Fri·Jul 5, 2019Friday·July 5, 2019

1. 01*

   Sampling the $\mu \nu$SSM for displaced decays of the tau left sneutrino LSP at the LHC

   Essodjolo Kpatcha🇪🇸 · Inaki Lara🇪🇸 · Daniel E. Lopez-Fogliani🇦🇷 · Carlos Munoz🇪🇸 · Natsumi Nagata🇯🇵 · Hidetoshi Otono🇯🇵 · Roberto Ruiz de Austri🇪🇸

   Within the framework of the $\mu \nu$SSM, a displaced dilepton signal is expected at the LHC from the decay of a tau left sneutrino as the lightest supersymmetric particle (LSP) with a mass in the range $45-100$ GeV. We compare the predictions of this scenario with the ATLAS search for long-lived particles using displaced lepton pairs in $pp$ collisions, considering an optimization of the trigger requirements by means of a high level trigger that exploits tracker information. The analysis is carried out in the general case of three families of right-handed neutrino superfields, where all the neutrinos get contributions to their masses at tree level. To analyze the parameter space, we sample the $\mu \nu$SSM for a tau left sneutrino LSP with proper decay length $c\tau >0.1$ mm using a likelihood data-driven method, and paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavor observables. The sneutrino is special in the $\mu \nu$SSM since its couplings have to be chosen so that the neutrino oscillation data are reproduced. We find that important regions of the parameter space can be probed at the LHC run 3.

   hep-phhep-exEPJC(2019)·20 citations
2. 02*

   Preserving physically important variables in optimal event selections: A case study in Higgs physics

   Philipp Windischhofer🇬🇧 · Miha Zgubic🇬🇧 · Daniela Bortoletto🇬🇧

   Analyses of collider data, often assisted by modern Machine Learning methods, condense a number of observables into a few powerful discriminants for the separation of the targeted signal process from the contributing backgrounds. These discriminants are highly correlated with important physical observables; using them in the event selection thus leads to the distortion of physically relevant distributions. We present a novel method based on a differentiable estimate of mutual information, a measure of non-linear dependency between variables, to construct a discriminant that is statistically independent of a number of selected observables, and so manages to preserve their distributions in the event selection. Our strategy is evaluated in a realistic setting, the analysis of the Standard Model Higgs boson decaying into a pair of bottom quarks. Using the distribution of the invariant mass of the di-b-jet system to extract the Higgs boson signal strength, our method achieves state-of-the-art performance compared to other decorrelation techniques, while significantly improving the sensitivity of a similar, cut-based, analysis published by ATLAS.

   hep-phcs.LGJHEP(2020)·17 citations
3. 03*

   Hadron resonance gas with repulsive mean field interaction: Thermodynamics and transport properties

   Guruprasad Kadam🇮🇳 · Hiranmaya Mishra🇮🇳

   We discuss the interacting hadron resonance gas model to describe the thermodynamics of hadronic matter. While the attractive interaction between hadrons is taken care of by including all the resonances with zero width, the repulsive interactions are included by considering density-dependent mean field potentials. The bulk thermodynamic quantities are confronted with the lattice quantum chromodynamics simulation results at zero as well as at finite baryon chemical potential. We further estimate the shear and bulk viscosity coefficients of hot and dense hadronic matter within the ambit of this interacting hadron resonance gas model.

   hep-phnucl-thPRD(2019)·13 citations
4. 04*

   Deformed QCD phase structure and entropy oscillation in the presence of a magnetic background

   Guo-yun Shao🇨🇳 · Wei-bo He🇨🇳 · Xue-yan Gao🇨🇳

   The QCD phase transitions are investigated in the presence of an external magnetic field in the Polyakov improved Nambu--Jona-Lasinio (PNJL) model. We detailedly analyze that how the filling of multiple Landau levels by light (up and down) quarks deforms the QCD phase structure under different magnetic fields. In particular, we concentrate on the phase transition under a magnetic field possibly reachable in the non-central heavy-ion collisions at RHIC. The numerical result shows that two first-order transitions or more complicate phase transition in the light quark sector can exist for some magnetic fields, different from the phase structure under a very strong or zero magnetic field. These phenomena are very interesting and possibly relevant to the non-central heavy-ion collision experiments with colliding energies at several $A$ GeV as well as the equation of state of magnetars. Besides, we investigate the entropy oscillation with the increase of baryon density in a magnetic background.

   hep-phPRD(2019)·13 citations
5. 05*

   Testing fifth forces from the Galactic dark matter

   Lijing Shao🇨🇳

   Is there an unknown long-range force between dark matter (DM) and ordinary matters? When such a fifth force exists and in the case that it is ignored, the equivalence principle (EP) is violated apparently. The violation of EP was severely constrained by, for examples, the Eöt-Wash laboratory experiments, the lunar laser ranging, the MICROSCOPE satellite, and the long-term observation of binary pulsars. We discuss a recent bound that comes from PSR J1713+0747. When it is combined with the other bounds, a compelling limit on the hypothetical fifth force is derived. For the neutral hydrogen, the strength of such a fifth force should not exceed $1\%$ of the gravity.

   hep-phastro-ph.HEMDPI Proc.(2019)·1 citation
6. 06*

   Lepton Flavor Universality tests through angular observables of $\overline{B}\to D^{(\ast )}\ell \overline{\nu }$ decay modes

   Damir Becirevic🇫🇷 · Marco Fedele🇪🇸 · Ivan Nisandzic🇩🇪 · Andrey Tayduganov🇩🇪

   We discuss the possibility of using the observables deduced from the angular distribution of the $B\to D^{(\ast )}\ell \bar{\nu }$ decays to test the effects of lepton flavor universality violation (LFUV). We show that the measurement of even a subset of these observables could be very helpful in distinguishing the Lorentz structure of the New Physics contributions to these decays. To do so we use the low energy effective theory in which besides the Standard Model contribution we add all possible Lorentz structures with the couplings (Wilson coefficients) that are determined by matching theory with the measured ratios $R{(D^{(\ast )})}^{\exp }$. We argue that even in the situation in which the measured $R{(D^{(\ast )})}^{\exp }$ becomes fully compatible with the Standard Model, one can still have significant New Physics contributions the size of which could be probed by measuring the observables discussed in this paper and comparing them with their Standard Model predictions.

   hep-phhep-ex81 citations
7. 07*

   Uncertainty in the Reactor Neutrino Spectrum and Mass Hierarchy Determination

   Emilio Ciuffoli🇨🇳 · Jarah Evslin🇨🇳 · Hosam Mohammed🇨🇳

   One of the challenges that must be overcome in order to determine the neutrino mass hierarchy using reactor neutrinos is the theoretical uncertainty in the unoscillated reactor neutrino spectrum: this is one of the reasons why, recently, it was proposed to add a near detector to the JUNO experiment. A model-independent treatment of the spectrum uncertainty will be discussed, as well as the effect that it will have on the final result. Moreover, since the neutrino spectrum depends on the chemical composition of the fuel, the spectra at the near and far detectors will be different, because they will receive neutrinos from different cores. Taking into account the time evolution of the chemical composition of the fuel in the reactor core, it is possible to reconstruct the far detector spectrum from the near detector data. We will show that the method used to reconstruct the spectrum can affect sensitivity to the mass hierarchy, however if the near detector is large enough the difference will be negligible.

   hep-phJHEP(2019)·4 citations
8. 08*

   Low-virtuality photon transitions ${\gamma }^{\ast }\to f\bar{f}$ and the photon-to-jet conversion function

   Ansgar Denner🇩🇪 · Stefan Dittmaier🇩🇪 · Mathieu Pellen🇬🇧 · Christopher Schwan🇮🇹

   The calculation of electroweak corrections to processes with jets in the final state involves contributions of low-virtuality photons leading to jets in the final state via the singular splitting ${\gamma }^{\ast }\to q\bar{q}$. These singularities can be absorbed into a photon-to-jet "fragmentation function", better called "conversion function", since the physical final state is any hadronic activity rather than an identified hadron. Using unitarity and a dispersion relation, we relate this ${\gamma }^{\ast }\to q\bar{q}$ conversion contribution to an integral over the imaginary part of the hadronic vacuum polarization and thus to the experimentally known quantity $\Delta {\alpha }_{\mathrm{had}}^{(5)}(M_{\mathrm{Z}}^2)$. Therefore no unknown non-perturbative contribution remains that has to be taken from experiment. We also describe practical procedures following subtraction and phase-space-slicing approaches for isolating and cancelling the ${\gamma }^{\ast }\to q\bar{q}$ singularities against the photon-to-jet conversion function. The production of Z+jet at the LHC is considered as an example, where the photon-to-jet conversion is part of a correction of the order ${\alpha }^2/{\alpha }_{\mathrm{s}}$ relative to the leading-order cross section.

   hep-phPLB(2019)·28 citations
9. 09*

   Circularly Polarized Gamma Rays in Effective Dark Matter Theory

   Wei-Chih Huang🇩🇰 · Kin-Wang Ng🇹🇼 · Tzu-Chiang Yuan🇹🇼

   We study the loop-induced circularly polarized gamma rays from dark matter annihilation using the effective dark matter theory approach. Both neutral scalar and fermionic dark matter annihilating into monochromatic diphoton and $Z$-photon final states are considered. To generate the circular polarization asymmetry, $P$ and $CP$ symmetries must be violated in the couplings between dark matter and Standard Model fermions inside the loop with non-vanishing Cutkosky cut. The asymmetry can be sizable especially for $Z$-photon final state for which asymmetry of nearly $90\%$ can be reached. We discuss the prospect for detecting the circular polarization asymmetry of the gamma-ray flux from dark matter annihilation in the Galactic Center in future gamma-ray polarimetry experiments.

   hep-phastro-ph.HEPLB(2020)·7 citations
10. 10*

    Simple Gradient Flow Equation for the Bounce Solution

    Ryosuke Sato🇩🇪

    Motivated by the recent work of Chigusa, Moroi, and Shoji, we propose a new simple gradient flow equation to derive the bounce solution which contributes to the decay of the false vacuum. Our discussion utilizes the discussion of Coleman, Glaser, and Martin and we solve a minimization problem of the kinetic energy while fixing the potential energy. The bounce solution is derived as a scale-transformed of the solution of this problem. We also show that the convergence of our method is robust against a choice of the initial configuration.

    hep-phastro-ph.COhep-thmath-ph+1PRD(2020)·25 citations
11. 11*

    Matter Power Spectrum of Light Freeze-in Dark Matter: With or without Self-Interaction

    Ran Huo🇺🇸

    We study the free-streaming effect in a light freeze-in dark matter model. Naturally in the dark sector one can find dark matter related coupling, and such coupling may induce dark matter self-scattering. In case that such scattering is subdominant, the dark matter partition function is not thermal but determined by the freeze-in process, yet its high momentum side is generally also Boltzmann suppressed. We show that the matter power spectrum is very similar to a warm dark matter one in shape. When matched to the current WDM bound, a $24$~keV freeze-in dark matter is ruled out at $2\sigma$ confidence level. In case that the dark matter self-scattering is strong and decouples at a very late time, by a new numerical calculation we show that the early stage Brownian motion indeed protects the power spectrum against free-streaming suppression. However, such an effect cannot be characterized by a free-streaming length alone; we find that the self-scattering decoupling time is another necessary parameter. The currently interested dark matter self-interaction cross section $\sim {\text{cm}}^2/\text{g}$ is just marginal for such protection to be effective.

    hep-phPLB(2020)·20 citations
12. 12*

    The Lorentz- and CPT-Violating Standard Model Extension in Chiral Perturbation Theory

    Brett Altschul🇺🇸 · Matthias R. Schindler🇺🇸

    Lorentz and CPT violation in hadronic physics must be tied to symmetry violations at the underlying quark and gluon level. Chiral perturbation theory provides a method for translating novel operators that may appear in the Lagrange density for color-charged parton fields into equivalent forms for effective theories at the meson and baryon levels. We extend the application of this technique to the study of Lorentz-violating and potentially CPT-violating operators from the minimal standard model extension. For dimension-4 operators, there are nontrivial relations between the coefficients of baryon-level operators related to underlying quark and gluon operators with the same Lorentz structures. Moreover, in the mapping of the dimension-3 operators from the quark and gluon level to the hadron level (considered here for the first time), many of the hadronic observables contain no new low-energy coupling constants at all, which makes it possible to make direct translations of bounds derived using experiments on one kind of hadron into bounds in a completely different corner of the hadronic sector. A notable consequence of this is bounds (at $10^{-15}$-$10^{-20}$ GeV levels) on differences $a_B^{\mu }-a_{B^{\prime }}^{\mu }$ of Lorentz and CPT violation coefficients for $SU(3{)}_f$ octet baryons that differ in their structure by the replacement of a single valance $d$ quark by a $s$ quark. Never before has there been any proposal for how these kinds of differences could be constrained.

    hep-phhep-thPRD(2019)·17 citations
13. 13*

    Standard Model parameters in the tadpole-free pure $\overline{\mathrm{MS}}$ scheme

    Stephen P. Martin🇺🇸 · David G. Robertson🇺🇸

    We present an implementation and numerical study of the Standard Model couplings, masses, and vacuum expectation value (VEV), using the pure $\overline{\mathrm{MS}}$ renormalization scheme based on dimensional regularization. Here, the $\overline{\mathrm{MS}}$ Lagrangian parameters are treated as the fundamental inputs, and the VEV is defined as the minimum of the Landau gauge effective potential, so that tadpole diagrams vanish, resulting in improved convergence of perturbation theory. State-of-the-art calculations relating the $\overline{\mathrm{MS}}$ inputs to on-shell observables are implemented in a consistent way within a public computer code library, SMDR (Standard Model in Dimensional Regularization), which can be run interactively or called by other programs. Included here for the first time are the full 2-loop contributions to the Fermi constant within this scheme and studies of the minimization condition for the VEV at 3-loop order with 4-loop QCD effects. We also implement, and study the scale dependence of, all known multi-loop contributions to the physical masses of the Higgs boson, the W and Z bosons, and the top quark, the fine structure constant and weak mixing angle, and the renormalization group equations and threshold matching relations for the gauge couplings, fermion masses, and Yukawa couplings.

    hep-phPRD(2019)·46 citations
14. 14*

    Eigenvalues: the Rosetta Stone for Neutrino Oscillations in Matter

    Peter B. Denton🇺🇸 · Stephen J. Parke🇺🇸 · Xining Zhang🇺🇸

    We present a new method of exactly calculating neutrino oscillation probabilities in matter. We leverage the "eigenvector-eigenvalue identity" to show that, given the eigenvalues, all mixing angles in matter follow surprisingly simply. The CP violating phase in matter can then be determined from the Toshev identity. Then, to avoid the cumbersome expressions for the exact eigenvalues, we have applied previously derived perturbative, approximate eigenvalues to this scheme and discovered them to be even more precise than previously realized. We also find that these eigenvalues converge at a rate of five orders of magnitude per perturbative order which is the square of the previously realized expectation. Finally, we provide an updated speed versus accuracy plot for oscillation probabilities in matter, to include the methods of this paper.

    hep-phPRD(2020)·42 citations
15. 15*

    Accessible Lepton-Number-Violating Models and Negligible Neutrino Masses

    André de Gouvêa🇺🇸 · Wei-Chih Huang🇩🇰 · Johannes König🇩🇰 · Manibrata Sen🇺🇸

    Lepton-number violation (LNV), in general, implies nonzero Majorana masses for the Standard Model neutrinos. Since neutrino masses are very small, for generic candidate models of the physics responsible for LNV, the rates for almost all experimentally accessible LNV observables -- except for neutrinoless double-beta decay -- are expected to be exceedingly small. Guided by effective-operator considerations of LNV phenomena, we identify a complete family of models where lepton number is violated but the generated Majorana neutrino masses are tiny, even if the new-physics scale is below 1 TeV. We explore the phenomenology of these models, including charged-lepton flavor-violating phenomena and baryon-number-violating phenomena, identifying scenarios where the allowed rates for ${\mu }^{-}\to e^{+}$-conversion in nuclei are potentially accessible to next-generation experiments.

    hep-phPRD(2019)·17 citations
16. 16*

    Variation in the fine-structure constant, distance-duality relation and the next generation of high-resolution spectrograph

    Rodrigo S. Gonçalves🇧🇷 · Susana Landau🇦🇷 · Jailson S. Alcaniz🇧🇷 · Rodrigo F. L. Holanda🇧🇷

    The possibility of variation of the fundamental constants of nature has been a long-standing question, with important consequences for fundamental physics and cosmology. In particular, it has been shown that variations in the fine-structure constant, $\alpha$, are directly related to violation of the distance duality relation (DDR), which holds true as long as photons travel on unique null geodesics and their number is conserved. In this paper we use the currently available measurements of $\Delta \alpha /\alpha$ to impose the most stringent constraints on departures of the DDR to date, here quantified by the parameter $\eta$. We also perform a forecast analysis to discuss the ability of the new generation of high-resolution spectrograph, like ESPRESSO/VLT and E-ELT-HIRES, to constrain the DDR parameter $\eta$. From the current data we obtain constraints on $\eta$ of the order of $10^{-7}$ whereas the forecasted constraints are two orders of magnitude lower. Considering the expected level of uncertainties of the upcoming measurements, we also estimate the necessary number of data points to confirm the hypotheses behind the DDR.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·23 citations
17. 17*

    Motion induced radiation and quantum friction for a moving atom

    M. Belen Farias🇦🇷 · C. D. Fosco🇦🇷 · Fernando C. Lombardo🇦🇷 · Francisco D. Mazzitelli🇦🇷

    We study quantum dissipative effects that result from the non-relativistic motion of an atom, coupled to a quantum real scalar field, in the presence of a static imperfect mirror. Our study consists of two parts: in the first, we consider accelerated motion in free space, namely, switching off the coupling to the mirror. This results in motion induced radiation, which we quantify via the vacuum persistence amplitude. In the model we use, the atom is described by a quantum harmonic oscillator (QHO). We show that its natural frequency poses a threshold which separates different regimes, involving or not the internal excitation of the oscillator, with the ulterior emission of a photon. At higher orders in the coupling to the field, pairs of photons may be created by virtue of the Dynamical Casimir Effect (DCE). In the second part, we switch on the coupling to the mirror, which we describe by localized microscopic degrees of freedom. We show that this leads to the existence of quantum contactless friction as well as to corrections to the free space emission considered in the first part. The latter are similar to the effect of a dielectric on the spontaneous emission of an excited atom. We have found that, when the atom is accelerated and close to the plate, it is crucial to take into account the losses in the dielectric in order to obtain finite results for the vacuum persistence amplitude.

    ↳ quant-phcond-mat.otherhep-phPRD(2019)·25 citations
18. 18*

    Testing Lorentz violation by the comparison of atomic clocks

    Xiao-yu Lu🇨🇳 · Yu-Jie Tan🇨🇳 · Cheng-Gang Shao🇨🇳

    A more complete theoretical model of testing Lorentz violation by the comparison of atomic clocks is developed in the Robertson-Mansouri-Sexl kinematic framework. As this frame postulates the deviation of the coordinate transformation from the Lorentz transformation, from the viewpoint of the transformation violations on time and space, the LI violating effect in the atomic clock comparison can be explained as two parts: time-delay effect $\alpha \frac{v^2}{c^2}$ and structure effect $-\frac{\beta +2\delta }{3}\frac{v^2}{c^2}$. Standard model extension is a widely used dynamic frame to characterize the Lorentz violation, in which a space-orientation dependence violating background field is regarded as the essential reason for the Lorentz violation effect. Compared with the RMS frame which only indicates the kinematic properties with the coordinate transformation, this dynamic frame provides a more complete and clear description for the Lorentz violation effect.

    ↳ gr-qchep-ph0 citations
19. 19*

    Formation of supermassive primordial black holes by Affleck-Dine mechanism

    Masahiro Kawasaki🇯🇵 · Kai Murai🇯🇵

    We study the supermassive black holes (SMBHs) observed in the galactic centers. Although the origin of SMBHs has not been well understood yet, previous studies suggest that seed black holes (BHs) with masses $10^{4-5}{M}_{\odot }$ exist at a high redshift ($z\sim 10$). We examine whether primordial black holes (PBHs) produced by inhomogeneous baryogenesis can explain those seed black holes. The inhomogeneous baryogenesis is realized in the modified Affleck-Dine mechanism. In this scenario, there is no stringent constraint from CMB $\mu$-distortion in contrast to the scenario where Gaussian fluctuations collapse into PBHs. It is found that the model can account for the origin of the seed BHs of the SMBHs.

    ↳ astro-ph.COhep-phPRD(2019)·36 citations
20. 20*

    Eccentricity Without Measuring Eccentricity: Discriminating Among Stellar Mass Black Hole Binary Formation Channels

    Lisa Randall🇺🇸 · Zhong-Zhi Xianyu🇺🇸

    We show how the observable number of binaries in LISA is affected by eccentricity through its influence on the peak gravitational wave frequency, enhanced binary number density required to produce the LIGO observed rate, and the reduced signal-to-noise ratio for an eccentric event. We also demonstrate how these effects should make it possible to learn about the eccentricity distribution and formation channels by counting the number of binaries as a function of frequency, even with no explicit detection of eccentricity. We also provide a simplified calculation for signal-to-noise ratio of eccentric binaries.

    ↳ astro-ph.HEgr-qchep-phApJ(2021)·29 citations
21. 21*

    Effect of polarisation and choice of event generator on spectra from dark matter annihilations

    Carl Niblaeus🇸🇪 · Jonathan M. Cornell🇺🇸 · Joakim Edsjö🇸🇪

    If indirect detection searches are to be used to discriminate between dark matter particle models, it is crucial to understand the expected energy spectra of secondary particles such as neutrinos, charged antiparticles and gamma-rays emerging from dark matter annihilations in the local Universe. In this work we study the effect that both the choice of event generator and the polarisation of the final state particles can have on these predictions. For a variety of annihilation channels and dark matter masses, we compare yields obtained with Pythia8 and Herwig7 of all of the aforementioned secondary particle species. We investigate how polarised final states can change these results and do an extensive study of how the polarisation can impact the expected flux of neutrinos from dark matter annihilations in the centre of the Sun. We find that differences between the event generators are larger for yields of hadronic end products such as antiprotons, than for leptonic end products. Concerning polarisation, we conversely find the largest differences in the leptonic spectra. The large differences in the leptonic spectra point to the importance of including polarisation effects in searches for neutrinos from dark matter annihilations in the Sun. However, we find that these differences are ultimately somewhat washed out by propagation effects of the neutrinos in the Sun.

    ↳ astro-ph.HEhep-phJCAP(2019)·9 citations
22. 22*

    String Regge trajectory in de Sitter space and implications for inflation

    Toshifumi Noumi🇯🇵 · Toshiaki Takeuchi🇯🇵 · Siyi Zhou🇨🇳

    We study the spectrum of semiclassical rotating strings in de Sitter space and its consistency. Even though a naive extrapolation of the linear Regge trajectory on flat space implies a violation of the Higuchi bound (a unitarity bound on the mass of higher-spin particles in de Sitter space), the curved space effects turn out to modify the trajectory to respect the bound. Interestingly, as a consequence of accelerated expansion, there exists a maximum spin for each Regge trajectory, which is helpful to make the spectrum consistent with the Higuchi bound, but at the same time, it could be an obstruction to stringy UV completion based on an infinite higher-spin tower. By pushing further this observation, we demonstrate that the vacuum energy $V$ inflating the universe has to be bounded by the string scale $M_s$ as $V\lesssim M_s^4$, if UV completion is achieved with the leading Regge trajectory of higher spin states up to the 4D Planck scale. Its application to inflation in the early universe implies an upper bound on the tensor-to-scalar ratio, $r\lesssim 0.01\times (M_s/10^{16}\text{GeV}{)}^4$, which is within the scope of the near future CMB experiments. We also discuss another possibility that UV completion is achieved by multiple Regge trajectories.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2020)·25 citations

* 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.