High Energy Physics - Phenomenology (hep-ph)

Abstract: We investigate the chiral anomaly in a Floquet system under a time-periodic electric field in (1+1) dimensions. Using the van~Vleck high-frequency expansion, we analytically quantify how the topological charge is equated with the chirality production and the pseudo-scalar condensate for massive fermions. In the high-frequency limit, we find that finite-mass effects are suppressed and the topological charge is dominated by the chirality production. Our calculations show that the information about the chiral anomaly is stored not in the static Floquet Hamiltonian but in the periodic kick operator. The computational steps are useful as the theoretical foundation for higher-dimensional generalization.

Abstract: We investigate the neutral-current neutrino-nucleon deep inelastic scattering with particular emphasis on short-range correlation and EMC effect, as well as their impact on the weak-mixing angle $\sin^2\theta_W$ determination. The ratios of structure function $F_{2(NC)}^{A}$ and $x F_{3(NC)}^{A}$ are presented where the nuclei $A$ are chosen as carbon, iron and lead. One kind of universal modification function is proposed which would provide a nontrivial test of SRC universality on the platform of neutrino-nucleon DIS. In addition, we study the impact of ``SRC-driven'' nuclear effects on the extraction of $\sin^2\theta_W$ which is naturally associated with the renowned NuTeV anomaly. The results indicate that these effects may account for a substantial fraction of the NuTeV anomaly and considerably affect the value of extracted $\sin^2\theta_W$.

Abstract: This review aims to provide a very short and pedestrian introduction to some of the basics of extra-dimensional physics. The hope is to facilitate access and to be, in some respects, complementary to the many already existing reviews on phenomenological applications of extra dimensions in our Universe.

Abstract: We investigate the survival probability of unstable states, the time-dependence of an initial state, in coupled channels. First, we extend the formulation of the survival probability from single channel to coupled channels (two channels). We derive an exact general expression of the two-channel survival probability using uniformization, a method which makes the coupled-channel S matrix single-valued, and the Mittag-Leffler expansion, i.e. a pole expansion. Second, we calculate the time dependence of the two-channel survival probability by employing the derived expression. It is the minimal distance between the pole and the physical region in the complex energy plane, not the imaginary part of the pole energy, which determines not only the energy spectrum of the Green's function but also the survival probability. The survival probability of the "threshold-cusp" caused by a pole on the unusual complex-energy Riemann sheet is shown to decay, not grow in time though the imaginary part of the pole energy is positive. We also show that the decay of the "threshold-cusp" is non-exponential. Thus, the "threshold-cusp" is shown to be a new type of unstable mode, which is found only in coupled channels.

Abstract: Suggested by Au, Morgan, Pennington (AMP) S-wave isospin I=0 $\pi\pi$, $KK$ scattering amplitude is good enough to describe experimental data for the moment. Still it has two disadvantages for use in multiparticle partial wave analysis (PWA), namely sharp drop at the $KK$ threshold and unreasonable behavior at $M(\pi\pi) > 1.6\,GeV/c^2$. The drop is not seen in multiparticle systems. We suggest the modified AMP amplitude, mAMP, for the only aim, namely to describe the broad part of $S$-wave $\pi\pi\,\to\,\pi\pi$ scattering in the wide $M(\pi\pi)$ range in multiparticle PWA. The mAMP amplitude describes threshold behavior of the $\pi\pi\,\to\,\pi\pi$ scattering and the wide structure at $M\sim 1400\,MeV/c^2$ reasonably well. It is assumed that narrow objects $f_0(980)$, $f_0(1500)$ are included in PWA separately. The amplitude does not describe $\pi\pi\to KK$ scattering. The mAMP amplitude is purely phenomenological.

Abstract: The detection of a heavy neutral CP-even Higgs boson of the $B-L$ Supersymmetric Standard Model (BLSSM), $h'$, with $m_{h'}\simeq 400~\text{GeV}$, at the Large Hadron Collider (LHC) for a center-of-mass energy of $\sqrt{s}=14~\text{TeV}$, is investigated. The following production and decay channels are considered: $gg\to h'\to{ZZ}\to4\ell$ and $gg\to h'\to{W^+W^-}\to2\ell+\slashed{E}_T$ (with $\slashed{E}_T$ being the Missing~Transverse~Energy~(MET)), where $\ell=e,\mu$, with integrated luminosity $L_{\text{int}}=300~{\text{fb}}^{-1}$ (Run 3). Furthermore, we also look into the di-Higgs channel $gg\to h'\to{hh}\to{b\bar{b}\gamma\gamma}$ at the High-Luminosity LHC (HL-LHC) with an integrated luminosity of $L_{\text{int}}=3000~{\text{fb}}^{-1}$. We demonstrate that promising signals with high statistical significance can be obtained through the three aforementioned channels.

Abstract: It has been recently argued that the inclusive hadroproduction at the LHC of a Higgs boson in association with a jet can be sensitive to the high-energy dynamics. Moreover, the impact of the resummation at FCC energies is expected to be large also in the inclusive cross section for the main Higgs production channel in proton-proton collisions, namely the gluon fusion. As the energy increases, a pure $k_t$-factorization framework or a collinear-factorization approach supplemented by the high-energy resummation are adequate formalisms to describe these processes. In both cases, the fundamental missing ingredient for a next-to-leading logarithmic description is the Higgs boson impact factor. We present the full next-to-leading result for the forward Higgs impact factor, obtained in the infinite top-mass limit, discussing possible future extensions, such as the calculation of the impact factor in the central rapidity region.

Abstract: We explore the gravitational wave spectrum generated by string-wall structures in an $SO(10)$ ($Spin(10)$) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs $126$-plet vacuum expectation value (VEV) $\left<126_H\right>$ leaves unbroken the $\mathbb{Z}_2$ subgroup of $\mathbb{Z}_4$, the center of $SO(10)$. Among other things, this yields topologically stable cosmic strings with a string tension $\mu \sim \left<126_H\right>^2$. The subsequent (spontaneous) breaking of $\mathbb{Z}_2$ at a significantly lower scale by the $16$-plet VEV $\left<16_H\right>$ leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for $G \mu$ values varying between $10^{-15}$ and $10^{-9}$ ($\left<126_H\right>\sim 10^{11}$ - $10^{14}$ GeV), and $\left<16_H\right>\sim 0.1$ - $10^3$ TeV range ($G$ denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others.

Abstract: We study the $\bar{B}\to D(D^*) \ell^-\bar{\nu}_{\ell}$ decays based on the up-to-date available inputs from experiments and the lattice. First, we review the standard model (SM) predictions of the different observables associated with these decay channels. In the analyses, we consider new physics (NP) effects in the channels with the heavy ($\tau$), as well as the light leptons ($\mu, e$). We have extracted $|V_{cb}|$ along with the new Wilson coefficients (WCs) from the available data on light leptons; the extracted value of $|V_{cb}|$ is $(39.9 \pm 0.7)\times 10^{-3}$. The extracted WCs are zero consistent, but some could be of order $10^{-2}$. Also, we have done the simultaneous analysis of the data in $\bar{B} \to D^{(*)}(\mu^-,e^-)\bar{\nu}$ alongside the inputs on $R(D^{(*)}) = \frac{\Gamma(\bar{B}\to D^{(*)}\tau^-\bar{\nu}_{\tau})}{\Gamma(\bar{B}\to D^{(*)}\ell^-\bar{\nu}_{\ell})}$ and the $D^*$ longitudinal polarisation fraction $F_L^{D^*}$ in different NP scenarios and extracted $|V_{cb}|$ which is consistent with the number mentioned above. Also, the simultaneous explanation of $R(D^{(*)})$ and $F_L^{D^*}$ is not possible in the one-operator scenarios. However, the two operator scenarios with $\mathcal{O}_{S_2}^{\tau} = (\bar{q}_R b_L)(\bar{\tau}_R\nu_{\tau L})$ as one of the operators could explain all these three measurements. Finally, we have given predictions of all the related observables in $\bar{B} \to D^{(*)}(\tau^-,\mu^-,e^-)\bar{\nu}$ decays in the NP scenarios, which could be tested in future experiments. We have repeated this exercise for $\bar{B} \to \pi\ell^-\bar{\nu}_{\ell}$ decays with the light lepton and extracted $|V_{ub}|$ and the new WCs. Finally, using all these available data for the light and heavy leptons, we have given bounds on the couplings of the relevant SM effective field theory (SMEFT) operators and the probable NP scale $\Lambda$.