The short-range piece is given by a series of contact-range interactions with unknown couplings, which substitute the less well-known short-range dynamics. While the general structure of the short-range potential between heavy hadrons is heavily constrained from heavy-quark symmetry, the couplings are still free parameters. Here we argue that the relative strength and the sign of these couplings can be estimated from the hypothesis that they are saturated by the exchange of light mesons, in particular the vector mesons $ρ$ and $ω$ , i.e. from resonance saturation. However, we propose a novel saturation procedure that effectively removes form-factor artifacts. From this we can determine in which spin and isospin configurations the low-energy constants are most attractive for specific two-heavy-hadron systems. In general the molecular states with lower isospins and higher spins will be more attractive and thus more probable candidates to form heavy-hadron molecules. This pattern is compatible with the interpretation of the $X (3872)$ and $P_{c} (4312/4440/4457)$ as molecular states, but it is not applicable to states with maximum isospin like the $Z_{c} (3900/4020)$ .
↳ hep-phhep-exhep-latnucl-thPRD(2020)·37 citations
19
Relativistic Borromean States
Ziyue Wang🇨🇳 · Shao-Jian Jiang🇨🇳 · Yin Jiang🇨🇳
In this work the existence of Borromean states has been discussed for bosonic and fermionic cases in both the relativistic and non-relativistic limits from the 3-momentum shell renormalization. With the linear bosonic model we checked the existence of Efimov-like states in the bosonic system. In both limits a geometric series of singularities are found in the 3-boson interaction vertex, while the energy ratio is reduced by around 70\% in the relativistic limit because of the anti-particle contribution. Motivated by the quark-diquark model in heavy baryon studies, we have carefully examined the p-wave quark-diquark interaction and found an isolated Borromean pole at finite energy scale. This may indicate a special baryonic state of light quarks in high energy quark matters. In other cases trivial results are obtained as expected. In relativistic limit, for both bosonic and fermionic cases, potential Borromean states are independent of the mass, which means the results would be valid even in zero-mass limit as well.
↳ hep-phcond-mat.quant-gashep-thnucl-thCPC(2021)·0 citations
20
NS 1987A in SN 1987A
Dany Page · Mikhail V. Beznogov · Iván Garibay · James M. Lattimer · Madappa Prakash · Hans-Thomas Janka
The possible detection of a compact object in the remnant of SN 1987A presents an unprecedented opportunity to follow its early evolution. The suspected detection stems from an excess of infrared emission from a dust blob near the compact object's predicted position. The infrared excess could be due to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or black hole, magnetospheric emission or a wind originating from the spindown of a pulsar, or thermal emission from an embedded, cooling neutron star (NS 1987A). It is shown that the last possibility is the most plausible as the other explanations are disfavored by other observations and/or require fine-tuning of parameters. Not only are there indications the dust blob overlaps the predicted location of a kicked compact remnant, but its excess luminosity also matches the expected thermal power of a 30 year old neutron star. Furthermore, models of cooling neutron stars within the Minimal Cooling paradigm readily fit both NS 1987A and Cas A, the next-youngest known neutron star. If correct, a long heat transport timescale in the crust and a large effective stellar temperature are favored, implying relatively limited crustal n-1S0 superfluidity and an envelope with a thick layer of light elements, respectively. If the locations don't overlap, then pulsar spindown or accretion might be more likely, but the pulsar's period and magnetic field or the accretion rate must be rather finely tuned. In this case, NS 1987A may have enhanced cooling and/or a heavy-element envelope.
↳ astro-ph.HEnucl-thApJ(2020)·85 citations

Affiliations

first authorsco-authorsvia INSPIRE