New articles on High Energy Physics - Phenomenology

[1] 2306.04671

Higgs Inflation and the Electroweak Gauge Sector

We introduce a new method that allows for the Higgs to be the inflaton. That is, we let the Higgs be a pseudo-Nambu-Goldstone (pNG) boson of a global coset symmetry $G/H$ that spontaneously breaks at an energy scale $\sim 4\pi f$ and give it a suitable $SU(2) \subset G$ Chern-Simons interaction, with $\beta$ the dimensionless Chern-Simons coupling strength and $f$ an $SU(2)$ decay constant. As a result, slow-roll inflation occurs via $SU(2)$-induced friction down a steep sinusoidal potential. In order to obey electroweak $SU(2)_{\rm L}\times U(1)_Y$ symmetry, the lowest-order Chern-Simons interaction is required to be quadratic in the Higgs with coupling strength $\propto \beta^2/f^2$. Higher-order interaction terms keep the full Lagrangian nearly invariant under the approximate pNG shift symmetry. Employing the simplest symmetry coset $SU(5)/SO(5)$, $N$ $e$-folds of inflation occur when $N \approx 60 \left(g/0.64\right)^2\left[\beta/\left(3\times 10^6\right)\right]^{8/3}\left[f/\left(5\times 10^{11}\ {\rm GeV}\right)\right]^{2/3}$, with $g$ the weak isospin gauge coupling constant. Small values of the decay constant, $f \lesssim 5 \times 10^{11} {\rm GeV}$, which are needed to address the Higgs hierarchy problem, are ruled out by electric dipole measurements and so successfully explaining inflation requires large $\beta$. We discuss possible methods to achieve such large couplings and other alternative Higgs inflation scenarios outside the standard modified-gravity framework.

[2] 2306.04678

Heavy QCD axion dark matter from avoided level crossing

The QCD axion offers a natural resolution to the strong CP problem and provides a compelling dark matter candidate. If the QCD axion constitutes all the dark matter, the simplest models pick out a narrow range of masses around $100\,\mu{\rm eV}$. We point out a natural production mechanism for QCD axion dark matter with masses up to the astrophysical bound of $1 \,{\rm eV}$. If the QCD axion mixes with a sterile axion, the relative temperature dependence of their potentials can lead to an avoided level crossing of their mass eigenstates. This leads to a near-total transfer of energy density from the sterile axion to the QCD axion, resulting in a late-time QCD axion abundance sufficient to make up all of present-day dark matter. Our result provides additional theoretical motivation for several direct detection experiments that will probe this part of parameter space in the near future.

[3] 2306.04680

Gravitational waves from phase transitions and cosmic strings in neutrino mass models with multiple Majorons

We explore the origin of Majorana masses within the Majoron model and how this can lead to the generation of a distinguishable primordial stochastic background of gravitational waves. We first show how in the simplest Majoron model only a contribution from cosmic string can be within the reach of planned experiments. We then consider extensions containing multiple complex scalars, demonstrating how in this case a spectrum comprising contributions from both a strong first order phase transition and cosmic strings can naturally emerge. We show that the interplay between multiple scalar fields can amplify the phase transition signal, potentially leading to double peaks over the wideband sloped spectrum from cosmic strings. We also underscore the possibility of observing such a gravitational wave background to provide insights into the reheating temperature of the universe. We conclude highlighting how the model can be naturally combined with scenarios addressing the origin of matter of the universe, where baryogenesis occurs via leptogenesis and a right-handed neutrino plays the role of dark matter.

[4] 2306.04686

Novel approaches to determine $B^\pm$ and $B^0$ meson production fractions

We propose novel methods to determine the $\Upsilon(4S)\to B^+B^-$ and $\Upsilon(4S)\to B^0\bar B^0$ decay rates. The precision to which they and their ratio are known yields at present a limiting uncertainty around $2\%$ in measurements of absolute $B$ decay rates, and thus in a variety of applications, such as precision determinations of elements of the Cabibbo-Kobayashi-Maskawa matrix and flavor symmetry relations. The new methods we propose are based in one case on exploiting the $\Upsilon(5S)$ data sets, in the other case on the different average number of charged tracks in $B^\pm$ and $B^0$ decays. We estimate future sensitivities using these methods and discuss possible measurements of $f_d / f_u$ at the (HL-)LHC.

[5] 2306.04704

Signals of strong parity violation in deep inelastic scattering

We include strong parity-violating contributions to inclusive deep inelastic scattering (DIS) of longitudinally polarized leptons off an unpolarized target. At variance with standard results, we obtain nonvanishing parity-violating structure functions in the case of pure photon exchange. The addition of these strong parity-violating contributions improves the description of existing experimental data on DIS parity violating asymmetries. Their size is small but incompatible with zero at about 1.5-$\sigma$ level.

[6] 2306.04706

Forward $γ$+jet production in proton-proton and proton-lead collisions at LHC within the FoCal calorimeter acceptance

Using the small-$x$ Improved Transverse Momentum Dependent factorization, which can be proved within the Color Glass Condensate theory for transverse momenta of particles greater than the saturation scale, we provide predictions for isolated forward photon and jet production in proton-proton and proton-nucleus collisions within the planned ALICE FoCal detector acceptance. We study azimuthal correlations, $p_T$ spectra, as well as normalized ratios of proton-proton cross sections for different energies. We conclude, that the process provides an excellent probe of the dipole transverse momentum dependent gluon distribution in saturation regime.

[7] 2306.04728

Linear Holographic Hard Wall Model for Glueballs and the Pomeron

In this work we propose a linear holographic hard wall model, modifying the original model by introducing anomalous dimensions for the glueball operators so that we obtain a linear Regge trajectory. We match this Regge trajectory with that of the pomeron with a precision better than $1\%$. The glueball masses obtained in this way are in good agreement with lattice data.

[8] 2306.04869

Form factors of $Ω^-$ in a covariant quark-diquark approach

The electromagnetic and gravitational form factors of $\Omega^-$, a spin-3/2 hyperon composed of three $s$ quarks, are calculated by using a covariant quark-diquark approach. The model parameters are determined by fitting to the form factors of the lattice QCD calculations. Our obtained electromagnetic radii, magnetic moment, and electric-quadrupole moment are in agreement with the experimental measurements and some other model calculations. Furthermore, the mass and spin distributions of $\Omega^-$ from the gravitational form factors are also displayed. It is found that the mass radius is smaller than its electromagnetic ones. Finally, the interpretations of the energy density and momentum current distribution are also discussed.

[9] 2306.04896

The 3+1D initialization and evolution of the Glasma

The IP-Glasma initial condition has been highly successful in the phenomenology of ultra-relativistic heavy ion collisions. The assumption of boost invariance, however, while good for collision energies probed at the LHC, limits the use of IP-Glasma to the transverse dynamics of heavy ion collision to near mid-rapidity. There is a wealth of physics to be explored and understood in the longitudinal dynamics of heavy ion collisions, and a full understanding of heavy ion collisions can only come from 3-dimensional studies. In particular, long range rapidity correlations are seeded in the initial collision and provide additional information on the high energy nuclear wave functions that has thus far been inaccessible to the IP-Glasma model. In this work, we introduce a way to extend the IP-Glasma model to 3+1-dimensions while preserving its key features.

[10] 2306.05207

Prospects for charged Higgs bosons in natural SUSY models at the high-luminosity LHC

We continue our examination of prospects for discovery of heavy Higgs bosons of natural SUSY (natSUSY) models at the high luminosity LHC (HL-LHC), this time focussing on charged Higgs bosons. In natSUSY, higgsinos are expected at the few hundred GeV scale whilst electroweak gauginos inhabit the TeV scale and the heavy Higgs bosons, H, A and H^\pm could range up tens of TeV without jeopardizing naturalness. For TeV-scale heavy SUSY Higgs bosons H, A and H^\pm, as currently required by LHC searches, SUSY decays into gaugino plus higgsino can dominate H^\pm decays provided these decays are kinematically accessible. The visible decay products of higgsinos are soft making them largely invisible, whilst the gauginos decay to W, Z or h plus missing transverse energy (MET). Charged Higgs bosons are dominantly produced at LHC14 via the parton subprocess, gb-> H^\pm t. In this paper, we examine the viability of observing signtures from H^\pm -> \tau\nu, H^\pm -> tb and H^\pm -> W, Z, h + MET events produced in association with a top quark at the HL-LHC over large Standard Model (SM) backgrounds from (mainly) t\bar{t}, t\bar{t}V and t\bar{t}h production (where V=W, Z). We find that the greatest reach is found via the SM H^\pm(-> \tau\nu) +t channel with a subdominant contribution from the H^\pm(-> tb) +t channel. Unlike for neutral Higgs searches, the SUSY decay modes appear to be unimportant for H^\pm searches at the HL-LHC. We delineate regions of the m_A vs. \tan\beta plane, mostly around m_A \sim 1-2 TeV, where signals from charged Higgs bosons would serve to confirm signals of a heavy, neutral Higgs boson at the 5\sigma level or, alternatively, to exclude heavy Higgs bosons at the 95% confidence level at the high luminosity LHC.

[11] 2306.05258

Probing Dual NSI and CP Violation in DUNE and T2HK

The latest results from the long baseline neutrino experiments show a hint of non-zero CP violation in the neutrino sector. In this article, we study the CP violation effects in the upcoming long-baseline neutrino experiments DUNE and T2HK. Non-standard interactions can affect the cleaner determination of CP violation parameter. It has been argued that the NSI can help alleviate the tension between the recent $\delta_{CP}$ measurements of NO$\nu$A and T2K experiments. We consider here the dual NSI due to $\epsilon_{e\mu}$ and $\epsilon_{e\tau}$, arising simultaneously to see the effects in neutrino oscillation probabilities. Moreover, the CP asymmetry parameter $A_{CP}$ exhibits a clear distinction between normal and inverted mass orderings in the DUNE experiment.

[12] 2306.05267

Pseudoscalar meson dominance and nucleon structure

Pseudoscalar meson dominance has implications for nucleon structure which follow from an Extended Partial Conservation of the Axial Current (EPCAC). The minimal resonance saturation of the nucleon pseudoscalar form factor of the lowest pseudoscalar and isovector mesons compatible with pQCD short distance constraints and chiral symmetry. Using PDG tabulated pseudoscalarisovector masses and widths we obtain $g_{\pi NN} = 13.21(^{+0.11}_{-0.06})$, to be compared with the most precise determinations from $np, pp$ scattering, $g_{\pi^+ np} = 13.25(5)$ from the Granada-2013 database. Equivalently a Goldberger-Treiman discrepancy $\Delta_{\rm GT} = 1.8^{+0.9}_{-0.4}\%$ is found. Our results are consistent with almost flat strong pion-nucleon-nucleon vertices.

[13] 2306.05327

Using Earth to Search for Long-Range Spin-Velocity Interactions

Precision measurements of the possible coupling of spin to other scalars, vectors and pseudovectors has proven to be a sensitive way to search for new particle physics beyond the standard model. Indeed, in addition to searching for exotic spin-spin interactions, studies have been undertaken to look for couplings of spin to gravity, the relative velocity between particles, and preferred directions. Several laboratory experiments have established upper bounds on the energy associated with various fermion spin-orientations relative to Earth. Here, we combine these results with a model of Earth in order to investigate the possible long-range spin-velocity interactions associated with the exchange of ultralight ($m_{z'}<1$ neV) or massless scalar or vector bosons. We establish stringent bounds on the strength of these couplings between electrons, neutrons, protons and nucleons.

[14] 2306.05333

FCNC charmed-hadron decays with invisible singlet particles in light of recent data

The flavor-changing neutral current (FCNC) decays of charmed hadrons with missing energy ($\slashed E$) can serve as potentially promising hunting grounds for hints of new physics, as the standard-model backgrounds are very suppressed. A few of such processes have been searched for in recent experiments, particularly $D^0\to\slashed E$ by Belle and $D^0\to\pi^0\slashed E$ and $\Lambda_c^+\to p\slashed E$ by BESIII, resulting in upper bounds on their branching fractions. We consider them to illuminate the possible contributions of the quark transition $c\to u\slashed E$ with a couple of invisible spinless bosons carrying away the missing energy, assuming that they are not charge conjugates of each other and hence can have unequal masses. We find that these data are complementary in that they constrain different sets of the underlying operators and do not cover the same ranges of the bosons' masses, but there are regions not yet accessible. From the allowed parameter space, we show that other $D$-meson decays, such as $D\to\rho\slashed E$, and the charmed-baryon ones $\Xi_c\to(\Sigma,\Lambda)\slashed E$ can have sizable branching fractions and therefore may offer further probes of the new-physics interactions. We point out the importance of $D^0\to\gamma\slashed E$ which are not yet searched for but could access parts of the parameter space beyond the reach of the other modes. In addition, we look at a scenario where the invisibles are instead fermionic, namely sterile neutrinos, and a scalar leptoquark mediates $c\to u\slashed E$. We discuss the implications of the aforesaid bounds for this model. The predictions we make for the various charmed-hadron decays in the different scenarios may be testable in the near future by BESIII and Belle II.

[15] 2306.05389

Towards distinguishing Dirac from Majorana neutrino mass with gravitational waves

We propose to distinguish the nature of neutrino masses, Dirac vs Majorana, from the spectrum of gravitational waves generated. We study two simple models of Majorana and Dirac mass genesis motivated by generating small neutrino masses without assuming tiny Yukawa couplings. For Majorana neutrinos, spontaneous breaking of the gauged $B-L$ symmetry gives a cosmic string induced gravitational wave signal flat over a large range of frequencies, whereas for Dirac neutrinos, spontaneous and soft-breaking of a $Z_2$ symmetry generate a peaked gravitational wave spectrum from annihilation of domain walls. The striking difference between the shape of the spectra in the two cases can help differentiate between Dirac vs Majorana neutrino masses in the two class of models considered, complementing results of neutrinoless double beta decay experiments.

[16] 2306.04442

Dark Matter Constraints from Isomeric $^{\bf 178m}$Hf

We describe a first measurement of the radiation from a $^{\bf 178m}$Hf sample to search for dark matter. The $\gamma$ flux from this sample, possessed by Los Alamos National Laboratory nuclear chemistry, was measured with a Ge detector at a distance of 4 ft due to its high activity. We search for $\gamma$s that cannot arise from the radioactive decay of $^{\bf 178m}$Hf, but might arise from the production of a nuclear state due to the inelastic scattering with dark matter. The limits obtained on this $\gamma$ flux are then translated into constraints on the parameter space of inelastic dark matter. Finally, we describe the potential reach of future studies with $^{\bf 178m}$Hf.

[17] 2306.04687

Causality Bounds in Quadratic Inflation from Purely Virtual Particles

The "$\phi^2$" slow roll inflation combined with General Relativity is largely excluded by Planck data. In this paper, we consider the same potential combined with the $R+C^2$ gravity of purely virtual particles (or fakeons), where the would-be ghost introduced by the Weyl tensor term, $C^2$, is quantized with the fakeon prescription. We compute the tensor power spectrum in the full theory by means of the Cosmic Renormalization Group formalism and critically examine its physical meaning. In particular, we show that it is not possible to retrieve the power spectrum of the fakeon free-theory by considering the decoupling limit of the purely virtual particles. We provide a physical explanation in terms of the causal structure of the theory to infer that a model of quadratic inflation from purely virtual particles is also discarded from a phenomenological point of view.

[18] 2306.04913

Momentum-space second-order pion-nucleus potential including medium effects in the $Δ(1232)$ region

In this work, we develop an updated model for pion-nucleus scattering in the framework of the distorted wave impulse approximation in momentum space. We construct the second-order pion-nucleus potential, which involves analysis of pion-nucleus elastic scattering as a solution of the Lippmann-Schwinger equation. The potential is based on the individual pion-nucleon scattering amplitudes extracted from SAID, and its second-order correction is presented in detail. We estimate optimal energy-independent parameters of the potential by a multi-energy fit of the pion-${}^{12}$C total, reaction, and differential elastic cross sections. We show the predictive power by applying it to pion elastic scattering on ${}^{16}$O, ${}^{28}$Si, and ${}^{40}$Ca.

[19] 2306.05205

Quantum-spacetime effects on nonrelativistic Schrödinger evolution

The last three decades have witnessed the surge of quantum gravity phenomenology in the ultraviolet regime as exemplified by the Planck-scale accuracy of time-delay measurements from highly energetic astrophysical events. Yet, recent advances in precision measurements and control over quantum phenomena may usher in a new era of low-energy quantum gravity phenomenology. In this study, we investigate relativistic modified dispersion relations (MDRs) in curved spacetime and derive the corresponding nonrelativistic Schr\"odinger equation using two complementary approaches. First, we take the nonrelativistic limit, and canonically quantise the result. Second, we apply a WKB-like expansion to an MDR-inspired deformed relativistic wave equation. Within the area of applicability of single-particle quantum mechanics, both approaches imply equivalent results. Surprisingly, we recognise in the generalized uncertainty principle (GUP), the prevailing approach in nonrelativistic quantum gravity phenomenology, the MDR which is least amenable to low-energy experiments. Consequently, importing data from the mentioned time-delay measurements, we constrain the linear GUP up to the Planck scale and improve on current bounds to the quadratic one by 17 orders of magnitude. MDRs with larger implications in the infrared, however, can be tightly constrained in the nonrelativistic regime. We use the ensuing deviation from the equivalence principle to bound some MDRs, for example the one customarily associated with the bicrossproduct basis of the $\kappa$-Poincar\'e algebra, to up to four orders of magnitude below the Planck scale.

[20] 2306.05280

Chiral EFT calculation of neutrino reactions in warm neutron-rich matter

Neutrino scattering and absorption rates of relevance to supernovae and neutron star mergers are obtained from nuclear matter dynamical structure functions that encode many-body effects from nuclear mean fields and correlations. We employ nuclear interactions from chiral effective field theory to calculate the density, spin, isospin, and spin-isospin response functions of warm beta-equilibrium nuclear matter. We include corrections to the single-particle energies in the mean field approximation as well as vertex corrections resummed in the random phase approximation (RPA), including, for the first time, both direct and exchange diagrams. We find that correlations included through the RPA redistribute the strength of the response to higher energy for neutrino absorption and lower energy for antineutrino absorption. This tends to suppress the absorption rate of electron neutrinos across all relevant energy scales. In contrast, the inclusion of RPA correlations enhances the electron antineutrino absorption rate at low energy and supresses the rate at high energy. These effects are especially important at high-density and in the vicinity of the neutrino decoupling region. Implications for heavy element nucleosynthesis, electromagnetic signatures of compact object mergers, supernova dynamics, and neutrino detection from galactic supernovae are discussed briefly.