HEP Phenomenology·hep-ph
23 papers—14 primary·9 cross-listed·reconstructed*
The current article reviews results on vacuum Cherenkov radiation obtained for modified fermions. Two classes of processes can occur that have completely distinct characteristics. The first one does not include a spin flip of the radiating fermion, whereas the second one does. A résumé will be given of the decay rates for these processes and their properties.
Imtiyaz Ahmad Bhat🇮🇳 · Rathin Adhikari🇮🇳
In a model with an extra gauge to SM gauge group, we have shown the allowed region of masses of extra gauge boson and the dark matter which is the lightest one among other right-handed Majorana fermions present in the model. To obtain this region, we have used bounds coming from constraints on active-sterile neutrino masses and mixing from various oscillation experiments, constraint on dark matter relic density obtained by PLANCK together with the constraint on the extra gauge boson mass and its gauge coupling recently obtained by ATLAS Collaboration at LHC. From the allowed regions, it is possible to get some lower bounds on the masses of the extra gauge boson and the dark matter and considering those values it is possible to infer what could be the spontaneous symmetry breaking scale of an extra gauge symmetry.
Nayara Fonseca🇩🇪 · Benedict von Harling🇩🇪 · Leonardo de Lima🇧🇷 · Camila S. Machado🇩🇪
We present a novel framework for obtaining large hierarchies in axion decay constants as well as trans-Planckian field excursions, with no need for tuning or a large number of fields. We consider a model with two or more CFTs with a common cutoff, that are linked by a gauged diagonal symmetry. This construction is dual to the geometry of a warped space with two or more throats glued at a common brane, allowing for calculability. Many applications of our setup are possible,such as ultra-light axions, natural inflation, and relaxion models.
Tatsuo Kobayashi🇯🇵 · Yusuke Shimizu🇯🇵 · Kenta Takagi🇯🇵 · Morimitsu Tanimoto🇯🇵 · Takuya H. Tatsuishi🇯🇵
We present a flavor model with the modular invariance in the framework of SU(5) GUT. The modular forms of weights and give the quark and lepton mass matrices with a common complex parameter, the modulus . The GUT relation of down-type quarks and charged leptons is imposed by the VEV of adjoint 24-dimensional Higgs multiplet in addition to the VEVs of and Higgs multiples of SU(5). The observed CKM and PMNS mixing parameters as well as the mass eigenvalues are reproduced properly. We discuss the leptonic CP phase and the effective mass of the neutrinoless double beta decay with the sum of neutrino masses.
G. Arcadi🇩🇪 · C. Döring🇩🇪 · C. Hasterok🇩🇪 · S. Vogl🇩🇪
Direct detection experiments aim at the detection of dark matter in the form of weakly interacting massive particles (WIMPs) by searching for signals from elastic dark matter nucleus scattering. Additionally, inelastic scattering in which the nucleus is excited is expected from nuclear physics and provides an additional detectable signal. In the context of a low-energy effective field theory we investigate the experimental reach to these inelastic transitions for xenon-based detectors employing a dual-phase time projection chamber. We find that once a dark matter signal is established, inelastic transitions enhance the discovery reach and we show that they allow a better determination of the underlying particle physics.
Simone Marzani🇮🇹 · Daniel Reichelt🇩🇪 · Steffen Schumann🇩🇪 · Gregory Soyez🇫🇷 · Vincent Theeuwes🇩🇪
Soft drop has been shown to reduce hadronisation effects at colliders for the thrust event shape. In this context, we perform fits of the strong coupling constant for the soft-drop thrust distribution at NLO+NLL accuracy to pseudo data generated by the \textsf{Sherpa}~event generator. In particular, we focus on the impact of hadronisation corrections, which we estimate both with an analytical model and a Monte-Carlo based one, on the fitted value of . We find that grooming can reduce the size of the shift in the fitted value of due to hadronisation. In addition, we also explore the possibility of extending the fitting range down to significantly lower values of (one minus) thrust. Here, soft drop is shown to play a crucial role, allowing us to maintain good fit qualities and stable values of the fitted strong coupling. The results of these studies show that soft-drop thrust is a promising candidate for fitting at colliders with reduced impact of hadronisation effects.
Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷
When a small vacuum expectation value of Higgs triplet () in the type-II seesaw model is required to explain neutrino oscillation data, a fine-tuning issue occurs on the mass-dimension lepton-number-violation (LNV) scalar coupling. Using the scotogenic approach, we investigate how a small LNV term is arisen through a radiative correction when an -odd vector-like lepton () and an -odd right-handed Majorana lepton () are introduced to the type-II seesaw model. Due to the dark matter (DM) direct detection constraints, the available DM candidate is the right-handed Majorana particle, whose mass depends on and is close to the parameter. Combing the constraints from the DM measurements, the decay, and the oblique -parameter, it is found that the preferred range of is approximately in the region of GeV; the mass difference between the doubly and the singly charged Higgs is less than 50 GeV, and the influence on the is not significant. Using the constrained parameters, we analyze the decays of each Higgs triplet scalar in detail, including the possible three-body decays when the kinematic condition is allowed. It is found that with the exception of doubly charged Higgs, scalar mixing effects play an important role in the Higgs triplet two-body decays when the scalar masses are near-degenerate. In the non-degenerate mass region, the branching ratios of the Higgs triplet decays are dominated by the three-body decays.
We study the ratio of the cross sections for and production at the LHC. The presence of correlations between theoretical uncertainties of the two processes makes possible a precise determination of this observable. This can help to evidentiate effects of new physics that might reveal themselves only when sufficiently precise theoretical predictions are available. Our analysis is based on fully realistic simulations of and production in the dilepton decay channel, including complete off-shell and non-resonant effects at NLO QCD accuracy. We discuss Standard Model predictions for the LHC Run II at both inclusive and differential level, also quantifying the impact of the theoretical uncertainties related to variation of scales and parton distribution functions.
Duong Van Loi🇻🇳 · Phung Van Dong🇻🇳 · Le Xuan Thuy🇻🇳
It is well established that the gauge symmetry for can address the question of fermion generation number due to the anomaly cancellation, but it neither commutes nor closes algebraically with electric and baryon-minus-lepton charges. Hence, two factors that determine such charges are required, yielding a complete gauge symmetry, , apart from the color group. The resulting theory manifestly provides neutrino mass, dark matter, inflation, and baryon asymmetry of the universe. Furthermore, this gauge structure may present kinetic mixing effects associated to the gauge fields, which affect the electroweak precision test such as the parameter and couplings as well as the new physics processes. We will construct the model, examine the interplay between the kinetic mixing and those due to the symmetry breaking, and obtain the physical results in detail.
Sanjoy Biswas🇮🇳 · Anirban Chatterjee🇮🇳 · Emidio Gabrielli🇮🇹 · Barbara Mele🇮🇹
We study portal interactions connecting visible and dark sectors, and involving local interactions of a photon, a dark photon and a axion-like particle (ALP) at future colliders. These interactions, mediated by higher-dimensional effective operators, may arise at one-loop by kinetic mixing between dark and ordinary photons, or, for massless dark photons, by direct short-distance contributions. We explore these portal interactions for a heavy ALP with masses between about 10 GeV and 230 GeV by investigating the sensitivity of the production to the effective couplings, where the dark photon gives rise to missing momentum in the final state. We will show how an appropriate choice of missing-energy and missing-mass cuts can optimize the signal to standard-model background ratio. Exclusion regions for the effective photon-dark-photon-ALP couplings versus the ALP mass are worked out for a few representative values of the collision energy and integrated luminosity, as presently envisaged by future projects.
I discuss recent progress on fits to dimension-six operators in the Standard Model Effective Theory (SMEFT). I focus on the top quark sector of the SMEFT, as well as the theoretical advances made in computing SMEFT effects through to next-to-leading order in QCD and the use of these calculations in global fits. I also discuss fits performed to the Higgs and electroweak sectors of the SMEFT and the possibility for performing global fits to multiple sectors simultaneously.
The NNPDF Collaboration: Rabah Abdul Khalek🇳🇱 · Richard D. Ball🇬🇧 · Stefano Carrazza🇮🇹 · Stefano Forte🇮🇹 · Tommaso Giani🇬🇧 · Zahari Kassabov🇬🇧 · Rosalyn L. Pearson🇬🇧 · Emanuele R. Nocera🇳🇱 · Juan Rojo🇳🇱 · Luca Rottoli🇮🇹 · Maria Ubiali🇬🇧 · Cameron Voisey🇬🇧 · Michael Wilson🇬🇧
We formulate a general approach to the inclusion of theoretical uncertainties, specifically those related to the missing higher order uncertainty (MHOU), in the determination of parton distribution functions (PDFs). We demonstrate how, under quite generic assumptions, theory uncertainties can be included as an extra contribution to the covariance matrix when determining PDFs from data. We then review, clarify, and systematize the use of renormalization and factorization scale variations as a means to estimate MHOUs consistently in deep inelastic and hadronic processes. We define a set of prescriptions for constructing a theory covariance matrix using scale variations, which can be used in global fits of data from a wide range of different processes, based on choosing a set of independent scale variations suitably correlated within and across processes. We set up an algebraic framework for the choice and validation of an optimal prescription by comparing the estimate of MHOU encoded in the next-to-leading order (NLO) theory covariance matrix to the observed shifts between NLO and NNLO predictions. We perform a NLO PDF determination which includes the MHOU, assess the impact of the inclusion of MHOUs on the PDF central values and uncertainties, and validate the results by comparison to the known shift between NLO and NNLO PDFs. We finally study the impact of the inclusion of MHOUs in a global PDF determination on LHC cross-sections, and provide guidelines for their use in precision phenomenology. In addition, we also compare the results based on the theory covariance matrix formalism to those obtained by performing PDF determinations based on different scale choices.
Melissa van Beekveld🇳🇱 · Sascha Caron🇳🇱 · Roberto Ruiz de Austri🇪🇸
In this paper, we minimize and compare two different fine-tuning measures in four high-scale supersymmetric models that are embedded in the MSSM. In addition, we determine the impact of current and future dark matter direct detection and collider experiments on the fine-tuning. We then compare the low-scale electroweak measure with the high-scale Barbieri-Giudice measure, which generally do not agree. However, we find that they do reduce to the same value when the higgsino parameter drives the degree of fine-tuning. Depending on the high-scale model and fine-tuning definition, we find a minimal fine-tuning of (corresponding to ) for the low-scale measure, and (corresponding to ) for the high-scale measure. In addition, minimally fine-tuned spectra give rise to a dark matter relic density that is between , when determines the minimum of the fine-tuning. We stress that it is too early to conclude on the fate of supersymmetry, based only on the fine-tuning paradigm.
Hidekazu Tanaka🇯🇵 · Shuji Sasagawa🇯🇵
Chiral symmetry restoration of quarks is investigated at finite density in quantum chromodynamics. The effective quark mass is calculated with the Schwinger-Dyson equation in the real-time formalism without the instantaneous exchange approximation. We present some properties of the quark mass functions and the quark propagator at zero temperature.
John Ellis🇬🇧 · Dimitri V. Nanopoulos🇺🇸 · Keith A. Olive🇺🇸 · Sarunas Verner🇺🇸
We have presented previously a general treatment of Starobinsky-like inflation in no-scale supergravity where the tensor-to-scalar ratio , and is the tilt of the scalar perturbations. In particular, we have shown how this scenario can be unified with modulus fixing, supersymmetry breaking and a small cosmological constant. In this paper we extend these constructions to inflationary models based on generalized no-scale structures. In particular, we consider alternative values of the curvature parameter, , as may occur if not all the complex Kähler moduli contribute to driving inflation, as well as , as may occur if complex structure moduli also contribute to driving inflation. In all cases, we combine these -Starobinsky inflation models with supersymmetry breaking and a present-day cosmological constant, allowing for additional contributions to the vacuum energy from stages of gauge symmetry breaking.
Péter Mészáros🇺🇸 · Derek B. Fox🇺🇸 · Chad Hanna🇺🇸 · Kohta Murase🇺🇸
Multi-messenger astrophysics, a long-anticipated extension to traditional and multiwavelength astronomy, has recently emerged as a distinct discipline providing unique and valuable insights into the properties and processes of the physical universe. These insights arise from the inherently complementary information carried by photons, gravitational waves, neutrinos, and cosmic rays about individual cosmic sources and source populations. Realizing the observation of astrophysical sources via non-photonic messengers has presented enormous challenges, as evidenced by the fiscal and physical scales of the multi-messenger observatories. However, the scientific payoff has already been substantial, with even greater rewards promised in the years ahead. In this review we survey the current status of multi-messenger astrophysics, highlighting some exciting recent results, and addressing the major follow-on questions they have raised. Key recent achievements include the measurement of the spectrum of ultra-high energy cosmic rays out to the highest observable energies; discovery of the diffuse high energy neutrino background; the first direct detections of gravitational waves and the use of gravitational waves to characterize merging black holes and neutron stars in strong-field gravity; and the identification of the first joint electromagnetic + gravitational wave and electromagnetic + high-energy neutrino multi-messenger sources. We then review the rationales for the next generation of multi-messenger observatories, and outline a vision of the most likely future directions for this exciting and rapidly advancing field.
Daniel Baumann🇳🇱 · Daniel Green🇺🇸 · Thomas Hartman🇺🇸
Sum rules connecting low-energy observables to high-energy physics are an interesting way to probe the mechanism of inflation and its ultraviolet origin. Unfortunately, such sum rules have proven difficult to study in a cosmological setting. Motivated by this problem, we investigate a precise analogue of inflation in anti-de Sitter spacetime, where it becomes dual to a slow renormalization group flow in the boundary quantum field theory. This dual description provides a firm footing for exploring the constraints of unitarity, analyticity, and causality on the bulk effective field theory. We derive a sum rule that constrains the bulk coupling constants in this theory. In the bulk, the sum rule is related to the speed of radial propagation, while on the boundary, it governs the spreading of nonlocal operators. When the spreading speed approaches the speed of light, the sum rule is saturated, suggesting that the theory becomes free in this limit. We also discuss whether similar results apply to inflation, where an analogous sum rule exists for the propagation speed of inflationary fluctuations.
We carry out a systematic study of Yang-Mills theory endowed with fermions in the adjoint and -index antisymmetric mixed-representation. The fermion bilinear in the -index antisymmetric representation vanishes identically, which leads to interesting new phenomena. We first study the theory on a small circle, i.e., on , employing symmetry-twisted boundary conditions and semi-classical techniques. We find that the ground state is -fold degenerate, which can be explained as a consequence of a -form/-form mixed 't Hooft anomaly. In addition, the theory may admit massless bosonic and fermionic degrees of freedom, depending on the number of flavors, and confines the electric probes in the infrared. Empowered by 't Hooft anomaly matching conditions along with the -loop -function, we further examine the possible infrared symmetry realizations on for various number of adjoint and -index antisymmetric fermions. The infrared theory is either a conformal field theory, which is expected for a large number of flavors, or it is confining with or without chiral symmetry breaking. In a few cases, we are able to give enough evidence for adiabatic continuity between the small- and large-circle limits.
Satoshi X. Nakamura (University of Science and Technology of China)🇨🇳
I overview our recent activity with the Argonne-Osaka dynamical coupled-channels (DCC) approach that provides a unified description of various electroweak meson productions on single nucleon and nucleus. First I discuss the DCC model of a single nucleon. The DCC model has been developed through a comprehensive analysis of reaction data. The model has been further extended to finite region by analyzing pion electroproduction data, and to neutrino-induced reactions using the PCAC relation. Next I discuss applications of the DCC model to electroweak meson productions on the deuteron. We consider impulse mechanism supplemented by final state interactions (FSI) due to and meson-nucleon rescatterings. Using this model, I discuss FSI corrections needed to extract -neutron reaction observables from , and a novel method to extract scattering length from . I also discuss FSI corrections on the existing neutrino-nucleon pion production data that had been extracted from neutrino-deuteron data.
Bo-Qiang Lu🇨🇳 · Yue-Liang Wu🇨🇳
We propose that the kinematical observations of dwarf galaxies can be used to constrain the primordial black hole's (PBH) abundance in dark matter since the presence of primordial black holes in star clusters will lead to the radial velocity dispersion of the system. For instance, using the velocity dispersion observations from Leo I we show that the primordial black hole fraction is ruled out at a 99.99\% confidence level. This method yields the most stringent limits on the PBH abundance at the mass scales and tightly constrains the primordial origin of gravitational wave events observed by the LIGO experiments.
The search for lepton flavour violation in charged lepton decays is highly sensitive to physics beyond the Standard Model. Among the possible processes, -decays are considered to have the largest discovery potential in most of the standard model extensions. Many searches has been performed in the past, however no evidence has been found so far. Four dedicated experiments are in advanced state of preparation to improve the current associated sensibilities by 1-4 order of magnitudes for the charged lepton flavour violating processes , conversion and . In this paper I present physics motivations, experimental challenges and construction status of the experiments, which are the studying above mentioned processes.
L.A. Harewood🇺🇸 · R. Gran🇺🇸
Rescattering following a neutrino-nucleus reaction changes the number, energy, and direction of detectable hadrons. In turn, this affects the selection and kinematic distributions of subsamples of neutrino events used for interaction or oscillation analysis. This technical note focuses on three forms of two-body rescattering. Elastic hadron+nucleus scattering primarily changes the direction of the hadron with very little energy transfer. Secondly, a hadron+nucleon quasi-elastic process leads to the knockout of a single struck nucleon, possibly with charge exchange between the two hadrons. Also, a pion can be absorbed leading to the ejection of two nucleons. There was an error in the code of the {\small GENIE} neutrino event generator that affects these processes. We present examples of the change with the fixed version of the scattering process, but also compare these specifically to turning off elastic scattering completely, which is similar to other neutrino event generator configurations or a potential Equick-fix to already generated samples. Three examples are taken from current topics of interest: transverse kinematics observables in quasielastic neutrino reactions, the pion angle with respect to the incoming and outgoing lepton for reactions with a charged pion in the final state, and the angle between two protons in reactions with no pions present. Elastic hadron+nucleus scattering in its unfixed form makes a large distortion in distributions of transverse kinematic imbalances scattering, but only mild distortion in other observables. The distortion of the other two processes is also mild for all distributions considered. The correct form of hadron+nucleus scattering process could play a role in describing the width and center of the sharp peak in the inferred Fermi-motion of the struck nucleon or be benchmarked using (e,e'p) data.
Jean Alexandre🇬🇧 · Katy Clough🇬🇧
Setting aside anthropic arguments, there is no reason why the universe should initially favour a net expanding phase rather than one experiencing a net contraction. However, a collapsing universe containing "normal" matter will end at a singularity in a finite time. We point out that there is a mechanism, derived from non-perturbative effects in Quantum Field Theory in a finite volume, which may provide a bias towards expansion when the spacetime volume shrinks, by dynamically violating the null energy condition, without the need for modified gravity or exotic matter. We describe a scalar field component subjected to this non-perturbative effect in a cosmological background and consider its impact on a contracting phase. We discuss how this could dynamically generate the necessary initial conditions for inflation to get started, or form part of the mechanism for a non-singular cosmological bounce.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.