arXiv subjects

P. S. Bhupal Dev

Publications and source records attributed to P. S. Bhupal Dev.

At least 91 records · Page 5Linked to original sources

arXiv2022

Theories and Experiments for Testable Baryogenesis Mechanisms: A Snowmass White Paper

The baryon asymmetry of the Universe is one of the central motivations to expect physics beyond the Standard Model. In this Snowmass white paper, we review the challenges and opportunities in testing some of the central paradigms that predict physics at scales low enough to expect new experimental data in the next decade. Focusing on theoretical ideas and some of their experimental implications, in particular, we discuss neutron-antineutron transformations, flavor observables, next generation colliders, future neutron facilities, gravitational waves, searches for permanent electric dipole moments, $0νββ$ decay and some future large underground experiments as methods to test post-sphaleron baryogenesis, electroweak baryogenesis, mesogenesis and low scale leptogenesis. Finally, we comment on the cases where high scale physics can be probed through some of these same mechanisms.

hep-ph↗

arXiv2022

Neutrinoless Double Beta Decay via Light Neutralinos in R-Parity Violating Supersymmetry

We perform a study of neutrinoless double beta ($0νββ$) decay mediated by the lightest neutralino of arbitrary mass in the Minimal Supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in $0νββ$ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the Interacting Boson Model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of $0νββ$ decay is then used to place constraints on the supersymmetry parameter space, compatible with constraints from collider experiments. We compare these constraints to bounds from pion decays, CKM unitarity and Big Bang Nucleosynthesis.

hep-ph↗

arXiv2022

Discrete Flavor Symmetries and Lepton Masses and Mixings

We discuss neutrino mass and mixing models based on discrete flavor symmetries. These models can include a variety of new interactions and non-standard particles such as sterile neutrinos, scalar Higgs singlets and multiplets. We point at connections of the models with leptogenesis and dark matter and the ways to detect the corresponding non-standard particles at intensity and energy frontier experiments.

hep-ph↗

arXiv2022

The Forward Physics Facility at the High-Luminosity LHC

High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF's physics potential.

hep-ex↗

arXiv2022

Neutrino Self-Interactions: A White Paper

Neutrinos are the Standard Model (SM) particles which we understand the least, often due to how weakly they interact with the other SM particles. Beyond this, very little is known about interactions among the neutrinos, i.e., their self-interactions. The SM predicts neutrino self-interactions at a level beyond any current experimental capabilities, leaving open the possibility for beyond-the-SM interactions across many energy scales. In this white paper, we review the current knowledge of neutrino self-interactions from a vast array of probes, from cosmology, to astrophysics, to the laboratory. We also discuss theoretical motivations for such self-interactions, including neutrino masses and possible connections to dark matter. Looking forward, we discuss the capabilities of searches in the next generation and beyond, highlighting the possibility of future discovery of this beyond-the-SM physics.

hep-ph↗

arXiv2022

Probing Neutrino Mass Models through Resonances at Neutrino Telescopes

We study the detection prospects of relatively light charged scalars in radiative Majorana neutrino mass models, such as the Zee model and its variants using scalar leptoquarks, at current and future neutrino telescopes. In particular, we show that these scalar mediators can give rise to Glashow-like resonance features in the ultra-high energy neutrino (UHE) event spectrum at the IceCube neutrino observatory and its high-energy upgrade IceCube-Gen2. The same scalars can also give rise to observable non-standard neutrino interactions (NSI), and we show that the UHE neutrinos provide a complementary probe of NSI. We also discuss an interesting possibility of producing such resonances by incoming sterile neutrino components in the case where neutrinos are pseudo-Dirac particles.

hep-ph↗

arXiv2021

Light scalars in neutron star mergers

Due to their unique set of multimessenger signals, neutron star mergers have emerged as a novel environment for studies of new physics beyond the Standard Model (SM). As a case study, we consider the simplest extension of the SM scalar sector involving a light CP-even scalar singlet $S$ mixing with the SM Higgs boson. These $S$ particles can be produced abundantly in neutron star mergers via the nucleon bremsstrahlung process. We show that the $S$ particles may either be trapped in or stream freely out of the merger remnant, depending on the $S$ mass, its mixing with the SM Higgs boson, and the temperature and baryon density in the merger. In the free-streaming region, the scalar $S$ will provide an extra channel to cool down the merger remnant, with cooling timescales as small as ${\cal O}$(ms). On the other hand, in the trapped region, the Bose gas of $S$ particles could contribute a larger thermal conductivity than the trapped neutrinos in some parts of the parameter space, thus leading to faster thermal equilibration than expected. Therefore, future observations of the early postmerger phase of a neutron star merger could effectively probe a unique range of the $S$ parameter space, largely complementary to the existing and future laboratory and supernova limits. In view of these results, we hope the merger simulation community will be motivated to implement the effects of light CP-even scalars into their simulations in both the free-streaming and trapped regimes.

hep-ph↗

arXiv2021

Meeting the Challenges for Relic Neutrino Detection

Inspired by Gounaris-Sakurai and Lee-Zumino, we postulate that the weak vector and axial vector currents are dominated by $J^{PC} = 1^{--}$ and $1^{++}$ resonances respectively in the appropriate channels of $ν+ \bar ν$ annihilation into quark-antiquark pairs when an ultrahigh-energy incoming $ν\ (\bar ν)$ strikes a relic $\bar ν\ (ν)$. Despite this and some other ideas, it appears the detection of relic neutrinos with just the Standard Model interactions seems extremely difficult at existing or future neutrino telescopes. Thus any positive signal would be due to some non-standard interactions of neutrinos.

hep-ph↗

arXiv2021

Leptophilic Dark Matter at Linear Colliders

We discuss model-independent collider constraints on the effective couplings of leptophilic dark matter (LDM), considering its production at a future electron-positron linear collider, with both polarized and unpolarized beam options, in the mono-photon and mono-$Z$ channels. We show that the future collider constraints are largely complementary to the direct and indirect detection limits on LDM, and can potentially provide the best-ever LDM sensitivity in the low-mass regime (below $\sim$ 10 GeV).

hep-ph↗

arXiv2021

PASSAT at Future Neutrino Experiments: Hybrid Beam-Dump-Helioscope Facilities to Probe Light Axion-Like Particles

There are broadly three channels to probe axion-like particles (ALPs) produced in the laboratory: through their subsequent decay to Standard Model (SM) particles, their scattering with SM particles, or their subsequent conversion to photons. Decay and scattering are the most commonly explored channels in beam-dump type experiments, while conversion has typically been utilized by light-shining-through-wall (LSW) experiments. A new class of experiments, dubbed PASSAT (Particle Accelerator helioScopes for Slim Axion-like-particle deTection), has been proposed to make use of the ALP-to-photon conversion in a novel way: ALPs, after being produced in a beam-dump setup, turn into photons in a magnetic field placed near the source. It has been shown that such hybrid beam-dump-helioscope experiments can probe regions of parameter space that have not been investigated by other laboratory-based experiments, hence providing complementary information; in particular, they probe a fundamentally different region than decay or LSW experiments. We propose the implementation of PASSAT in future neutrino experiments, taking a DUNE-like experiment as an example. We demonstrate that the magnetic field in the planned DUNE multi-purpose detector is already capable of probing the ALP-photon coupling down to $g_{aγγ} \sim {\rm few}\times 10^{-5}$ GeV$^{-1}$ for ALP masses $m_a \lesssim 10$ eV. The implementation of a CAST or BabyIAXO-like magnet would improve the sensitivity down to $g_{aγγ} \sim 10^{-6}$ GeV$^{-1}$.

hep-ph↗

arXiv2021

New Interference Effects from Light Gauge Bosons in Neutrino-Electron Scattering

We point out that light gauge boson mediators could induce new interference effects in neutrino-electron scattering that can be used to enhance the sensitivity of neutrino-flavor-selective high-intensity neutrino experiments, such as DUNE. We particularly emphasize a destructive interference effect, leading to a deficit between the Standard Model expectation and the experimental measurement of the differential cross-sections, which is prominent only in either the neutrino or the antineutrino mode, depending on the mediator couplings. Therefore, the individual neutrino (or antineutrino) mode could allow for sensitivity reaches superior to the combined analysis, and moreover, could distinguish between different types of gauge boson mediators.

hep-ph↗

arXiv2021

Impact of Improved Energy Resolution on DUNE sensitivity to Neutrino Non-Standard Interactions

The full physics potential of the next-generation Deep Underground Neutrino Experiment (DUNE) is still being explored. In particular, there have been some recent studies on the possibility of improving DUNE's neutrino energy reconstruction. The main motivation is that a better determination of the neutrino energy in an event-by-event basis will translate into an improved measurement of the Dirac $CP$ phase and other neutrino oscillation parameters. To further motivate studies and improvements on the neutrino energy reconstruction, we evaluate the impact of energy resolution at DUNE on an illustrative new physics scenario, viz. non-standard interactions (NSI) of neutrinos with matter. We show that a better energy resolution in comparison to the ones given in the DUNE conceptual and technical design reports may significantly enhance the experimental sensitivity to NSI, particularly when degeneracies are present. While a better reconstruction of the first oscillation peak helps disentangling standard $CP$ effects from those coming from NSIs, we find that the second oscillation peak also plays a nontrivial role in improving DUNE's sensitivity.

hep-ph↗

arXiv2021

Light, Long-Lived $B-L$ Gauge and Higgs Bosons at the DUNE Near Detector

The low-energy $U(1)_{B-L}$ gauge symmetry is well-motivated as part of beyond Standard Model physics related to neutrino mass generation. We show that a light $B-L$ gauge boson $Z{'}$ and the associated $U(1)_{B-L}$-breaking scalar $φ$ can both be effectively searched for at high-intensity facilities such as the near detector complex of the Deep Underground Neutrino Experiment (DUNE). Without the scalar $φ$, the $Z{'}$ can be probed at DUNE up to mass of 1 GeV, with the corresponding gauge coupling $g_{BL}$ as low as $10^{-9}$. In the presence of the scalar $φ$ with gauge coupling to $Z{'}$, the DUNE capability of discovering the gauge boson $Z{'}$ can be significantly improved, even by one order of magnitude in $g_{BL}$, due to additional production from the decay $φ\to Z{'}Z{'}$. The DUNE sensitivity is largely complementary to other long-lived $Z{'}$ searches at beam-dump facilities such as FASER and SHiP, as well as astrophysical and cosmological probes. On the other hand, the prospects of detecting $φ$ itself at DUNE are to some extent weakened in presence of $Z{'}$, compared to the case without the gauge interaction.

hep-ph↗

arXiv2021

Searching for $Z'$ bosons at the P2 experiment

The P2 experiment aims at high-precision measurements of the parity-violating asymmetry in elastic electron-proton and electron-$^{12}$C scatterings with longitudinally polarized electrons. We discuss here the sensitivity of P2 to new physics mediated by an additional neutral gauge boson $Z'$ of a new $U(1)'$ gauge symmetry. If the charge assignment of the $U(1)'$ is chiral, i.e., left- and right-handed fermions have different charges under $U(1)'$, additional parity-violation is induced directly. On the other hand, if the $U(1)'$ has a non-chiral charge assignment, additional parity-violation can be induced via mass or kinetic $Z$-$Z'$ mixing. By comparing the P2 sensitivity to existing constraints, we show that in both cases P2 has discovery potential over a wide range of $Z'$ mass. In particular, for chiral models, the P2 experiment can probe gauge couplings at the order of $10^{-5}$ when the $Z'$ boson is light, and heavy $Z'$ bosons up to 79 (90) TeV in the proton ($^{12}$C) mode. For non-chiral models with mass mixing, the P2 experiment is sensitive to mass mixing angles smaller than roughly $10^{-4}$, depending on model details and gauge coupling magnitude.

hep-ph↗

arXiv2021

Stellar limits on light CP-even scalar

We revisit the astrophysical constraints on a generic light CP-even scalar particle $S$, mixing with the Standard Model (SM) Higgs boson, from observed luminosities of the Sun, red giants, white dwarfs and horizontal-branch stars. The production of $S$ in the stellar core is dominated by the electron-nuclei bremsstrahlung process $e + N \to e + N + S$. With the $S$ decay and reabsorption processes taken into consideration, we find that the stellar luminosity limits exclude a broad range of parameter space in the $S$ mass-mixing plane, with the scalar mass up to 350 keV and the mixing angle ranging from $7.0\times10^{-18}$ to $3.4\times10^{-3}$. We also apply the stellar limits to a real-singlet scalar extension of the SM, where we can relate the mixing angle to the parameters in the scalar potential. In both the generic scalar case and the real-singlet extension, we show that the stellar limits preclude the scalar interpretation of the recently observed XENON1T excess in terms of the $S$ particles emitted from the Sun.

hep-ph↗

arXiv2021

Unified Framework for $B$-Anomalies, Muon $g-2$, and Neutrino Masses

We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(\star)}}$ and $R_{K^{(\star)}}$, as well as in muon $g-2$ measurement, $Δa_μ$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(\star)}}$, $R_{K^{(\star)}}$ and $Δa_μ$ within $1\, σ$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the $S_3$ LQ, which enhances its reach to 1.1 (6.2) TeV at $\sqrt s=14$ TeV high-luminosity LHC ($\sqrt s=100$ TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton ($pp \rightarrow \ell^+ \ell^-$) processes mediated by $t$-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range $(0.15 - 0.36)$. These limits preclude any explanation of $R_{D^{(\star)}}$ through LQ-mediated $B$-meson decays involving $ν_e$ or $ν_μ$ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to $Δa_μ$ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2-6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.

hep-ph↗

arXiv2021

Fast radio bursts from axion stars moving through pulsar magnetospheres

We study the radio signals generated when an axion star enters the magnetosphere of a neutron star. As the axion star moves through the resonant region where the plasma-induced photon mass becomes equal to the axion mass, the axions can efficiently convert into photons, giving rise to an intense, transient radio signal. We show that a dense axion star with a mass $\sim 10^{-13}M_{\odot}$ composed of $\sim 10\: μ$eV axions can account for most of the mysterious fast radio bursts.

astro-ph.HE↗

arXiv2020

Unified explanation of flavor anomalies, radiative neutrino mass and ANITA anomalous events in a vector leptoquark model

Driven by the recent experimental hints of lepton-flavor-universality violation in the bottom-quark sector, we consider a simple extension of the Standard Model (SM) with an additional vector leptoquark $V_{\rm LQ}({\bf 3},{\bf 1},2/3)$ and a scalar diquark $S_{\rm DQ}({\bf 6},{\bf 1},4/3)$ under the SM gauge group $SU(3)_c\times SU(2)_L\times U(1)_Y$, in order to simultaneously explain the $b \to s \ell^+ \ell^-$ (with $\ell=e,μ$) and $b \to c l^- \bar ν_l$ (with $l=e,μ,τ$) flavor anomalies, as well as to generate small neutrino masses through a two-loop radiative mechanism. We perform a global fit to all the relevant and up-to-date $b \to s \ell^+ \ell^-$ and $b \to c l^- \bar ν_l$ data under the assumption that the leptoquark couples predominantly to second and third-generation SM fermions. We then look over the implications of the allowed parameter space on lepton-flavor-violating $B$ and $τ$ decay modes, such as $B_s \to l^+_i l^-_j, \ B \to K^{(*)} l^+_i l^-_j, \ B_s \to ϕl^+_i l^-_j$, $Υ(nS) \to μτ$ and $τ\to μγ$, $τ\to μϕ(η^{(\prime)})$, respectively. Minimally extending this model by adding a fermion singlet $χ({\bf 1},{\bf 1},0)$ also explains the ANITA anomalous upgoing events. Furthermore, we provide complementary constraints on leptoquark and diquark couplings from high-energy collider and other low-energy experiments to test this model.

hep-ph↗