Nuclear Theory·nucl-th

Thursday·March 2, 2023

12 papers—6 primary·6 cross-listed

07
[Submitted on 8 Apr 2019] (cross-list from hep-ph)
The LPM effect in sequential bremsstrahlung: from large-N QCD to N=3 via the SU(N) analog of Wigner 6-j symbols
Peter Arnold🇺🇸
Consider a high-energy parton showering as it traverses a QCD medium such as a quark-gluon plasma. Interference effects between successive splittings in the shower are potentially very important but have so far been calculated (even in idealized theoretical situations) only in soft emission or large- $N_{c}$ limits, where $N_{c}$ is the number of quark colors. In this paper, we show how one may remove the assumption of large $N_{c}$ and so begin investigation of $N_{c} = 3$ without soft-emission approximations. Treating finite $N_{c}$ requires (i) classifying different ways that four gluons can form a color singlet and (ii) calculating medium-induced transitions between those singlets, for which we find application of results for the generalization of Wigner 6- $j$ symbols from angular momentum to SU( $N_{c}$ ). Throughout, we make use of the multiple scattering ( $q^$ ) approximation for high-energy partons crossing quark-gluon plasmas, and we find that this approximation is self-consistent only if the transverse-momentum diffusion parameter $q^$ for different color representations satisfies Casimir scaling (even for strongly-coupled, and not just weakly-coupled, quark-gluon plasmas). We also find that results for $N_{c} = 3$ depend, mathematically, on being able to calculate the propagator for a coupled non-relativistic quantum harmonic oscillator problem in which the spring constants are operators acting on a 5-dimensional Hilbert space of internal color states. Those spring constants are represented by constant $5 \times 5$ matrices, which we explicitly construct. We are unaware of any closed form solution for this type of harmonic oscillator problem, and we discuss prospects for using numerical evaluation.
Comments:
27 pages, 6 figures. Difference from v2: An erroneous assertion in section IV, that the two-dimensional harmonic oscillator problem could be reduced to one-dimensional harmonic oscillator problems, has been fixed
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1904.04264 [pdf]
PRD(2019)·14 citations
08
[Submitted on 9 Feb 2022] (cross-list from hep-ph)
The LPM Effect in sequential bremsstrahlung: $1/ N_{c}^{2}$ corrections
Peter Arnold🇺🇸 · Omar Elgedawy🇺🇸
An important question concerning in-medium high-energy parton showers in a quark-gluon plasma or other QCD medium is whether consecutive splittings of the partons in a given shower can be treated as quantum mechanically independent, or whether the formation times for two consecutive splittings instead have significant overlap. Various previous calculations of the effect of overlapping formation times have either (i) restricted attention to a soft bremsstrahlung limit, or else (ii) used the large- $N_{c}$ limit (where $N_{c} = 3$ is the number of quark colors). In this paper, we make a first study of the accuracy of the large- $N_{c}$ limit used by those calculations of overlap effects that avoid a soft bremsstrahlung approximation. Specifically, we calculate the $1/ N_{c}^{2}$ correction to previous $N_{c} = \infty$ results for overlap $g \to g g \to g g g$ of two consecutive gluon splittings $g \to g g$ . At order $1/ N_{c}^{2}$ , there is interesting and non-trivial color dynamics that must be accounted for during the overlap of the formation times.
Comments:
47 pages, 19 figures. Changes from v1: some clarification added through new footnotes and a new figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2202.04662 [pdf]
JHEP(2022)·12 citations
09
[Submitted on 28 Feb 2023] (cross-list from astro-ph.HE)
What neutron stars tell about the hadron-quark phase transition: a Bayesian study
János Takátsy🇭🇺 · Péter Kovács🇭🇺 · György Wolf🇭🇺 · Jürgen Schaffner-Bielich🇩🇪
The existence of quark matter inside the heaviest neutron stars has been the topic of numerous recent studies, many of them suggesting that a phase transition to strongly interacting conformal matter inside neutron stars is feasible. Here we examine this hybrid star scenario using a soft and a stiff hadronic model, a constituent quark model with three quark flavours, and applying a smooth crossover transition between the two. Within a Bayesian framework, we study the effect of up-to-date constraints from neutron star observations on the equation-of-state parameters and various neutron star observables. Our results show that a pure quark core is only possible if the maximum mass of neutron stars is below $\sim 2.35 M_{⊙}$ . However, we also find, consistently with other studies, that a peak in the speed of sound, exceeding $1/3$ , is highly favoured by astrophysical measurements, which might indicate the percolation of hadrons at $\sim 3 - 4 n_{0}$ . Even though our prediction for the phase transition parameters varies depending on the specific astrophysical constraints utilized, the position of the speed of sound peak only changes slightly, while the existence of pure quark matter below $\sim 4 n_{0}$ , using our parameterization, is disfavoured. On the other hand, the preferred range for the EoS shows signs of conformality above $\sim 4 n_{0}$ . Additionally, we present the difference in the upper bounds of radius estimates using the full probability density data and sharp cut-offs, and stress the necessity of using the former.
Comments:
23 pages, 13 figures, accepted by Phys. Rev. D
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2303.00013 [pdf]
PRD(2023)·63 citations
10
[Submitted on 28 Feb 2023] (cross-list from nucl-ex)
Quantum Information Science and Technology for Nuclear Physics. Input into U.S. Long-Range Planning, 2023
Douglas Beck · Joseph Carlson · Zohreh Davoudi · Joseph Formaggio · Sofia Quaglioni · Martin Savage · Joao Barata · Tanmoy Bhattacharya · Michael Bishof · Ian Cloet · Andrea Delgado · Michael DeMarco and 89 other authors
In preparation for the 2023 NSAC Long Range Plan (LRP), members of the Nuclear Science community gathered to discuss the current state of, and plans for further leveraging opportunities in, QIST in NP research at the Quantum Information Science for U.S. Nuclear Physics Long Range Planning workshop, held in Santa Fe, New Mexico on January 31 - February 1, 2023. The workshop included 45 in-person participants and 53 remote attendees. The outcome of the workshop identified strategic plans and requirements for the next 5-10 years to advance quantum sensing and quantum simulations within NP, and to develop a diverse quantum-ready workforce. The plans include resolutions endorsed by the participants to address the compelling scientific opportunities at the intersections of NP and QIST. These endorsements are aligned with similar affirmations by the LRP Computational Nuclear Physics and AI/ML Workshop, the Nuclear Structure, Reactions, and Astrophysics LRP Town Hall, and the Fundamental Symmetries, Neutrons, and Neutrinos LRP Town Hall communities.
Comments:
A white paper for the 2023 nuclear physics long-range planning activity, emerging from the workshop "Quantum Information Science for U.S. Nuclear Physics Long Range Planning'', held in Santa Fe, New Mexico on January 31 - February 1, 2023. 26 pages with 7 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2303.00113 [pdf]
67 citations
11
[Submitted on 28 Feb 2023] (cross-list from hep-ph)
Deeply-virtual Compton process $e^{-} N \to e^{-} γ π N$ to study nucleon to resonance transitions
Kirill M. Semenov-Tian-Shansky🇰🇷 · Marc Vanderhaeghen🇩🇪
We study the deeply-virtual Compton scattering (DVCS) process $e^{-} N \to e^{-} γ π N$ involving the transition between a nucleon and a nucleon resonance in the $π N$ system, within the framework of generalized parton distributions (GPDs). For the four lowest-lying nucleon resonances, $Δ (1232)$ , $P_{11} (1440)$ , $D_{13} (1520)$ , and $S_{11} (1535)$ , we express the DVCS amplitude in the Bjorken limit in terms of corresponding nucleon-to-resonance GPDs. Building upon the knowledge of the well studied electromagnetic nucleon-to-resonance transition form factors, which map the quark charge densities in transverse position space, the corresponding GPDs will open the prospect to also access the longitudinal momentum distributions of quarks in the transition. We provide estimates for cross sections and beam-spin asymmetries in the first and second $π N$ resonance regions in the kinematics of forthcoming CLAS12 data from Jefferson Lab.
Comments:
23 pages, 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2303.00119 [pdf]
PRD(2023)·24 citations
12
[Submitted on 1 Mar 2023] (cross-list from nucl-ex)
Coexistence of single particle and collective excitation in $^{61}$ Ni
Soumik Bhattacharya · Vandana Tripathi · E. Rubino · Samuel Ajayi · L. T. Baby · C. Benetti · R. S. Lubna · S. L. Tabor · J. Döring · Y. Utsuno · N. Shimizu · J. M. Almond · G. Mukherjee
The high spin states in 61 Ni have been studied using the fusion evaporation reaction, Ti( $^{14}$ C,3n) $^{61}$ Ni at an incident beam energy of 40 MeV. A Compton suppressed multi-HPGe detector setup, consisting of six Clover detectors and three single crystal HPGe detectors was used to detect the de-exciting $γ$ rays from the excited states. The level scheme has been extended up to an excitation energy of 12.8 MeV and a tentative J $_{π}$ = 35/2 $^{+}$ . The low-lying negative parity levels are found to be generated by single particle excitation within the f p shell and also excitations to the g $_{9/2}$ orbitals as explained well with shell model calculations using the GXPF1Br+V M U (modified) interaction. Two rotational structure of regular E2 sequences with small to moderate axial deformation have been established at higher excitation energy. Most interestingly, two sequences of M1 transitions are reported for the first time and described as magnetic rotational bands. The shears mechanism for both the bands can be described satisfactorily by the geometrical model. The shell model calculation involving the cross shell excitation beyond the fp shell well reproduce the M1 and E2 sequences. The shell model predicted B(M1) values for the magnetic rotational band B1 show the decreasing trend with spin as expected with closing of the shears.
Comments:
18 pages, 17 Fig
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2303.00588 [pdf]
PRC(2023)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

The LPM effect in sequential bremsstrahlung: from large-N QCD to N=3 via the SU(N) analog of Wigner 6-j symbols

The LPM Effect in sequential bremsstrahlung: 1/Nc2​ corrections

What neutron stars tell about the hadron-quark phase transition: a Bayesian study

Quantum Information Science and Technology for Nuclear Physics. Input into U.S. Long-Range Planning, 2023

Deeply-virtual Compton process e−N→e−γπN to study nucleon to resonance transitions

Coexistence of single particle and collective excitation in 61Ni

Affiliations

The LPM Effect in sequential bremsstrahlung: $1/ N_{c}^{2}$ corrections

Deeply-virtual Compton process $e^{-} N \to e^{-} γ π N$ to study nucleon to resonance transitions

Coexistence of single particle and collective excitation in $^{61}$ Ni