High Energy Physics - Phenomenology (hep-ph)

Abstract: We study the effect of an ultra-light primordial black hole (PBH) dominated phase on the gravitational wave (GW) spectrum generated by a cosmic string (CS) network formed as a result of a high-scale $U(1)$ symmetry breaking. A PBH-dominated phase leads to tilts in the spectrum via entropy dilution and generates a new GW spectrum from PBH density fluctuations, detectable at ongoing and planned near-future GW detectors. The combined spectrum has a unique shape with a plateau, a sharp tilted peak over the plateau, and a characteristic fall-off, which can be distinguished from the one generated in the combination of CS and any other matter domination or new exotic physics. We discuss how ongoing and planned future experiments can probe such a unique spectrum for different values of $U(1)$ breaking scale and PBH parameters such as initial mass and energy fraction.

Abstract: We study $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' l \bar\nu$ and $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' \nu \bar\nu$ decays with all low lying octet and decuplet baryons using a topological amplitude approach. In tree induced $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' l \bar\nu$ decay modes, we need 2 tree and 1 annihilation amplitudes in octet-anti-octet decay modes, 1 tree amplitude in octet-anti-decuplet decay modes, 1 tree amplitude in decuplet-anti-octet decay modes and 1 tree and 1 annihilation amplitudes in decuplet-anti-decuplet decay modes. In loop induced $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' \nu \bar\nu$ decay modes, similar numbers of penguin-box and penguin-box-annihilation amplitudes are needed. Relations on these semileptonic baryonic $B_q$ decay amplitudes are found. Furthermore, the ratios of loop topological amplitudes and tree topological amplitudes are fixed by known CKM factors and loop functions. The observed $B^-\to p\bar p \mu^-\bar\nu$ differential rate exhibits threshold enhancement, which is expected to hold in all other semileptonic baryonic modes. The threshold enhancement squeezes the phase space and leads to very large SU(3) breaking effects in the decay rates. They are estimated using the measured $B^-\to p\bar p \mu^-\bar\nu$ differential rate and model calculations. Modes with relatively unsuppressed rates and good detectability are identified. These modes can be searched experimentally in near future and the rate estimations can be improved when more modes are discovered. Ratios of rates of some loop induced $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' \nu \bar\nu$ decays and tree induced $\bar B_q\to {{\rm\bf B}\bar{\rm\bf B}}' l \bar\nu$ decays are predicted and can be checked experimentally. They can be tests of the SM.

Abstract: In this talk, an alternative to top partner solutions and its consequences on phenomenology are discussed. The hierarchy problem from the top loop contribution is solved by mitigating the top Yukawa coupling at high scales. In this scenario, the new degrees of freedom appearing at the cut-off scale of the top loop should then be some new top-philic particles instead of traditional top partners. The idea can be directly tested through measurements in top physics, including $t\bar{t}h$, $t\bar{t}$ differential cross section, and $t\bar{t}t\bar{t}$ cross section.

Abstract: I consider the frame dependence of QCD bound states in the presence of a confining, spatially constant gluon field energy density. The states are quantized at equal time in $A^0=0$ (temporal) gauge. I derive the frame dependence of the wave functions, and demonstrate the Lorentz covariance of the electromagnetic (transition) form factors for states of any spin. The wave functions of $J^{PC}=0^{-+}$ states with CM momentum $P \neq 0$ are considered in some detail, verifying their local normalizability and the expected frame dependence of the bound state energy.

Abstract: We investigate, in addition to the experimentally established hadrons, how the inclusion of extra resonance states, through the Hagedorn mass spectrum (HS) or Quark Model (QM) predicated states, affects the thermodynamic and transport quantities of the hadronic system in the van der Waals hadron resonance gas (VDWHRG) model. We found that the VDWHRG model with the HS provides the most accurate description of the lattice QCD results, both at zero and finite chemical potential. Moreover, the inclusion of these extra states has a significant impact on the van der Waals (VDW) parameters, which, in turn, affect the thermodynamic and transport quantities as well as the likely position of the liquid-gas phase transition critical point in the QCD phase diagram. Additionally, we infer that there is a strong correlation between the van der Waals parameters and the chemical potential. Overall, our study sheds light on the importance of considering extra resonance states and proper tuning of the VDW parameters in the VDWHRG model to enhance the accuracy and reliability of the model in the context of Ultra-relativistic heavy-ion physics.

Abstract: Due to the greater experimental precision expected from the currently ongoing LHC Run 3, equally accurate theoretical predictions are essential. We update the documentation of the Resummino package, a program dedicated to precision cross section calculations for the production of a pair of sleptons, electroweakinos, and leptons in the presence of extra gauge bosons, and for the production of an associated electroweakino-squark or electroweakino-gluino pair. We detail different additions that have been released since the initial version of the program a decade ago, and then use the code to investigate the impact of threshold resummation corrections at the next-to-next-to-leading-logarithmic accuracy. As an illustration of the code we consider the production of pairs of electroweakinos and sleptons at the LHC for centre-of-mass energies ranging up to 13.6 TeV and in simplified model scenarios. We find slightly increased total cross section values, accompanied by a significant decrease of the associated theoretical uncertainties. Furthermore, we explore the dependence of the results on the squark masses.

Abstract: In this work, a modified NJL-type model is used, in which the contact current-current interaction is Fierz-transformed into quark-antiquark interactions $\mathcal{F}_{\bar{q} q}=(\bar{q} \hat{O} q)^{2}$ and quark-quark interactions $\mathcal{F}_{q q}=(q \hat{O} q)^{2}$, which are directly related to the chiral condensate and diquark condensate, respectively. Under mean-field approximation, the chiral condensate and the diquark condensate are studied on the same footing. We discuss in detail the competition between the chiral condensate and the diquark condensate, as well as the order of the chiral phase transition by analyzing the resulting chiral susceptibility.

Abstract: In this study, we investigate the nonleptonic decays of heavy baryons \Xi^0_c induced by the c\to u (d \bar{d})/ (s \bar{s}) transition. Utilizing the factorization assumption, hadronic form factors are calculated within the light-front quark model. We employ helicity amplitudes to analyze the nonleptonic decay modes of heavy baryons and derive benchmark results for partial decay widths and branching fractions. Our calculations suggest that the branching fractions for some of these rare nonleptonic decays are at the order of 10^ {-5} or 10^ {-6}, which are likely to be detectable at experiments such as LHCb or Belle-II. The potential data accumulated in the future may help to further our understanding of the decay mechanism in the presence of heavy quarks.