Nuclear Theory·nucl-th

Wednesday·November 13, 2019

12 papers—6 primary·6 cross-listed

07
[Submitted on 11 Nov 2019] (cross-list from hep-ph)
Extracting many-body correlators of saturated gluons with precision from inclusive photon+dijet final states in deeply inelastic scattering
Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸
We highlight the principal results of a computation in the Color Glass Condensate effective field theory (CGC EFT) of the next-to-leading order (NLO) impact factor for inclusive photon+dijet production at Bjorken $x_{Bj} ≪ 1$ in deeply inelastic electron-nucleus (e+A DIS) collisions. When combined with extant results for next-to-leading log $x_{Bj}$ JIMWLK renormalization group (RG) evolution of gauge invariant two-point ("dipole") and four-point ("quadrupole") correlators of light-like Wilson lines, the inclusive photon+dijet e+A DIS cross-section can be determined to $\sim 10$ \% accuracy. Our computation simultaneously provides the ingredients to compute fully inclusive DIS, inclusive photon, inclusive dijet and inclusive photon+jet channels to the same accuracy. This makes feasible quantitative extraction of many-body correlators of saturated gluons and precise determination of the saturation scale $Q_{S, A} (x_{Bj})$ at a future Electron-Ion Collider. An interesting feature of our NLO result is the structure of the violation of the soft gluon theorem in the Regge limit. Another is the appearance in gluon emission of time-like non-global logs which also satisfy JIMWLK RG evolution.
Comments:
8 pages, 4 figures; references added, typo in Eq. 22 corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1911.04519 [pdf]
PRD(2020)·33 citations
08
[Submitted on 11 Nov 2019] (cross-list from hep-ph)
NLO impact factor for inclusive photon $+$ dijet production in $e + A$ DIS at small $x$
Kaushik Roy🇺🇸 · Raju Venugopalan🇺🇸
We compute the next-to-leading order (NLO) impact factor for inclusive photon $+$ dijet production in electron-nucleus (e+A) deeply inelastic scattering (DIS) at small $x$ . An important ingredient in our computation is the simple structure of ``shock wave" fermion and gluon propagators. This allows one to employ standard momentum space Feynman diagram techniques for higher order computations in the Regge limit of fixed $Q^{2} ≫ Λ_{QCD}^{2}$ and $x \to 0$ . Our computations in the Color Glass Condensate (CGC) effective field theory include the resummation of all-twist power corrections $Q_{s}^{2} / Q^{2}$ , where $Q_{s}$ is the saturation scale in the nucleus. We discuss the structure of ultraviolet, collinear and soft divergences in the CGC, and extract the leading logs in $x$ ; the structure of the corresponding rapidity divergences gives a nontrivial first principles derivation of the JIMWLK renormalization group evolution equation for multiparton lightlike Wilson line correlators. Explicit expressions are given for the $x$ -independent $O (α_{s})$ contributions that constitute the NLO impact factor. These results, combined with extant results on NLO JIMWLK evolution, provide the ingredients to compute the inclusive photon $+$ dijet cross-section at small $x$ to $O (α_{s}^{3} ln (x))$ . First results for the NLO impact factor in inclusive dijet production are recovered in the soft photon limit. A byproduct of our computation is the LO photon+ 3 jet (quark-antiquark-gluon) cross-section.
Comments:
104 pages, 35 figures; references added, typo in Eq. 275 corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1911.04530 [pdf]
PRD(2020)·87 citations
09
[Submitted on 11 Nov 2019] (cross-list from hep-th)
Unruh effect universality: emergent conical geometry from density operator
Georgy Y. Prokhorov🇷🇺 · Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺
The Unruh effect has been investigated from the point of view of the quantum statistical Zubarev density operator in space with the Minkowski metric. Quantum corrections of the fourth order in acceleration to the energy-momentum tensor of real and complex scalar fields, and Dirac field are calculated. Both massless and massive fields are considered. The method for regularization of discovered infrared divergences for scalar fields is proposed. The calculated corrections make it possible to substantiate the Unruh effect from the point of view of the statistical approach, and to explicitly show its universality for various quantum field theories of massless and massive fields. The obtained results exactly coincide with the ones obtained earlier by calculation of the vacuum average of energy-momentum tensor in a space with a conical singularity. Thus, the duality of two methods for describing an accelerated medium is substantiated. One may also speak about the emergence of geometry with conical singularity from thermodynamics. In particular, the polynomiality of the energy-momentum tensor and the absence of higher-order corrections in acceleration can be explicitly demonstrated.
Comments:
26 pages, 1 figure
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1911.04545 [pdf]
JHEP(2020)·36 citations
10
[Submitted on 11 Nov 2019] (cross-list from hep-th)
Calculation of acceleration effects using the Zubarev density operator
Georgy Y. Prokhorov🇷🇺 · Oleg V. Teryaev🇷🇺 · Valentin I. Zakharov🇷🇺
The relativistic form of the Zubarev density operator can be used to study quantum effects associated with acceleration of the medium. In particular, it was recently shown that the calculation of perturbative corrections in acceleration based on the Zubarev density operator makes it possible to show the existence of Unruh effect. In this paper, we present the details of the calculation of quantum correlators arising in the fourth order of the perturbation theory needed to demonstrate the Unruh effect. Expressions for the quantum corrections for massive fermions are also obtained.
Comments:
14 pages
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
1911.04563 [pdf]
Particles(2020)·15 citations
11
[Submitted on 12 Nov 2019] (cross-list from hep-ph)
Pion Beta Decay and CKM Unitarity
Andrzej Czarnecki🇨🇦 · William J. Marciano🇺🇸 · Alberto Sirlin🇺🇸
Pion beta decay, $π^{+} \to π^{0} e^{+} ν (γ)$ , provides a theoretically clean $\pm 0.3%$ determination of the CKM matrix element $V_{ud}$ . That value falls short of super-allowed nuclear beta decays where an order of magnitude better precision already exists. We advocate a new strategy for utilizing pion beta decay, based on its role in determining $V_{us} / V_{ud}$ via the ratio $R_{V} = Γ (K \to π l ν (γ)) /Γ (π^{+} \to π^{0} e^{+} ν (γ))$ . $R_{V}$ measures $f_{+}^{K} (0) ∣ V_{us} ∣/ f_{+}^{π} (0) ∣ V_{ud} ∣$ and is insensitive to the Fermi constant and some radiative corrections. Its dependence on the ratio of form factors may also prove useful for lattice gauge theory calculations. Employing a lattice based value $f_{+}^{K} (0) / f_{+}^{π} (0) = 0.970 (2)$ , we find $V_{us} / V_{ud} = 0.22918 (88)$ compared to $V_{us} / V_{ud} = 0.23131 (45)$ obtained from $R_{A} = Γ (K \to μν (γ)) /Γ (π \to μν (γ))$ . Those vector and axial-vector based $V_{us} / V_{ud}$ values exhibit a 2.2 $σ$ discrepancy. That tension may be relieved by a shift in the lattice $f_{+}^{K} (0) / f_{+}^{π} (0)$ towards the consistency range 0.961(4), changes in experimental input or new physics. Other implications of $R_{V}$ and $R_{A}$ are also discussed.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1911.04685 [pdf]
PRD(2020)·55 citations
12
[Submitted on 12 Nov 2019] (cross-list from hep-ph)
Energy density at kinetic freeze-out in Pb-Pb collisions at the LHC using the Tsallis distribution
M. D. Azmi🇮🇳 · T. Bhattacharyya🇷🇺 · J. Cleymans🇿🇦 · M. Paradza🇿🇦
The thermodynamic parameters like energy density, pressure, entropy density, temperature and particle density are determined from the transverse momentum distributions of charged particles in Pb-Pb collisions at the LHC. The results show a clear increase with the centrality and the beam energy in all parameters. It is determined that in the final freeze-out stage the energy density reaches a value of about 0.039 GeV/fm $^{3}$ for the most central collisions at $s_{N N}$ = 5.02 TeV. This is less than that at chemical freeze-out where the energy density is about 0.36 GeV/fm $^{3}$ . This decrease approximately follows a $T^{4}$ law. The results for the pressure and entropy density are also presented for each centrality class at $s_{N N}$ = 2.76 and 5.02 TeV.
Comments:
12 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1911.04878 [pdf]
J.Phys.G(2020)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Extracting many-body correlators of saturated gluons with precision from inclusive photon+dijet final states in deeply inelastic scattering

NLO impact factor for inclusive photon+dijet production in e+A DIS at small x

Unruh effect universality: emergent conical geometry from density operator

Calculation of acceleration effects using the Zubarev density operator

Pion Beta Decay and CKM Unitarity

Energy density at kinetic freeze-out in Pb-Pb collisions at the LHC using the Tsallis distribution

Affiliations

NLO impact factor for inclusive photon $+$ dijet production in $e + A$ DIS at small $x$