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Nuclear Theory·nucl-th

Monday·August 28, 2023

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 05

    MeV Sterile Neutrino in light of the Cabibbo-Angle Anomaly

    Teppei Kitahara🇨🇳 · Kohsaku Tobioka🇺🇸

    A modified neutrino sector could imprint a signature on precision measurements of the quark sector because many such measurements rely on the semi-leptonic decays of the charged currents. Currently, global fits of the determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements point to a -level deficit in the first-row CKM unitarity test, commonly referred to as the Cabibbo-angle anomaly. We find that a MeV sterile neutrino that mixes with the electron-type neutrino increases the extracted , accommodating the Cabibbo-angle anomaly. This MeV sterile neutrino affects the superallowed nuclear decays and neutron decay, but it barely modifies the other measurements of the CKM elements. While various constraints may apply to such a sterile neutrino, we present viable scenarios within an extension of the inverse seesaw model.

    ↳ hep-phhep-exnucl-thPRD(2023)·4 citations
  2. 06

    Exclusive QCD Factorization and Single Transverse Polarization Phenomena at High-Energy Colliders

    Zhite Yu🇺🇸

    This Ph.D.~thesis is divided into two distinct parts. The first part focuses on hard exclusive scattering processes in Quantum Chromodynamics (QCD) at high energies, while the second part delves into spin phenomena at the Large Hadron Collider (LHC). Hard exclusive scattering processes play a crucial role in QCD at high energies, providing unique insights into the confined partonic dynamics within hadrons, complementing inclusive processes. Studying these processes within the QCD factorization approach yields the generalized parton distribution (GPD), a nonperturbative parton correlation function that offers a three-dimensional tomographic parton image within a hadron. However, the experimental measurement of these processes poses significant challenges. This thesis will review the factorization formalism for related processes, examine the limitations of some widely used processes, and introduce two novel processes that enhance the sensitivity to GPD, particularly its dependence on the parton momentum fraction . The second part of the thesis centers on spin phenomena, specifically single spin production, at the LHC. Noting that a single transverse polarization can be generated even in an unpolarized collision, this research proposes two new jet substructure observables: one for boosted top quark jets and another for high-energy gluon jets. The observation of these phenomena paves the way for innovative tools in LHC phenomenology, enabling both precision measurements and the search for new physics.

    ↳ hep-phhep-latnucl-exnucl-th5 citations
  3. 07

    Robust features of QCD phase diagram through a Contact Interaction model for quarks: A view from the effective potential

    Aftab Ahmad🇵🇰 · Muhammad Azher🇵🇰 · Alfredo Raya🇲🇽

    Our research delves into the QCD phase diagram in the temperature and quark chemical potential plane. We use a unique confining contact interaction effective model of quark dynamics that maintains the QCD symmetry intact. By embedding the model into a Schwinger-Dyson equations framework, within a Landau gauge rainbow-ladder-like truncation, we derive the gap equation. In order to accurately regulate the said equation, we utilize the Schwinger optimal time regularization scheme. We further derive the effective potential of the model by integrating the gap equation over the dynamical mass, which along with the confining length scale serve as parameters for the chiral and confinement deconfinement phase transitions, respectively. A cross-over transition is observed at low and above a critical value of the temperature , whilst a first order phase transition is found for low at high density. The critical end point is estimated to be located at , which falls within the range of other QCD effective models predictions. MeV is the critical temperature at vanishing . Screening effects of the medium which dilute the strength of the effective coupling are considered by including the vacuum polarization contribution due to quarks at high temperatures into the framework. It locates the critical end point at , which hints for a deeper analysis of screening effects on models of this kind.

    ↳ hep-phnucl-thEPJA(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE