Nuclear Theory·nucl-th

Friday·November 1, 2019

12 papers—5 primary·7 cross-listed

06
The Soft Quark Sudakov
Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳
There has been recent interest in understanding the all loop structure of the subleading power soft and collinear limits, with the goal of achieving a systematic resummation of subleading power infrared logarithms. Most of this work has focused on subleading power corrections to soft gluon emission, whose form is strongly constrained by symmetries. In this paper we initiate a study of the all loop structure of soft fermion emission. In $N = 1$ QCD we perform an operator based factorization and resummation of the associated infrared logarithms, and prove that they exponentiate into a Sudakov due to their relation to soft gluon emission. We verify this result through explicit calculation to $O (α_{s}^{3})$ . We show that in QCD, this simple Sudakov exponentiation is violated by endpoint contributions proportional to $(C_{A} - C_{F})^{n}$ which contribute at leading logarithmic order. Combining our $N = 1$ result and our calculation of the endpoint contributions to $O (α_{s}^{3})$ , we conjecture a result for the soft quark Sudakov in QCD, a new all orders function first appearing at subleading power, and give evidence for its universality. Our result, which is expressed in terms of combinations of cusp anomalous dimensions in different color representations, takes an intriguingly simple form and also exhibits interesting similarities to results for large-x logarithms in the off diagonal splitting functions.
↳ hep-phhep-thnucl-thJHEP(2020)·77 citations
07
The Myriad Uses of Instantons
Robert D. Pisarski🇺🇸 · Fabian Rennecke🇺🇸
In quantum chromodynamics (QCD), the role which topologically non-trivial configurations play in splitting the singlet pseudo-Goldstone meson, the $η^{'}$ , from the octet is familiar. In addition, such configurations contribute to other processes which violate the axial $U (1)_{A}$ symmetry. While the nature of topological fluctuations in the confined phase is still unsettled, at temperatures well above that for the chiral phase transition, they can be described by a dilute gas of instantons. We show that instantons of arbitrary topological charge $Q$ generate anomalous interactions between $2 N_{f} ∣ Q ∣$ quarks, which for $Q = 1$ make the $η^{'}$ heavy. For two flavors we compute an anomalous quartic meson coupling and discuss its implications for the phenomenology of the chiral phase transition. A dilute instanton gas suggests that for cold, dense quarks, instantons do not evaporate until very high densities, when the baryon chemical potential is $≳ 2$ GeV.
↳ hep-phhep-thnucl-thPRD(2020)·26 citations
08
Invariant-mass spectroscopy of $^{14}$ O excited states
R.J. Charity🇺🇸 · K.W. Brown🇺🇸 · J. Okolowicz🇵🇱 · M. Ploszajczak🇫🇷 · J.E. Elson🇺🇸 · W. Reviol🇺🇸 · L.G. Sobotka🇺🇸 · W.W. Buhro🇺🇸 · Z. Chajecki🇺🇸 · W.G. Lynch🇺🇸 · J. Manfredi🇺🇸 · R. Shane🇺🇸 and 6 other authors
Excited states in $^{14}$ O have been investigated both experimentally and theoretically. Experimentally, these states were produced via neutron-knockout reactions with a fast $^{15}$ O beam and the invariant-mass technique was employed to isolate the 1 $p$ and 2 $p$ decay channels and determine their branching ratios. The spectrum of excited states was also calculated with the Shell Model Embedded in the Continuum that treats bound and scattering states in a unified model. By comparing energies, widths and decay branching patterns, spin and parity assignments for all experimentally observed levels below 8 MeV are made. This includes the location of the second 2 $^{+}$ state that we find is in near degeneracy with the third 0 $^{+}$ state. An interesting case of sequential 2 $p$ decay through a pair of degenerate $^{13}$ N excited states with opposite parities was found where the interference between the two sequential decay pathways produces an unusual relative-angle distribution between the emitted protons.
↳ nucl-exnucl-thPRC(2019)·19 citations
09
Prediction of $N Ω$ -like dibaryons with heavy quarks
Hongxia Huang🇨🇳 · Jialun Ping🇨🇳 · Fan Wang🇨🇳
Possible $N Ω$ -like dibaryons $N Ω_{ccc}$ and $N Ω_{bbb}$ with quantum numbers $I J^{P} = \frac{1}{2} 2^{+}$ are investigated within the framework of quark delocalization color screening model. We find both of these two states are bound, and the binding energy increases as the quarks of the system become heavier. The attraction between $N$ and $Ω_{ccc}$ (or $Ω_{bbb}$ ) mainly comes from the kinetic energy term due to quark delocalization and color screening. The effect of the channel-coupling provides more effective attraction to $N Ω_{ccc}$ and $N Ω_{bbb}$ systems. Besides, the scattering length, the effective range, and the binding energy, obtained from the calculation of the low-energy scattering phase shifts, also supports the existence of the $N Ω_{ccc}$ and $N Ω_{bbb}$ states. All these properties can provide necessary information for experimental search for the $N Ω$ -like dibaryons with heavy quarks. And the experimental progress can also check the mechanism of the intermediate-range attraction of the baryon-baryon interaction in quark models.
↳ hep-phnucl-thPRC(2020)·15 citations
10
Probing QCD critical fluctuations from the yield ratio of strange hadrons in relativistic heavy-ion collisions
Tianhao Shao🇨🇳 · Jinhui Chen🇨🇳 · Che Ming Ko🇺🇸 · Kai-Jia Sun🇺🇸
By analyzing the available data on strange hadrons in central Pb+Pb collisions from the NA49 Collaboration at the Super Proton Synchrotron (SPS) and in central Au+Au collisions from the STAR Collaboration at the Relativistic Heavy-Ion Collider (RHIC) in a wide collision energy range from $s_{NN}$ = 6.3 GeV to 200 GeV, we find a possible non-monotonic behavior in the ratio $\mathcal{O}_\text{K-$ \Xi $-$ \phi $-$ \Lambda $}$ = $\frac{N ( K ^{+} ) N ( Ξ ^{-} )}{N ( ϕ ) N ( Λ )}$ of $K^{+}$ , $Ξ^{-}$ , $ϕ$ , and $Λ$ yields as a function of $s_{NN}$ . Based on the quark coalescence model, which can take into account the effect of quark density fluctuations on hadron production, a possible non-monotonic behavior in the dependence of the strange quark density fluctuation on $s_{N N}$ is obtained. This is in contrast to the coalescence model that does not include quark density fluctuations and also to the statistical hadronization model as both fail to describe even qualitatively the collision energy dependence of the ratio $\mathcal{O}_\text{K-$ \Xi $-$ \phi $-$ \Lambda $}$ . Our findings thus suggest that the signal and location of a possible critical endpoint in the QCD phase diagram, which is expected to result in large quark density fluctuations, can be found in the on-going Bean Energy Scan program at RHIC.
↳ hep-phnucl-exnucl-thPLB(2020)·15 citations
11
Neutron-antineutron oscillations in the deuteron studied with $N N$ and $N ˉ N$ interactions based on chiral effective field theory
Johann Haidenbauer🇩🇪 · Ulf-G. Meißner🇩🇪
Neutron-antineutron ( $n - n ˉ$ ) oscillations in the deuteron are considered. Specifically, the deuteron lifetime is calculated in terms of the free-space $n - n ˉ$ oscillation time $τ_{n - n ˉ}$ based on $N N$ and $N ˉ N$ interactions derived within chiral effective field theory (EFT). This results in $(2.6 \pm 0.1) \times 1 0^{22} τ_{n - n ˉ}^{2}$ s, which is close to the value obtained by Dover and collaborators more than three decades ago, but disagrees with recent EFT calculations that were performed within the perturbative scheme proposed by Kaplan, Savage, and Wise. Possible reasons for the difference are discussed.
↳ hep-phnucl-thCPC(2020)·23 citations
12
Blast-wave description of $Υ$ elliptic flow at energies available at the CERN Large Hadron Collider
Klaus Reygers🇩🇪 · Alexander Schmah🇩🇪 · Anastasia Berdnikova🇷🇺 · Xu Sun🇺🇸
A simultaneous blast-wave fit to particle yields and elliptic flow ( $v_{2}$ ) measured as a function of transverse momentum in Pb-Pb collisions at LHC energies is presented. A compact formula for the calculation of $v_{2} (p_{T})$ for an elliptic freeze-out surface is used which follows from the Cooper-Frye ansatz without further assumptions. Over the full available $p_{T}$ range, the $Υ$ elliptic flow data is described by the prediction based on the fit to lighter particles. This prediction shows that, due to the large $Υ$ mass, a sizable elliptic flow is only expected at transverse momenta above 10 GeV/ $c$ .
↳ hep-phnucl-exnucl-thPRC(2020)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

The Soft Quark Sudakov

The Myriad Uses of Instantons

Invariant-mass spectroscopy of 14O excited states

Prediction of NΩ-like dibaryons with heavy quarks

Probing QCD critical fluctuations from the yield ratio of strange hadrons in relativistic heavy-ion collisions

Neutron-antineutron oscillations in the deuteron studied with NN and NˉN interactions based on chiral effective field theory

Blast-wave description of Υ elliptic flow at energies available at the CERN Large Hadron Collider

Affiliations

Invariant-mass spectroscopy of $^{14}$ O excited states

Prediction of $N Ω$ -like dibaryons with heavy quarks

Neutron-antineutron oscillations in the deuteron studied with $N N$ and $N ˉ N$ interactions based on chiral effective field theory

Blast-wave description of $Υ$ elliptic flow at energies available at the CERN Large Hadron Collider