Nuclear Theory·nucl-th

Thursday·April 1, 2021

8 papers—5 primary·3 cross-listed

06
Leading jets and energy loss
Duff Neill🇺🇸 · Felix Ringer🇺🇸 · Nobuo Sato🇺🇸
The formation and evolution of leading jets can be described by jet functions which satisfy non-linear DGLAP-type evolution equations. Different than for inclusive jets, the leading jet functions constitute normalized probability densities for the leading jet to carry a longitudinal momentum fraction relative to the initial fragmenting parton. We present a parton shower algorithm which allows for the calculation of leading-jet cross sections where logarithms of the jet radius and threshold logarithms are resummed to next-to-leading logarithmic (NLL $^{'}$ ) accuracy. By calculating the mean of the leading jet distribution, we are able to quantify the average out-of-jet radiation, the so-called jet energy loss. When an additional reference scale is measured, we are able to determine the energy loss of leading jets at the cross section level which is identical to parton energy loss at leading-logarithmic accuracy. We identify several suitable cross sections for an extraction of the jet energy loss and we present numerical results for leading subjets at the LHC. In addition, we consider hemisphere and event-wide leading jets in electron-positron annihilation similar to measurements performed at LEP. Besides the average energy loss, we also consider its variance and other statistical quantities such as the KL divergence which quantifies the difference between quark and gluon jet energy loss. We expect that our results will be particularly relevant for quantifying the energy loss of quark and gluon jets that propagate through hot or cold nuclear matter.
↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·32 citations
07
Thermodynamic stability, compressibility matrix, and effects of mediated interactions in a strongly-interacting Bose-Fermi mixture
Koki Manabe🇯🇵 · Yoji Ohashi🇯🇵
We theoretically investigate the thermodynamic stability of a normal-state Bose-Fermi mixture, with a tunable Bose-Fermi pairing interaction $- U_{BF} < 0$ associated with a hetero-nuclear Feshbach resonance, as well as a weak repulsive Bose-Bose interaction $U_{BB} \geq 0$ . Including strong hetero-pairing fluctuations associated with the former interaction within the self-consistent $T$ -matrix approximation, as well as the latter within the mean-field level, we calculate the compressibility matrix, to assess the stability of this system against density fluctuations. In the weak- and the intermediate-coupling regime with respect $- U_{BF}$ , we show that an effective attractive interaction between bosons mediated by density fluctuations in the Fermi component makes the system unstable below a certain temperature $T_{clp}$ (leading to density collapse). When $U_{BB} = 0$ , $T_{clp}$ is always higher than the Bose-Einstein condensation (BEC) temperature $T_{c}$ . When $U_{BB} > 0$ , the density collapse is suppressed, and the BEC transition becomes possible. It is also suppressed by the formation of tightly bound Bose-Fermi molecules when the hetero-pairing interaction $- U_{BF}$ is strong; however, since the system may be viewed as a molecular Fermi gas in this case, the BEC transition does not also occur. Since quantum gases involving Bose atoms are known to be sensitive to inter-particle correlations, our results would be useful for the study of many-body properties of a Bose-Fermi mixture in a stable manner, without facing the unwanted density collapse.
↳ cond-mat.quant-gasnucl-thPRA(2021)·4 citations
08
Intrinsic Glue and Wilson lines within Dressed Quarks
C. S. R. Costa🇧🇷 · Adam Freese🇺🇸 · Ian C. Cloët🇺🇸 · Bruno El-Bennich🇧🇷 · Gastão Krein🇧🇷 · Peter C. Tandy🇺🇸
We construct a quark target model (QTM) to incorporate intrinsic glue into effective low-energy models of QCD, which often contain only quark degrees of freedom. This method guarantees the gauge invariance of observables order-by-order in the strong coupling. The quark and gluon PDFs for the dressed quarks are obtained in the QTM at leading order. We demonstrate gauge invariance of the results by comparing both covariant and light cone gauges, with the former including an explicit Wilson line contribution. A key finding is that in covariant gauges the Wilson line can carry a significant amount of the light cone momentum. With coupling strength $α_{s} = 0.5$ and dressed quark mass $M_{q} = 0.4$ GeV, we find quark and gluon momentum fractions of $⟨ x ⟩_{q} = 0.81$ and $⟨ x ⟩_{g} = 0.19$ , where the Wilson line contribution to the quark momentum fraction is $- 0.18$ . We use the on-shell renormalization scheme and find that at one-loop this Wilson line contribution does not depend on the covariant gauge but does vanish in light cone gauge as expected. This result demonstrates that it is crucial to account for Wilson line contributions when calculating quantum correlation functions in covariant gauges. We also consider the impact of a gluon mass using the gauge invariant formalism proposed by Cornwall, and combine these QTM results with two quark-level models to obtain quark and gluon PDFs for the pion.
↳ hep-phnucl-thPRC(2021)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Leading jets and energy loss

Thermodynamic stability, compressibility matrix, and effects of mediated interactions in a strongly-interacting Bose-Fermi mixture

Intrinsic Glue and Wilson lines within Dressed Quarks

Affiliations