High Energy Physics - Phenomenology (hep-ph)

Abstract: Linear response approach to the relativistic coupled-cluster (RCC) theory has been extended to estimate contributions from the parity and time-reversal violating pseudoscalar-scalar (Ps-S) and scalar-pseudoscalar (S-Ps) electron-nucleus interactions along with electric dipole moments (EDMs) of electrons ($d_e$) interacting with internal electric and magnetic fields. Random phase approximation (RPA) is also employed to produce results to compare with the earlier reported values and demonstrate importance of the non-RPA contributions arising through the RCC method. It shows that contributions from the S-Ps interactions and $d_e$ arising through the hyperfine-induced effects are very sensitive to the contributions from the high-lying virtual orbitals. Combining atomic results with the nuclear shell-model calculations, we impose constraints on the pion-nucleon coupling coefficients, and EDMs of proton and neutron. These results are further used to constrain EDMs and chromo-EDMs of up- and down-quarks by analyzing particle physics models.

Abstract: The axial-vector form factors of the light, singly and doubly charmed baryons are investigated in the framework of $SU(4)$ chiral constituent quark model. The axial-vector form factors having physical significance correspond to the generators of the $SU(4)$ group with flavor singlet $\lambda^{0}$, flavor isovector $\lambda^{3}$, flavor hypercharge $\lambda^{8}$ and flavor charmed $\lambda^{15}$ combinations of axial-vector current at zero momentum transfer. In order to further understand the $Q^2$ dependence of these charges, we have used the conventionally established dipole form of parametrization.

Abstract: We study the azimuthal asymmetries in back-to-back leptoproduction of $D$-meson and jet to probe the gluon TMDs in an unpolarized and transversely polarized electron-proton collision at the kinematics of EIC. We give predictions for unpolarized cross-sections within the TMD factorization framework. In $D$-meson and jet formation, the only leading order contribution comes from the photon gluon fusion process. We give numerical estimates of the upper bound on the azimuthal asymmetries with the saturation of positivity bounds; also, we present the asymmetries using a Gaussian parameterization of TMDs. We obtain sizable asymmetries in the kinematics that will be accessible at EIC.

Abstract: We propose a minimal extension of the Standard Model by incorporating sterile neutrinos and a QCD axion to account for the mass and mixing hierarchies of quarks and leptons and to solve the strong CP problem, and by introducing $G_{\rm SM}\times \Gamma_N\times U(1)_X$ symmetry. We demonstrate that the K{\"a}hler transformation corrects the weight of modular forms in the superpotential and show that the model is consistent with the modular and $U(1)_X$ anomaly-free conditions. This enables a simple construction of a modular-independent superpotential for scalar potential. Using minimal supermultiplets, we demonstrate a level 3 modular form-induced superpotential. Sterile neutrinos explain small active neutrino masses via the seesaw mechanism and provide a well-motivated $U(1)_X$ breaking scale, whereas gauge singlet scalar fields play crucial roles in generating the QCD axion, heavy neutrino mass, and fermion mass hierarchy. The model predicts a range for the $U(1)_X$ breaking scale from $10^{13}$ GeV to $10^{15}$ GeV for $1\,\mbox{TeV}< m_{3/2}<10^6\,\mbox{TeV}$. In the supersymmetric limit, all Yukawa coefficients in the superpotential are given by complex numbers with an absolute value of unity, implying a democratic distribution. Performing numerical analysis, we study how model parameters are constrained by current experimental results. In particular, the model predicts that the value of the quark Dirac CP phase falls between $38^\circ$ to $87^\circ$, which is consistent with experimental data, and the favored value of the neutrino Dirac CP phase is around $250^\circ$. Furthermore, the model can be tested by ongoing and future experiments on axion searches, neutrino oscillations, and $0\nu\beta\beta$-decay.

Abstract: We consider pion condensation in cold and dense QCD using chiral perturbation theory ($\chi$PT). Thermodynamic quantities are calculated at next-to-leading order in the low-energy expansion. In the nonrelatistivtic limit, we recover the classic result by Lee and Yang for the energy density of a dilute Bose gas with an $s$-wave scattering length that includes loop corrections from $\chi$PT. In the chiral limit, we calculate the thermodynamic functions to next-to-leading order in the low-energy expansion. We use Son's prescription to write down an effective field theory for the massless Goldstone boson that results from the spontaneous breakdown of the global internal symmetry $U(1)_{I_3}$ at finite isospin density $n_I$. In the ultrarelativistic limit, the phonons propagate with the speed of light up to renormalization effects. The damping rate of the phonons behaves as $p^5$ for small momenta in agreement with Beliaev's old result for a weakly interacting Bose gas.

Abstract: Axion dark matter is converted to electromagnetic radiations in the presence of strong magnetic field. The radiations possibly give rise to non trivial phenomena in condensed matter physics. Especially, we discuss that saturation of plateau-plateau transition width observed at low temperature in integer quantum Hall effect is caused by the axion. The radiations from axions are inevitably present in the experiment. Although the radiations generated by axion is extremely weak, Hall conductivity jumps up to next plateau even if only a single electron occupies an extended state; a localized electron is transited to the extended state by absorbing the radiation. According to our analysis, previous experiment\cite{sat6} of the saturation in detail suggests that the axion mass is in the range $10^{-5}\mbox{eV}\sim 10^{-6}$eV. We propose a way of the determination of the axion mass by imposing microwaves on Hall bar and also a way of the confirmation that the axion really causes the saturation of the width.

Abstract: The spin-$\nicefrac{3}{2}$ to spin-$\nicefrac{1}{2}$ doubly heavy baryon transition magnetic dipole $G_M$ and electric quadrupole $G_E$ formfactors are calculated in the framework of light cone sum rules method. Moreover, the decay widths of corresponding radiative transitions are estimated. Obtained results of magnetic dipole moments $G_M$ and decay widths are compared with the results present in the literature.

Abstract: Radiative corrections are crucial for modern high-precision physics experiments, and are an area of active research in the experimental and theoretical community. Here we provide an overview of the state of the field of radiative corrections with a focus on several topics: lepton-proton scattering, QED corrections in deep-inelastic scattering, and in radiative light-hadron decays. Particular emphasis is placed on the two-photon exchange, believed to be responsible for the proton form-factor discrepancy, and associated Monte-Carlo codes. We encourage the community to continue developing theoretical techniques to treat radiative corrections, and perform experimental tests of these corrections.

Abstract: The discrete symmetry $Z_4$ in the standard model (SM) with three right-handed neutrinos is free from the Dai-Freed anomaly. Motivated by this $Z_4$ symmetry, we constructed a topological inflation model consistent with all known constraints and observations. However, we assumed a specific inflaton potential in the previous work. In this paper we extend the inflaton potential in a more general form allowed by the discrete $Z_4$ gauge symmetry and show that consistent hilltop inflation is realized. We find that the Hubble parameter $H_\mathrm{inf}$ can be smaller than $\simeq 10^{9}$ GeV so that the isocurvature fluctuations of the axion dark matter are sufficiently suppressed. Furthermore, the running of the spectral index can be as large as $dn_s/\ln k \simeq 0.0018$ which will be tested in future CMB observations. Since this discrete $Z_4$ acts on the SM, the inflaton can couple to pairs of the right-handed neutrinos and hence the reheating temperature can be high as $\sim 10^{10}$ GeV, producing the cosmic baryon asymmetry naturally through the thermal leptogenesis.

Abstract: This is a doctoral thesis dissertation developed in the frame of theoretical QCD predictions, with focus on two main topics. On the one hand, the large-order bahavior of perturbative QCD series is discussed. By reviewing the main literature, a cohesive discussion is made that includes the topics of large-order divergencies in QCD, renormalons, summation methods for asymptotic series and non-perturbative power corrections. A formalism for perturbative QCD series in the large-$\beta_0$ is presented, which allows for (1) the computation of the series, its renormalization factor and anomalous dimension, (2) the sum of all these quantities, (3) the study of the renormalon structure of the series and (4), the ambiguity in the sum due to IR renormalons, which is associated with the size of non-power corrections. Original and published work has been made to develop this formalism for both series without and with cusp-anomalous dimension. A large number of applications of our formalism are also presented, covering the short-distance mass schemes $\bar{\rm MS}$ and MSR, the QCD-to-SCET and SCET-to-bHQET matching coeficients and the SCET and bHQET jet functions. On the other hand, original and also published work in fixed-order perturbation theory is also carried out in the field of event shapes. The event-shape distribution for $e^+e^-$ to hadrons is computed to NLO differential with respect to the angle between the initial beam and the thrust axis of the event. The relevant finding is the presence of the quark mass already at $\cal{O}(\alpha_s^0)$ for the vector current. Finally, the dissertation also contains a brief study on the FOPT-CIPT difference in the context of tau decays.

Abstract: Using the PDG 22 compilation of the $e^+e^-\to$ Hadrons data $\oplus$ the recent CMD3 data for the pion form factor and the value of gluon condensate $\langle\alpha_s G^2\rangle$ from heavy quarkonia, we extract the value of the four-quark condensate: $\rho\alpha_s\langle\bar\psi\psi\rangle^2= (5.9\pm 0.4)\times 10^{-4}$ GeV$^6$ from the ratio ${\cal R}_{10}$ of Laplace sum rules. We also show the inconsistency in using at the same time the standard SVZ value of the gluon and the vacuum saturation of the four-quark condensates. The dimension eight condensate is found to be\,: $d_8= (11.3\pm 1.1)\times 10^{-2}$ GeV$^8$. Using the previous QCD condensates, we extract from the lowest $\tau$-like decay moment ${\cal R}_\tau^{ee}$ the value of the QCD coupling\,: $\alpha_s(M^2_\tau)=0.329(10)$ within fixed order perturbation theory (FO) and the standard Operator Product Expansion (OPE). The corresponding value of the sum of the non-perturbative contribution is\,: $\delta_{NP}(M_\tau)=(2.32\pm 0.15)\times 10^{-2}$. Reciprocically, using $\alpha_s(M_\tau)$, $\alpha_s G^2$ and $d_8$ as inputs, we test the stability of the value of the four-quark condensate obtained from the lowest $\tau$-like moment. We complete our analysis by updating our previous determinations of the lowest order hadronic vacuum polarization contributions to the lepton anomalies and to $\alpha(M^2_Z)$. We obtain in Table\,\ref{tab:amu1}: $a_\mu\vert^{hvp}_{l.o}= (7036.5\pm 38.9)\times10^{-11}, \, a_\tau\vert^{hvp}_{l.o}= (3494.8\pm 24.7)\times10^{-9} $. and $\alpha(M^2_Z)=(2766.3\pm 4.5)\times 10^{-5}$. This new value of $a_\mu$ leads to : $\Delta a_\mu\equiv a_\mu^{exp}-a_\mu^{th} = (142\pm 42_{th}\pm 41_{exp})\times 10^{-11}$. which reduces the tension between the SM prediction and experiment.

Abstract: We investigate the differences between the light-cone distribution amplitudes (LCDAs) of $B_s$ mesons and $B_q$ mesons (with $q=u,d$) induced by a non-vanishing strange-quark mass $m_s\neq 0$ (compared to $m_q \simeq 0$). To this end, we consider the so-called ''radiative tail'' which is related to the short-distance expansion of the relevant light-ray operators in heavy-quark effective theory. We extend the calculation of the according matching coefficients, including operators linear in $m_s$ for both the leading and sub-leading 2-particle LCDAs. Based on a generic parameterization for the leading LCDA, we discuss the effect on its shape on a quantitative level, and compare our findings with recent results on the inverse moments of the $B_q$ and $B_s$ LCDAs from QCD sum rules.

Abstract: Recent advancements in charmoniumlike state have significantly enriched the discovery of new hadronic states, providing exciting opportunities for further investigations into the fascinating realm of charmonium physics. In this letter, we focus on the vector charmonium family and perform a detailed analysis of the recently observed $e^+e^-\to \pi^+ D^0 D^{*-}$ process. Our findings demonstrate a striking agreement between the observed peak structures and the predicted characterized energy level structure of higher vector charmonia including the $\psi(4220)$, $\psi(4380)$, $\psi(4415)$, and $\psi(4500)$, which are derived from an unquenched potential model. This discovery challenges conventional understanding of higher charmonia above 4 GeV and offers fresh insights into the dynamics of charm and anti-charm quarks in the formation of these states. Furthermore, the identification of these higher charmonia in the precisely measured $\pi^+ D^0D^{*-}$ open-charm decay channel would serve as compelling evidence supporting the unquenched scenario and contribute to a deeper understanding of the nonperturbative aspects of the strong interaction.

Abstract: We consider quantum-decoherence effects in neutrino oscillation data. Working in the open quantum system framework we adopt a phenomenological approach that allows to parameterize the energy dependence of the decoherence effects. We consider several phenomenological models. We analyze data from the reactor experiments RENO, Daya Bay and KamLAND and from the accelerator experiments NOvA, MINOS/MINOS+ and T2K. We obtain updated constraints on the decoherence parameters quantifying the strength of damping effects, which can be as low as $\Gamma_{ij} \lesssim 8 \times 10^{-27}$ GeV at 90% confidence level in some cases. We also present sensitivities for the future facilities DUNE and JUNO.

Abstract: In R-parity-violating (RPV) supersymmetric models, light neutralinos with masses from the GeV-scale down to even zero are still allowed by all laboratory constraints. They are further consistent with dark matter observations, as they decay via RPV couplings. These RPV couplings are in general constrained to be small. Hence, such light neutralinos, if produced, e.g., at a beam-dump or collider experiment, appear as displaced vertices or missing energy at the detector level. The same signatures have been extensively searched for at various experiments in the theoretical context of sterile neutrinos which mix with active neutrinos. In this work, we recast the sensitivity of both past and present experiments to sterile neutrinos to obtain new bounds on RPV couplings associated with a light neutralino. We find experiments such as T2K, BEBC, FASER, DUNE, and MoEDAL-MAPP can improve the current bounds on RPV couplings by up to $3-4$ orders of magnitude in several benchmark scenarios.

Abstract: We investigate the implications of decoherence induced by quantum spacetime properties on neutrino oscillation phenomena. We develop a general formalism where the evolution of neutrinos is governed by a Lindblad-type equation and we compute the oscillation damping factor for various models that have been proposed in the literature. Furthermore, we discuss the sensitivity to these effects of different types of neutrino oscillation experiments, encompassing astrophysical, atmospheric, solar, and reactor neutrino experiments. By using neutrino oscillation data from long-baseline reactors and atmospheric neutrino observations, we establish stringent constraints on the energy scale governing the strength of the decoherence induced by stochastic metric fluctuations, amounting to, respectively, $E_{QG}\geq 4.1 \cdot 10^{24}\; \text{GeV}$ and $E_{QG}\geq 4.2\cdot 10^{34}\;\text{GeV}$.

Abstract: The QCD coupling, $\alpha_s$, has a critical role in Hadron collider studies of the Standard Model Effective Field Theory (SMEFT). Patterns of measurements can be modified by local contact operators in the SMEFT that change the measured value of a Lagrangian parameter from the case of the Standard Model; this is known as an input parameter correction. When such a parameter is then used to predict another observable, this modifies the relationship between observables. In this paper, we begin the process of characterizing $\alpha_s$ as an input parameter.

Abstract: We narrate dark matter, neutrino magnetic moment and mass in a Type-III radiative scenario. The Standard Model is enriched with three vector-like fermion triplets and two inert doublets to provide a suitable platform for the above phenomenological aspects. The inert scalars contribute to total relic density of dark matter in the Universe. Neutrino aspects are realized at one-loop with magnetic moment obtained through charged scalars, while neutrino mass gets contribution from charged and neutral scalars. Taking inert scalars up to $2$ TeV and triplet fermion in few hundred TeV range, we obtain a common parameter space, compatible with experimental limits associated with both neutrino and dark matter sectors. Using a specific region for transition magnetic moment (${\cal O} (10^{-11}\mu_B$)), we explain the excess recoil events, reported by the XENON1T collaboration.

Abstract: We formulate the coupling between fermion spin and background electromagnetic fields using form factors. We show that the vacuum form factors at tree level reproduce the spin polarization effects found in chiral kinetic theory. The vacuum form factors corresponding to spin couplings to perpendicular electric field, parallel and perpendicular magnetic field are degenerate. The degeneracy is expected to be lifted in medium. As an example, we calculate the in-medium QCD radiative correction to the form factors at one-loop order, where we find partial lift of the degeneracy: the spin couplings to parallel and perpendicular magnetic field are different, but the spin couplings to perpendicular electric and parallel magnetic field remain the same.

Abstract: In recent years, several pulsar timing array collaborations have reported first hints for a stochastic gravitational wave background at nano-Hertz frequencies. Here we elaborate on the possibility that this signal comes from new physics that leads to the generation of a primordial stochastic gravitational wave background. We propose a set of simple but concrete models that can serve as benchmarks for gravitational waves sourced by cosmological phase transitions, domain wall networks, cosmic strings, axion dynamics, or large scalar fluctuations. These models are then confronted with pulsar timing data and with cosmological constraints. With only a limited number of free parameters per model, we are able to identify viable regions of parameter space and also make predictions for future astrophysical and laboratory tests that can help with model identification and discrimination.

Abstract: We examine the ability of experimental measurements of top-quark pair production to constrain both the top-quark mass and the strong coupling within the global MSHT parton distribution function (PDF) fit. Specifically, we consider ATLAS and CMS measurements of differential distributions taken at a centre-of-mass energy of 8 TeV, as well as $t\bar{t}$ total cross section data taken at a variety of experiments, and compare to theoretical predictions including next-to-next-to-leading order corrections. We find that supplementing the global fit with this additional information results in relatively strong constraints on the top-quark mass, and is also able to bound the strong coupling in a limited fashion. Our final result is $m_t=173.0\pm0.6~\mathrm{GeV}$ and is compatible with the world average pole mass extracted from cross section measurements of $172.5\pm0.7~\mathrm{GeV}$ by the Particle Data Group. We also study the effect of different top-quark masses on the gluon parton distribution function, finding changes at high $x$ which nonetheless lie within the large PDF uncertainties in this region.