Nuclear Theory·nucl-th

Monday·April 19, 2021

10 papers—6 primary·4 cross-listed

07
[Submitted on 15 Apr 2021] (cross-list from hep-ph)
Global Analysis of Leptophilic Z' Bosons
Andrzej J. Buras🇩🇪 · Andreas Crivellin🇨🇭 · Fiona Kirk🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marc Montull🇨🇭
New neutral heavy gauge bosons ( $Z^{'}$ ) are predicted within many extensions of the Standard Model. While in case they couple to quarks the LHC bounds are very stringent, leptophilic $Z^{'}$ bosons (even with sizable couplings) can be much lighter and therefore lead to interesting quantum effects in precision observables (like $(g - 2)_{μ}$ ) and generate flavour violating decays of charged leptons. In particular, $ℓ \to ℓ^{'} ν ν ˉ$ decays, anomalous magnetic moments of charged leptons, $ℓ \to ℓ^{'} γ$ and $ℓ \to 3 ℓ^{'}$ decays place stringent limits on leptophilic $Z^{'}$ bosons. Furthermore, in case of mixing $Z^{'}$ with the SM $Z$ , $Z$ pole observables are affected. In light of these many observables we perform a global fit to leptophilic $Z^{'}$ models with the main goal of finding the bounds for the $Z^{'}$ couplings to leptons. To this end we consider a number of scenarios for these couplings. While in generic scenarios correlations are weak, this changes once additional constraints on the couplings are imposed. In particular, if one considers an $L_{μ} - L_{τ}$ symmetry broken only by left-handed rotations, or considers the case of $τ - μ$ couplings only. In the latter setup, on can explain the $(g - 2)_{μ}$ anomaly and the hint for lepton flavour universality violation in $τ \to μν ν ˉ / τ \to e ν ν ˉ$ without violating bounds from electroweak precision observables.
Comments:
48 pages, 17 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2104.07680 [pdf]
JHEP(2021)·82 citations
08
[Submitted on 13 Apr 2021] (cross-list from physics.data-an)
Efficiency corrections for mutually inclusive variables and particle identification effect for mixed-cumulants in heavy-ion collisions
Arghya Chatterjee🇨🇳 · Toshihiro Nonaka🇯🇵 · ShinIchi Esumi🇯🇵 · Xiaofeng Luo🇨🇳
Mix-cumulants of conserved charge distributions are sensitive observables for probing properties of the QCD medium and phase transition in heavy-ion collisions. To perform precise measurements, efficiency correction is one of the most important step. In this study, using the binomial efficiency model, we derive efficiency correction formulas for mutually exclusive and inclusive variables. The UrQMD model is applied to verify the validity of these formulas for different types of correlations. Furthermore, we investigate the effect of the multiplicity loss and contamination emerging from the particle identifications. This study provides an important step toward future measurements of mixed-cumulants in relativistic heavy-ion collisions.
Comments:
11 pages, 7 figures
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); Nuclear Theory (nucl-th)
arXiv:
2104.08077 [pdf]
CPC(2021)·2 citations
09
[Submitted on 16 Apr 2021] (cross-list from hep-ph)
Collective flow in single-hit QCD kinetic theory
Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇨🇭 · Robin Törnkvist🇸🇪
Motivated by recent interest in collectivity in small systems, we calculate the harmonic flow response to initial geometry deformations within weakly coupled QCD kinetic theory using the first correction to the free-streaming background. We derive a parametric scaling formula that relates harmonic flow in systems of different sizes and different generic initial gluon distributions. We comment on similarities and differences between the full QCD effective kinetic theory and the toy models used previously. Finally we calculate the centrality dependence of the integrated elliptic flow $v_{2}$ in oxygen-oxygen, proton-lead and proton-proton collision systems.
Comments:
Published version. The following changes has been made: updated discussion in section 3.1 and plots of elliptic flow scaling. Added plots for triangular flow scaling. Revised section 3.3 with an improved procedure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2104.08179 [pdf]
JHEP(2021)·38 citations
10
[Submitted on 16 Apr 2021] (cross-list from quant-ph)
Calculation of generating function in many-body systems with quantum computers: technical challenges and use in hybrid quantum-classical methods
Edgar Andres Ruiz Guzman🇫🇷 · Denis Lacroix🇫🇷
The generating function of a Hamiltonian $H$ is defined as $F (t) = ⟨ e^{- i t H} ⟩$ , where $t$ is the time and where the expectation value is taken on a given initial quantum state. This function gives access to the different moments of the Hamiltonian $⟨ H^{K} ⟩$ at various orders $K$ . The real and imaginary parts of $F (t)$ can be respectively evaluated on quantum computers using one extra ancillary qubit with a set of measurement for each value of the time $t$ . The low cost in terms of qubits renders it very attractive in the near term period where the number of qubits is limited. Assuming that the generating function can be precisely computed using quantum devices, we show how the information content of this function can be used a posteriori on classical computers to solve quantum many-body problems. Several methods of classical post-processing are illustrated with the aim to predict approximate ground or excited state energies and/or approximate long-time evolutions. This post-processing can be achieved using methods based on the Krylov space and/or on the $t$ -expansion approach that is closely related to the imaginary time evolution. Hybrid quantum-classical calculations are illustrated in many-body interacting systems using the pairing and Fermi-Hubbard models.
Comments:
15 figures, 10 pages, article original title "Predicting ground state, excited states and long-time evolution of many-body systems from short-time evolution on a quantum computer"
Subjects:
Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
2104.08181 [pdf]
18 citations

Affiliations

first authorsco-authorsvia INSPIRE

Global Analysis of Leptophilic Z' Bosons

Efficiency corrections for mutually inclusive variables and particle identification effect for mixed-cumulants in heavy-ion collisions

Collective flow in single-hit QCD kinetic theory

Calculation of generating function in many-body systems with quantum computers: technical challenges and use in hybrid quantum-classical methods

Affiliations