HEP Phenomenology·hep-ph
37 papers—23 primary·14 cross-listed·reconstructed*
Bipin Singh Koranga🇮🇳 · Vivek Kumar Nautiyal🇮🇳
We consider the effects of Planck scale on four flavour neutrino mixings. The gravational interaction at , we find that for degenerate neurino mass order, the Planck scale effects changes the mixing angle , values and , , , are unchanged above the GUT scale. In this paper, we study neutrino mixing in four flavor above the GUT scale.
Arghyajit Datta🇮🇳 · Biswajit Karmakar🇵🇱 · Arunansu Sil🇮🇳
We propose a minimal flavor symmetric model, assisted by symmetry, which can naturally takes care of the appropriate lepton mixing and neutrino masses via Type-I seesaw. It turns out that the framework, originated due to a specific flavor structure, favors the normal hierarchy of light neutrinos and simultaneously narrows down the range of Dirac CP violating phase. It predicts an interesting correlation between the atmospheric mixing angle and the Dirac CP phase too. While the flavor structure indicates an exact degeneracy of the right handed neutrino masses, renormalization group running of the same from a high scale is shown to make it quasi-degenerate and a successful flavor leptogenesis takes place within the allowed parameter space obtained from neutrino phenomenology.
Wafaa Saleh🇪🇬 · Asmaa G. Shalaby🇪🇬
The transverse momentum distribution of charged particles formed in AuAu collisions at Beam Energy Scan (BES) ( 7.7, 11.5, 19.6, 27, 39 ) is investigated. In addition, spectra of particle at =62.4 was examined. Tsallis distribution is used to extract the temperature, volume and the entropic index from the experimental results at mid-rapidity and zero chemical potential. We measure some particle ratios like and which are puzzling horn in the experiment and in the thermal model. We conclude that the horn vanished when we used Tsallis distribution, but this does not confirm a solution to the puzzle, which is primarily visible in the experimental results.
Koji Nagano🇯🇵 · Hiromasa Nakatsuka🇯🇵 · Soichiro Morisaki🇺🇸 · Tomohiro Fujita🇯🇵 · Yuta Michimura🇯🇵 · Ippei Obata🇩🇪
Axion is a promising candidate for ultralight dark matter which may cause a polarization rotation of laser light. Recently, a new idea of probing the axion dark matter by optical linear cavities used in the arms of gravitational wave detectors has been proposed [Phys. Rev. Lett. 123, 111301 (2019)]. In this article, a realistic scheme of the axion dark matter search with the arm cavity transmission ports is revisited. Since photons detected by the transmission ports travel in the cavity for odd-number of times, the effect of axion dark matter on their phases is not cancelled out and the sensitivity at low-mass range is significantly improved compared to the search using reflection ports. We also take into account the stochastic nature of the axion field and the availability of the two detection ports in the gravitational wave detectors. The sensitivity to the axion-photon coupling, , of the ground-based gravitational wave detector, such as Advanced LIGO, with 1-year observation is estimated to be GeV below the axion mass of eV, which improves upon the limit achieved by the CERN Axion Solar Telescope.
Fraga Jorge🇨🇴 · Rodriguez Ronald🇨🇴 · Solano Jesus🇨🇴 · Molano Juan🇨🇴 · Avila Carlos🇨🇴
A study of four different machine learning (ML) algorithms is performed to determine the most suitable ML technique to disentangle a hypothetical supersymmetry signal from its corresponding Standard Model (SM) backgrounds and to establish their impact on signal significance. The study focuses on the production of SUSY top squark pairs (stops), in the mass range of GeV, from proton-proton collisions with a center of mass energy of 13 TeV and an integrated luminosity of 150 fb, emulating the data-taking conditions of the run II LHC accelerator. In particular, the semileptonic channel is analyzed, corresponding to final states with a single isolated lepton (electron or muon), missing transverse energy, and four jets, with at least one tagged as -jet. The challenging compressed spectra region is targeted, where the stop decays mainly into a boson, a -jet, and a neutralino (), with a mass gap between the stop and the neutralino of about 150 GeV. The ML algorithms are chosen to cover different mathematical implementations and features in machine learning. We compare the performance of a logistic regression (LR), a Random Forest (RF), an XGBoost (XG), and a Neural Network (NN) algorithm. Our results indicate that all four algorithms provide an improvement in signal significance calculation when compared to the ones obtained with a standard analysis method based on sequential requirements of different kinematic variables. The highest gain in significance is obtained with the NN and XG classifiers with an average improvement over 20\%, both having compatible statistical performance for the stop mass range considered, followed by RF(15\%). The LR has the poorest performance of all ML algorithms studied, but still presents an average improvement of about 4\%.
This is a concise introduction to the topic of nonextensive Tsallis statistics meant especially for those interested in its relation to high energy proton-proton, proton-nucleus, and nucleus-nucleus collisions. The three types of Tsallis statistics are reviewed. Only one of them is consistent with the fundamental hypothesis of equilibrium statistical mechanics. The single particle distributions associated with it, namely Boltzmann, Fermi-Dirac, and Bose-Einstein, are derived. These are not equilibrium solutions to the conventional Boltzmann transport equation which must be modified in a rather nonintuitive manner for them to be so. Nevertheless the Boltzmann limit of the Tsallis distribution is extremely efficient in representing a wide variety of single particle distributions in high energy proton-proton, proton-nucleus, and nucleus-nucleus collisions with only three parameters, one of them being the so-called nonextensitivity parameter . This distribution interpolates between an exponential at low transverse energy, reflecting thermal equilibrium, to a power law at high transverse energy, reflecting the asymptotic freedom of QCD. It should not be viewed as a fundamental new parameter representing nonextensive behavior in these collisions.
Eugene Levin (Tel Aviv U./UTFSM)🇮🇱
In this paper we derived in QCD the BFKL linear, inhomogeneous equation for the factorial moments of multiplicity distribution() from LMM equation. In particular, the equation for the average multiplicity of the color-singlet dipoles() turns out to be the homogeneous BFKL while at small . Second, using the diffusion approximation for the BFKL kernel we show that the factorial moments are equal to: which leads to the multiplicity distribution:. We also suggest a procedure for finding corrections to this multiplicity distribution which will be useful for descriptions of the experimental data.
Thi Nhung Dao🇻🇳 · Martin Gabelmann🇩🇪 · Margarete Mühlleitner🇩🇪 · Heidi Rzehak🇩🇪
We present our computation of the two-loop corrections to the Higgs boson masses of the CP-violating Next-to-Minimal Supersymmetric Standard Model (NMSSM) using the Feynman-diagrammatic approach in the gaugeless limit at vanishing external momentum. We choose a mixed -on-shell (OS) renormalisation scheme for the Higgs sector and apply both and OS renormalisation in the top/stop sector. For the treatment of the infrared divergences we apply and compare three different regularisation methods: the introduction of a regulator mass, the application of a small momentum expansion, and the inclusion of the full momentum dependence. Our new corrections have been implemented in the Fortran code NMSSMCALC that computes the Higgs mass spectrum of the CP-conserving and CP-violating NMSSM as well as the Higgs boson decays including the state-of-the-art higher-order corrections. Our numerical analysis shows that the newly computed corrections increase with rising and , remaining overall below about 3\% compared to our previously computed corrections, in the region compatible with perturbativity below the GUT scale. The renormalisation scheme and scale dependence is of typical two-loop order. The impact of the CP-violating phases in the new corrections is small. We furthermore show that the Goldstone Boson Catastrophe due to the infrared divergences can be treated in a numerically efficient way by introducing a regulator mass that approximates the momentum-dependent results best for squared mass values in the permille range of the squared renormalisation scale. Our results mark another step forward in the program of increasing the precision in the NMSSM Higgs boson observables.
H. Jung🇩🇪 · S. Taheri Monfared🇩🇪 · T. Wening🇩🇪
We present a complete set of transverse momentum dependent and collinear parton densities including the photon over a wide phase space. The photon density appears when evolving parton distributions with QED corrections. The photons are produced by perturbative radiation using the Parton Branching method. The QCD partons are constrained by a fit to HERA data. The lepton pair production at high masses is described within the extracted TMD densities.
Hong-Wei Ke🇨🇳 · Qing-Qing Kang🇨🇳 · Xiao-Hai Liu🇨🇳 · Xue-Qian Li🇨🇳
Without contamination from the final state interactions, the calculation of the branching ratios of semileptonic decays may provide us more information about the inner structure of charmed baryons. Moreover, by studying those processes, one can better determine the form factors of which can be further applied to relevant estimates. In this work, we use the light-front quark model to carry out the computations where the three-body vertex functions for and are employed. To fit the new data of the Belle II, we re-adjust the model parameters and obtain GeV which is 2.9 times larger than GeV. This value may imply that the pair in constitutes a more compact subsystem. Furthermore, we also investigate the non-leptonic decays of which will be experimentally measured soon, so our model would be tested by consistency with the new data.
Jie Ren🇨🇳 · Daohan Wang🇨🇳 · Lei Wu🇨🇳 · Jin Min Yang🇨🇳 · Mengchao Zhang🇨🇳
Axion-like particles (ALPs) appear in various new physics models with spontaneous global symmetry breaking. When the ALP mass is in the range of MeV to GeV, the cosmology and astrophysics bounds are so far quite weak. In this work, we investigate such light ALPs through the ALP-strahlung production processes with the sequential decay at the 14 TeV LHC with an integrated luminosity of 3000 fb (HL-LHC). Building on the concept of jet image which uses calorimeter towers as the pixels of the image and measures a jet as an image, we investigate the potential of machine learning techniques based on convolutional neural network (CNN) to identify the highly boosted ALPs which decay to a pair of highly collimated photons. With the CNN tagging algorithm, we demonstrate that our approach can extend current LHC sensitivity and probe the ALP mass range from 0.3~GeV to 5~GeV. The obtained bounds are stronger than the existing limits on the ALP-photon coupling.
Shao-Ping Li🇨🇳 · Xin-Qiang Li🇨🇳 · Xin-Shuai Yan🇨🇳 · Ya-Dong Yang🇨🇳
We provide a simple analysis of the big-bang nucleosynthesis (BBN) sensitivity to the light dark matter (DM) generated by the thermal freeze-in mechanism. It is shown that the ratio of the effective neutrino number shift over the DM relic density , denoted by , cancels the decaying particle mass and the feeble coupling, rendering therefore a simple visualization of at the BBN epoch in terms of the DM mass. This property drives one to conclude that the shift with a sensitivity of cannot originate from a single warm DM under the Lyman- forest constraints. For the cold-plus-warm DM scenarios where the Lyman- constraints are diluted, the ratio can be potentially used to test the thermal freeze-in mechanism in generating a small warm component of DM and a possible excess at the level of .
The article discusses a scenario based on the idea of induced spontaneous symmetry breaking. In this type of scenario, spontaneous symmetry breaking is assumed at some highest energy level, which leads to a chain of several subsequent induced symmetry violations at lower levels caused by small mixtures between levels. We present a simple model in which the idea is realized by small mixing between levels using scalar portals. In this approach, the large difference between energy scales, for example the Planck scale and the electroweak scale, occurs due to the product of several small factors proportional to the mixing coefficients. Dark matter fields can be formed in this scenario from matter fields on one or possibly several intermediate levels between the highest and lowest.
Takeo Inami🇯🇵 · Takahiro Kubota🇯🇵
The flavor-changing gravitational process d --> s + graviton, is evaluated at the one-loop level in the standard electroweak theory with on-shell renormalization. The results we present in the 't Hooft-Feynman gauge are valid for on- and off-shell quarks and for all external and internal quark masses. We show that there exist non-decoupling effects of the internal heavy top quark in interactions with gravity. A naive argument taking account of the quark Yukawa coupling suggests that the amplitude of the process d --> s + graviton in the large top quark mass limit would possibly acquire an enhancement factor , where and are the top quark and the W-boson masses, respectively. In practice this leading enhancement is absent in the renormalized amplitude due to cancellation. Thus the non-decoupling of the internal top quark takes place at the level. The flavor-changing two- and three-point functions are shown to satisfy the Ward-Takahashi identity, which is used for a consistency-check of the aforementioned cancellation of the terms. Among the non-decoupling terms, we sort out those that can be regarded as due to the effective Lagrangian in which quark bilinear forms are coupled to the scalar curvature.
Shu-Yi Kong🇨🇳 · Jun-Tao Zhu🇨🇳 · Dan Song🇨🇳 · Jun He🇨🇳
In this work, we systematically investigate the heavy-strange meson systems, and , to study possible molecules in a quasipotenial Bethe-Salpter equation approach together with the one-boson exchange model. The potential is achieved with the help of the hidden-gauge Lagrangians. Molecular states are found from all six -wave isoscalar interactions of or . The charmed-strange mesons and can be related to the and states with spin parities and , respectively. In the current model, the molecular state with is the best candidate of the recent observed . Four molecular states are produced from the interactions of or . The relation between the molecular state with and the is also discussed. No isovector molecular states are found from the interactions considered. The current results are helpful to understand the internal structure of , , , and new states. The experimental research for more heavy-strange meson molecules is suggested.
M. Miskaoui🇲🇦 · M. A. Loualidi🇲🇦
We propose a model of fermion masses and mixings based on grand unified theory (GUT) and a flavor symmetry. This is a highly predictive 4D GUT with a flavor symmetry that does not contain a triplet irreducible representation. The Yukawa matrices of quarks and charged leptons are obtained after integrating out heavy messenger fields from renormalizable superpotentials while neutrino masses originate from the type I seesaw mechanism. The group theoretical factors from 24- and 45-dimensional Higgs fields lead to ratios between the Yukawa couplings in agreement with data, while the dangerous proton decay operators are highly suppressed. By performing a numerical fit, we find that the model captures accurately the mixing angles, the Yukawa couplings and the phase of the quark sector at the GUT scale. The neutrino masses are generated at the renormalizable level with the prediction of trimaximal mixing while an additional effective operator is required to account for the baryon asymmetry of the universe (BAU). The model is remarkably predictive because only the normal neutrino mass ordering and the lower octant of the atmospheric angle are allowed while the conserving values of the Dirac neutrino phase are excluded. Moreover, the predicted values of the effective Majorana mass can be tested at future neutrinoless double beta decay experiments. An analytical and a numerical study of the BAU via the leptogenesis mechanism is performed. We focused on the regions of parameter space where leptogenesis from the lightest right-handed neutrino is successfully realized. Strong correlations between the parameters of the neutrino sector and the observed BAU are obtained.
Yosuke Takubo🇯🇵 · Tsubasa Ichikawa🇯🇵 · Satoshi Higashino🇯🇵 · Yuichiro Mori🇯🇵 · Kunihiro Nagano🇯🇵 · Izumi Tsutsui🇯🇵
We examine the feasibility of the Bell test (i.e., detecting a violation of the Bell inequality) with the ATLAS detector in Large Hadron Collider (LHC) at CERN through the flavor entanglement between the B mesons. After addressing the possible issues that arise associated with the experiment and how they may be treated based on an analogy with conventional Bell tests, we show in our simulation study that under realistic conditions (expected from the LHC Run 3 operation) the Bell test is feasible under mild assumptions. The definitive factor for this promising result lies primarily in the fact that the ATLAS detector is capable of measuring the decay times of the B mesons independently, which was not available in the previous experiment with the Belle detector at KEK. This result suggests the possibility of the Bell test in much higher energy domains and may open up a new arena for experimental studies of quantum foundations.
João Barata🇪🇸 · Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇫🇷 · Konrad Tywoniuk🇳🇴
We calculate the fully differential medium-induced radiative spectrum at next-to-leading order (NLO) accuracy within the Improved Opacity Expansion (IOE) framework. This scheme allows us to gain analytical control of the radiative spectrum at low and high gluon frequencies simultaneously. The high frequency regime can be obtained in the standard opacity expansion framework in which the resulting power series diverges at the characteristic frequency . In the IOE, all orders in opacity are resumed systematically below yielding an asymptotic series controlled by logarithmically suppressed remainders down to the thermal scale , while matching the opacity expansion at high frequency. Furthermore, we demonstrate that the IOE at NLO accuracy reproduces the characteristic Coulomb tail of the single hard scattering contribution as well as the Gaussian distribution resulting from multiple soft momentum exchanges. Finally, we compare our analytic scheme with a recent numerical solution, that includes a full resummation of multiple scatterings, for LHC-inspired medium parameters. We find a very good agreement both at low and high frequencies showcasing the performance of the IOE which provides for the first time accurate analytic formulas for radiative energy loss in the relevant perturbative kinematic regimes for dense media.
The existence of stable multiquarks made of heavy quarks and antiquarks is discussed in the framework of potential models. It is stressed that the few-body problem should be handled seriously and accurately. No bound state is found within the current models. But resonances are likely present in the spectrum above the lowest threshold.
Pulak Banerjee🇨🇭 · Tim Engel🇨🇭 · Nicolas Schalch🇨🇭 · Adrian Signer🇨🇭 · Yannick Ulrich🇬🇧
A critical subject in fully differential QED calculations originates from numerical instabilities due to small fermion masses that act as regulators of collinear singularities. At next-to-next-to-leading order (NNLO) a major challenge is therefore to find a stable implementation of numerically delicate real-virtual matrix elements. In the case of Bhabha scattering this has so far prevented the development of a fixed-order Monte Carlo at NNLO accuracy. In this paper we present a new method for stabilising the real-virtual matrix element. It is based on the expansion for soft photon energies including the non-universal subleading term calculated with the method of regions. We have applied this method to Bhabha scattering to obtain a stable and efficient implementation within the McMule framework. We therefore present for the first time fully differential results for the photonic NNLO corrections to Bhabha scattering.
Alex G. Dias🇧🇷 · Julio Leite🇧🇷 · Diego S. V. Gonçalves🇧🇷
We propose a gauged two-Higgs-doublet model (2HDM) featuring an anomalous Peccei-Quinn symmetry, . Dangerous tree-level flavour-changing neutral currents, common in 2HDMs, are forbidden by the extra gauge symmetry, . In our construction, the solutions to the important issues of neutrino masses, dark matter and the strong CP problem are interrelated. Neutrino masses are generated via a Dirac seesaw mechanism and are suppressed by the ratio of the and the breaking scales. Naturally small neutrino masses suggest that the breaking of occurs at a relatively low scale, which may lead to observable signals in near-future experiments. Interestingly, spontaneous symmetry breaking does not lead to mixing between the gauge boson, , and the standard . For the expected large values of the scale, the associated axion becomes "invisible", with DFSZ-like couplings, and may account for the observed abundance of cold dark matter. Moreover, a viable parameter space region, which falls within the expected sensitivities of forthcoming axion searches, is identified. We also observe that the flavour-violating process of kaon decaying into pion plus axion, , is further suppressed by the scale, providing a rather weak lower bound for the axion decay constant .
Arvind Bhaskar🇮🇳 · Tanumoy Mandal🇮🇳 · Subhadip Mitra🇮🇳 · Mohit Sharma🇮🇳
Search strategies for the third-generation leptoquarks (LQs) are distinct from other LQ searches, especially when they decay to a top quark and a lepton. We investigate the cases of all TeV-scale scalar and vector LQs that decay to either a top-tau pair (charge- and LQs) or a top-neutrino pair (charge- LQs). One can then use the boosted top (which can be tagged efficiently using jet-substructure techniques) and high- leptons to search for these LQs. We consider two search channels with either one or two taus along with at least one hadronically decaying boosted top quark. We estimate the high luminosity LHC (HL-LHC) search prospects of these LQs by considering both symmetric and asymmetric pair and single production processes. Our selection criteria are optimised to retain events from both pair and single production processes. The combined signal has better prospects than the traditional searches. We include new three-body single production processes to enhance the single production contributions to the combined signal. We identify the interference effect that appears in the dominant single production channel of charge- scalar LQ (). This interference is constructive if is weak-triplet and destructive, for a singlet one. As a result, their LHC prospects differ appreciably.
Himanshu Swami🇮🇳 · Kinjalk Lochan🇮🇳 · Ketan M. Patel🇮🇳
We study decoherence effects in neutrino flavour oscillations in curved spacetime with particular emphasis on the lensing in a Schwarzschild geometry. Assuming Gaussian wave packets for neutrinos, we argue that the decoherence length derived from the exponential suppression of the flavour transition amplitude depends on the proper time of the geodesic connecting the events of the production and detection in general gravitational setting. In the weak gravity limit, the proper time between two events of given proper distance is smaller than that in the flat spacetime. Therefore, in presence of a Schwarzschild object, the neutrino wave packets have to travel relatively more physical distance in space to lapse the same amount of proper time before they decoher. For non-radial propagation applicable to the lensing phenomena, we show that the decoherence, in general, is sensitive to the absolute values of neutrino masses as well as the classical trajectories taken by neutrinos between the source and detector along with the spatial widths of neutrino wave packets. At distances beyond the decoherence length, the probability of neutrino flavour transition due to lensing attains a value which depends only on the leptonic mixing parameters. Hence, the observability of neutrino lensing significantly depends on these parameters and in-turn the lensing can provide useful information about them.
Sebastian Baum🇺🇸 · Thomas D.P. Edwards🇸🇪 · Katherine Freese🇺🇸 · Patrick Stengel🇮🇹
Paleo-detectors are a proposed experimental technique to search for dark matter (DM). In lieu of the conventional approach of operating a tonne-scale real-time detector to search for DM-induced nuclear recoils, paleo-detectors take advantage of small samples of naturally occurring rocks on Earth that have been deep underground ( km), accumulating nuclear damage tracks from recoiling nuclei for Gyr. Modern microscopy techniques promise the capability to read out nuclear damage tracks with nanometer resolution in macroscopic samples. Thanks to their Gyr integration times, paleo-detectors could constitute nuclear recoil detectors with keV recoil energy thresholds and 100 kilotonne-yr exposures. This combination would allow paleo-detectors to probe DM-nucleon cross sections orders of magnitude below existing upper limits from conventional direct detection experiments. In this article, we use improved background modeling and a new spectral analysis technique to update the sensitivity forecast for paleo-detectors. We demonstrate the robustness of the sensitivity forecast to the (lack of) ancillary measurements of the age of the samples and the parameters controlling the backgrounds, systematic mismodeling of the spectral shape of the backgrounds, and the radiopurity of the mineral samples. Specifically, we demonstrate that even if the uranium concentration in paleo-detector samples is (per weight), many orders of magnitude larger than what we expect in the most radiopure samples obtained from ultra basic rock or marine evaporite deposits, paleo-detectors could still probe DM-nucleon cross sections below current limits. For DM masses GeV/, the sensitivity of paleo-detectors could still reach down all the way to the conventional neutrino floor in a Xe-based direct detection experiment.
We discuss stiffening of matter in quark-hadron continuity. We introduce a model that relates quark wave functions in a baryon and the occupation probability of states for baryons and quarks in dense matter. In a dilute regime, the confined quarks contribute to the energy density through the masses of baryons, but do not directly contribute to the pressure; hence, the equations of state are very soft. This dilute regime continues until the low momentum states for quarks get saturated; this may happen even before baryons fully overlap, possibly at density slightly above the nuclear saturation density. After the saturation the pressure grows rapidly while changes in energy density are modest, producing a peak in the speed of sound. If we use baryonic descriptions for quark distributions near the Fermi surface, we reach a description similar to the quarkyonic matter model of McLerran and Reddy. With a simple adjustment of quark interactions to get the nucleon mass, our model becomes consistent with the constraints from 1.4-solar mass neutron stars, but the high density part is too soft to account for two-solar mass neutron stars. We delineate the relation between the saturation effects and short range interactions of quarks, suggesting interactions that leave low density equations of state unchanged but stiffen the high density part.
Nicolò Oreste Pinciroli Vago🇳🇴 · Ibrahim A. Hameed🇳🇴 · Michael Kachelriess🇳🇴
The presence of non-zero helicity in intergalactic magnetic fields is a smoking gun for their primordial origin since they have to be generated by processes that break CP invariance. As an experimental signature for the presence of helical magnetic fields, an estimator based on the triple scalar product of the wave-vectors of photons generated in electromagnetic cascades from, e.g., TeV blazars, has been suggested previously. We propose to apply deep learning to helicity classification employing Convolutional Neural Networks and show that this method outperforms the estimator.
Alex Keshavarzi🇬🇧 · Kim Siang Khaw🇨🇳 · Tamaki Yoshioka🇯🇵
The muon magnetic anomaly, , plays a special role in the history of the Standard Model (SM). Precise calculations and measurements of this fundamental quantity provide a stringent test of the SM and a window to the physics beyond. In light of the first result published by the Fermilab Muon experiment, this article reviews the current status of the experimental measurement and theoretical prediction of the muon anomalous magnetic moment. It also provides an overview on resulting constraints of associated physics beyond the SM (BSM), future muon experiments, and on the progress of experiments that are closely connected to the physics of the muon , such as measurements that could provide complementary information about BSM physics in the muon sector.
Srinikitha Bhagvati🇮🇳 · Shantanu Desai🇮🇳
We implement a test of the variability of the per-cycle annual modulation amplitude in the different phases of the DAMA/LIBRA experiment using Bayesian model comparison. Using frequentist methods, a previous study (Kelso et al 2018) had demonstrated that the DAMA amplitudes spanning over the DAMA/NaI and the first phase of the DAMA/LIBRA phases, show a mild preference for time-dependence in multiple energy bins. With that motivation, we first show using Bayesian techniques that the aforementioned data analyzed in Kelso et al, show a moderate preference for exponentially varying amplitudes in the 2-5 and 2-6 keV energy intervals. We then carry out a similar analysis on the latest modulation amplitudes released by the DAMA collaboration from the first two phases of the upgraded DAMA/LIBRA experiment. We also analyze the single-hit residual rates released by the DAMA collaboration to further look for any possible time-dependency. However, we do not find any evidence for variability of either of the two datasets by using Bayesian model selection. All our analysis codes and datasets have been made publicly available.
A.C Hayes🇺🇸 · J.L. Friar🇺🇸 · GM. Hale🇺🇸 · GT. Garvey🇺🇸
Motivated by the recent observation of anomalous electron-positron angular correlations in the decay of the 18.15 MeV 1+ excited states in 8Be, we reexamine in detail the Standard Model expectations for these angular correlations. The 18.15 MeV state is above particle threshold, and several multipoles can contribute to its decay. We present the general theoretical expressions for angular distributions for nuclear decay by C0, C1, C2 M1, E1, and E2 multipoles, and we examine their relative contribution to the decay of 8Be at 18.15 MeV. We find that this resonance is dominated by M1 and E1 decay, and that the ratio of M1 to E1 strength is a strong function of energy. This is in contract to the original analysis of the angular distributions, where the M1/E1 ratio was assumed to be a constant over the energy region Ep = 0:8-1:2 MeV. We find that the existence of a `bump' in the measured angular distribution is strongly dependent on the assumed M1/E1 ratio, with the present analysis finding the measured large-angle contributions to the angular distribution to be lower than expectation. Thus, in the current analysis we find no evidence for axion decay in the 18.15 MeV resonance region of 8Be.
Nikolai Korchagin🇨🇳 · Andrey Radzhabov🇷🇺
The effect of axial meson exchange on extraction of proton electromagnetic form factors in scattering is calculated. Taking as an example meson exchange, it is quantitatively shown how it affects Rosenbluth and polarization transfer methods. The contribution of an axial meson is negligible in comparison with the traditional box-type two photon exchange and could not be responsible for difference of form factors extracted by different techniques. However, results support the idea that meson exchange could explain deviation of individual polarizations.
Mateusz Cierniak🇵🇱 · David Blaschke🇵🇱
We present a systematic investigation of the possible locations for the special point (SP), a unique feature of hybrid neutron stars in the mass-radius. The study is performed within the two-phase approach where the high-density (quark matter) phase is described by the constant-sound-speed (CSS) equation of state (EoS) and the nuclear matter phase around saturation density is varied from very soft (APR) to stiff (DD2 with excluded nucleon volume. Different construction schemes for the deconfinement transition are applied: Maxwell construction, mixed phase construction and parabolic interpolation. We demonstrate for the first time that the SP is invariant not only against changing the nuclear matter EoS, but also against variation of the construction schemes for the phase transition. Since the SP serves as a proxy for the maximum mass and accessible radii of massive hybrid stars, we draw conclusions for the limiting masses and radii of hybrid neutron stars.
Elisa Maggio🇮🇹 · Maarten van de Meent🇩🇪 · Paolo Pani🇮🇹
Extreme mass-ratio inspirals (EMRIs) detectable by the Laser Interferometer Space Antenna are unique probes of the nature of supermassive compact objects. We compute the gravitational-wave signal emitted by a stellar-mass compact object in a circular equatorial orbit around a Kerr-like horizonless supermassive object defined by an effective radius and a reflectivity coefficient. The Teukolsky equations are solved consistently with suitable (frequency-dependent) boundary conditions, and the modified energy and angular-momentum fluxes are used to evolve the orbital parameters adiabatically. The gravitational fluxes have resonances corresponding to the low-frequency quasinormal modes of the central object, which can contribute significantly to the gravitational-wave phase. Overall, the absence of a classical event horizon in the central object can affect the gravitational-wave signal dramatically, with deviations even larger than those previously estimated by a model-independent analysis of the tidal heating. We estimate that EMRIs could potentially place the most stringent constraint on the reflectivity of supermassive compact objects at the remarkable level of and would allow to constrain various models which are not ruled out by the ergoregion instability. In particular, an EMRI detection could allow one to rule out (or provide evidence for) signatures of quantum black-hole horizons with Boltzmann reflectivity. Our results provide motivation for performing rigorous parameter estimation to assess the detectability of these effects.
Bum-Hoon Lee🇰🇷 · Wonwoo Lee🇰🇷 · Dong-han Yeom🇰🇷 · Lu Yin🇰🇷
We investigate the gravitational wave spectrum resulted from the cosmological first-order phase transition. We compare two models; one is a scalar field model without gravitation, while the other is a scalar field model with gravitation. Based on the sensitivity curves of the LISA space-based interferometer on the stochastic gravitational-wave background, we compare the difference between the gravitational wave spectra of the former and the latter cases resulted from the bubble collision process. Especially, we calculated the speed of the bubble wall before collision for the two models numerically. We show that the difference between the amplitudes of those spectra can clearly distinguish between the two models. We expect that the LISA with Signal to Noise Ratio =10 could observe the spectrum as the fast first-order phase transition.
Mathieu Boudaud🇪🇸 · Thomas Lacroix🇪🇸 · Martin Stref🇫🇷 · Julien Lavalle🇫🇷 · Pierre Salati🇫🇷
Primordial black holes may have been produced in the early stages of the thermal history of the Universe after cosmic inflation. If so, dark matter in the form of elementary particles can be subsequently accreted around these objects, in particular when it gets non-relativistic and further streams freely in the primordial plasma. A dark matter mini-spike builds up gradually around each black hole, with density orders of magnitude larger than the cosmological one. We improve upon previous work by carefully inspecting the computation of the mini-spike radial profile as a function of black hole mass, dark matter particle mass and temperature of kinetic decoupling. We identify a phase-space contribution that has been overlooked and that leads to changes in the final results. We also derive complementary analytical formulae using convenient asymptotic regimes, which allows us to bring out peculiar power-law behaviors for which we provide tentative physical explanations.
Matteo Braglia🇪🇸 · Xingang Chen🇺🇸 · Dhiraj Kumar Hazra🇮🇳
We propose an inflationary primordial feature model that can explain both the large and small-scale anomalies in the currently measured cosmic microwave background (CMB) anisotropy spectra, revealing a clip of adventurous history of the Universe during its primordial epoch. Although the model is currently statistically indistinguishable from the Standard Model, we show that future observations such as the Simons Observatory and LiteBIRD will complement each other in distinguishing the model differences due to their accurate E-mode polarization measurements, and the PICO mission, if funded, can put stringent constraints on all characteristic properties. The model predicts a signal of classical primordial standard clock, which can also be used to distinguish the inflation and alternative scenarios in a model-independent fashion.
Igor Bandos🇪🇸 · Kurt Lechner🇮🇹 · Dmitri Sorokin🇮🇹 · Paul K. Townsend🇬🇧
We give a prescription for N=1 supersymmetrization of any (four-dimensional) nonlinear electrodynamics theory with a Lagrangian density satisfying a convexity condition that we relate to semi-classical unitarity. We apply it to the one-parameter ModMax extension of Maxwell electrodynamics that preserves both electromagnetic duality and conformal invariance, and its Born-Infeld-like generalization, proving that duality invariance is preserved. We also establish superconformal invariance of the superModMax theory by showing that its coupling to supergravity is super-Weyl invariant. The higher-derivative photino-field interactions that appear in any supersymmetric nonlinear electrodynamics theory are removed by an invertible nonlinear superfield redefinition.
Miguel Montero🇺🇸 · Cumrun Vafa🇺🇸 · Thomas Van Riet🇧🇪 · Victoria Venken🇩🇪
Demanding that charged Nariai black holes in (quasi-)de Sitter space decay without becoming super-extremal implies a lower bound on the masses of charged particles, known as the Festina Lente (FL) bound. In this paper we fix the constant in the bound and elucidate various aspects of it, as well as extensions to and to situations with scalar potentials and dilatonic couplings. We also discuss phenomenological implications of FL including an explanation of why the Higgs potential cannot have a local minimum at the origin, thus explaining why the weak force must be broken. For constructions of meta-stable dS involving anti-brane uplift scenarios, even though the throat region is consistent with FL, the bound implies that we cannot have any light charged matter fields coming from any far away region in the compactified geometry, contrary to the fact that they are typically expected to arise in these scenarios. This strongly suggests that introduction of warped anti-branes in the throat cannot be decoupled from the bulk dynamics as is commonly assumed. Finally, we provide some evidence that in certain situations the FL bound can have implications even with gravity decoupled and illustrate this in the context of non-compact throats.
* 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.