Thu·May 9, 2019Thursday·May 9, 2019

1. 01*

   Partonic angular momentum in the nucleon's chiral periphery

   Carlos Granados🇺🇸 · Christian Weiss🇺🇸

   We study the nucleon's partonic angular momentum (AM) content at peripheral transverse distances $b=\mathcal{O}(M_{\pi }^{-1})$, where the structure is governed by chiral dynamics. We compute the nucleon form factors of the energy-momentum tensor in chiral effective field theory (ChEFT) and construct the transverse densities of AM at fixed light-front time. In the periphery the spin density is suppressed, and the AM is predominantly orbital. In the first-quantized representation of ChEFT in light-front form, the field-theoretical AM density coincides with the quantum-mechanical orbital AM density of the soft pions in the nucleon's periphery.

   hep-phnucl-thPLB(2019)·14 citations
2. 02*

   The Polarising Fragmentation Function and the Lambda polarisation in e+ e- processes

   Mauro Anselmino🇮🇹 · Raj Kishore🇮🇳 · Asmita Mukherjee🇮🇳

   The surprising polarisation of Lambdas and other hyperons measured in many unpolarised hadronic processes, p N --> Lambda X, has been a long standing challenge for QCD phenomenology. One possible explanation was suggested, related to non perturbative properties of the quark hadronisation process, and encoded in the so-called Polarising Fragmentation Function (PFF). Recent Belle data have shown a non zero Lambda polarisation also in unpolarised e+ e- processes, e+ e- --> Lambda X and e+ e- --> Lambda h X. We consider the single inclusive case and the role of the PFFs. Adopting a simplified kinematics it is shown how they can originate a polarisation P_Lambda different from 0 and give explicit expressions for it in terms of the PFFs. Although the Belle data do not allow yet, in our approach, an extraction of the PFFs, some clear predictions are given, suggesting crucial measurements, and estimates of P_Lambda are computed, in qualitative agreement with the Belle data.

   hep-phPRD(2019)·18 citations
3. 03*

   The relativistic corrections to the fragmentation functions for a heavy quark to $B_c$ and $B_c^{\ast }$

   Deshan Yang🇨🇳 · Wenjie Zhang🇨🇳

   In this paper, we compute the relativistic corrections to the fragmentation functions (FFs) of a heavy quark to $B_c$ and $B_c^{\ast }$ within the framework of non-relativistic QCD (NRQCD) factorization. The non-singlet and singlet DGLAP evolution are also presented.

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

   Direct Higgs-gravity interaction and stability of our Universe

   Vincenzo Branchina🇮🇹 · Eloisa Bentivegna🇮🇹 · Filippo Contino🇮🇹 · Dario Zappalà🇮🇹

   The Higgs effective potential becomes unstable at approximately $10^{11}$ GeV, and if only standard model interactions are considered, the lifetime $\tau$ of the electroweak vacuum turns out to be much larger than the age of the Universe $T_U$. It is well known, however, that $\tau$ is extremely sensitive to the presence of unknown new physics: the latter can enormously lower $\tau$. This poses a serious problem for the stability of our Universe, demanding for a physical mechanism that protects it from a disastrous decay. We have found that there exists a universal stabilizing mechanism that naturally originates from the nonminimal coupling between gravity and the Higgs boson. As this Higgs-gravity interaction necessarily arises from the quantum dynamics of the Higgs field in a gravitational background, this stabilizing mechanism is certainly present. It is not related to any specific model, being rather natural and universal as it comes from fundamental pillars of our physical world: gravity, the Higgs field, the quantum nature of physical laws.

   hep-phgr-qchep-thPRD(2019)·20 citations
5. 05*

   Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars

   Koichi Hamaguchi🇯🇵 · Natsumi Nagata🇯🇵 · Keisuke Yanagi🇯🇵

   Dark matter (DM) particles in the Universe accumulate in neutron stars (NSs) through their interactions with ordinary matter. It has been known that their annihilation inside the NS core causes late-time heating, with which the surface temperature becomes a constant value of $T_s\simeq (2-3)\times 10^3$ K for the NS age $t\gtrsim 10^{6-7}$ years. This conclusion is, however, drawn based on the assumption that the beta equilibrium is maintained in NSs throughout their life, which turns out to be invalid for rotating pulsars. The slowdown in the pulsar rotation drives the NS matter out of beta equilibrium, and the resultant imbalance in chemical potentials induces late-time heating, dubbed as rotochemical heating. This effect can heat a NS up to $T_s\simeq 10^6$ K for $t\simeq 10^{6-7}$ years. In fact, recent observations found several old NSs whose surface temperature is much higher than the prediction of the standard cooling scenario and is consistent with the rotochemical heating. Motivated by these observations, in this letter, we reevaluate the significance of the DM heating in NSs, including the effect of the rotochemical heating. We then show that the signature of DM heating can still be detected in old ordinary pulsars, while it is concealed by the rotochemical heating for old millisecond pulsars. To confirm the evidence for the DM heating, however, it is necessary to improve our knowledge on nucleon pairing gaps as well as to evaluate the initial period of the pulsars accurately. In any cases, a discovery of a very cold NS can give a robust constraint on the DM heating, and thus on DM models. To demonstrate this, as an example, we also discuss the case that the DM is the neutral component of an electroweak multiplet, and show that an observation of a NS with $T_s\lesssim 10^3$ K imposes a stringent constraint on such a DM candidate.

   hep-phastro-ph.HEPLB(2019)·74 citations
6. 06*

   Measuring the heavy neutrino oscillations in rare W boson decays at the Large Hadron Collider

   Gorazd Cvetic🇨🇱 · Arindam Das🇯🇵 · Sebastian Tapia🇺🇸 · Jilberto Zamora-Saa🇨🇱

   Majorana neutrinos in the seesaw model can have sizable mixings through which they can be produced at the Large Hadron Collider (LHC) and show a remarkable Lepton Number Violating (LNV) signature. In this article we study the LNV decay of the W boson via two almost degenerate heavy on-shell Majorana neutrinos $N_j$, into three charged leptons and a light neutrino. We consider the scenario where the heavy neutrino masses are within $1$ GeV $\le M_N\le 10$ GeV. We evaluated the possibility to measure a LNV oscillation process in such a scenario, namely, the modulation of the quantity $d\Gamma /dL$ for the process at the LHC where $W^{\pm }\to {\mu }^{\pm }N\to {\mu }^{\pm }{\tau }^{\pm }{W}^{\mp \ast }$ $\to {\mu }^{\pm }{\tau }^{\pm }{e}^{\mp }{\nu }_e$. $L$ is the distance within the detector between the two vertices of the process. We found out some realistic conditions under which such a modulation could be probed at the LHC.

   hep-phJ.Phys.G(2020)·33 citations
7. 07*

   Dark Matter freezeout in modified cosmological scenarios

   Alexandre Poulin🇨🇦

   We study the effects of modifying the expansions history of the Universe on Dark Matter freezeout. We derived a modified Boltzmann equation for freeze-out for an arbitrary energy density in the early Universe and provide an analytic approach using some approximations. We then look at the required thermally averaged cross sections needed to obtain the correct relic density for the specific case where the energy density consists of radiation plus one extra component which cools faster. We compare our analytic approximation to a numerical solutions. We find that it gives reasonable results for most of the parameter space explored, being at most a factor of order one away from the measured value. We find that if the new contribution to the energy density is comparable to the radiation density, then a much smaller cross section for Dark Matter annihilation is required. This would lead to weak scale Dark Matter being much more difficult to detect and opens up the possibility that much heavier Dark Matter could undergo freezeout without violating perturbative unitarity.

   hep-phPRD(2019)·22 citations
8. 08*

   Constraining Sterile Neutrino Cosmology with Terrestrial Oscillation Experiments

   Jeffrey M. Berryman🇺🇸

   We explore the complementarity between terrestrial neutrino oscillation experiments and astrophysical/cosmological measurements in probing the existence of sterile neutrinos. We find that upcoming accelerator neutrino experiments will not improve on constraints by the time they are operational, but that reactor experiments can already probe parameter space beyond the reach of Planck. We emphasize the tension between cosmological experiments and reactor antineutrino experiments and enumerate several possibilities for resolving this tension.

   hep-phastro-ph.COPRD(2019)·30 citations
9. 09*

   Revisiting the production of ALPs at B-factories

   L. Merlo🇪🇸 · F. Pobbe🇮🇹 · S. Rigolin🇮🇹 · O. Sumensari🇮🇹

   In this paper, the production of Axion-Like Particles (ALPs) at $B$-factories via the process $e^{+}{e}^{-}\to \gamma a$ is revisited. To this purpose, the relevant cross-section is computed via an effective Lagrangian with simultaneous ALP couplings to $b$-quarks and photons. The interplay between resonant and non-resonant contributions is shown to be relevant for experiments operating at $\sqrt{s}=m_{{\rm Y}(nS)}$, with $n=1,2,3$, while the non-resonant one dominates at ${\rm Y}(4S)$. These effects imply that the experimental searches performed at different quarkonia resonances are sensitive to complementary combinations of ALP couplings. To illustrate these results, constraints from existing BaBar and Belle data on ALPs decaying into invisible final states are derived, and the prospects for the Belle-II experiment are discussed.

   hep-phJHEP(2019)·78 citations
10. 10*

    A New Contribution To The Proton Spin Crisis: Non-Zero Boundary Surface Term Due To Confinement in QCD

    Gouranga C Nayak

    The proton spin crisis still remains an unsolved problem in particle physics. It is suggested in the literature that the gauge invariant spin and orbital angular momentum of the quark and the gauge invariant total angular momentum of the gluon contribute to the proton spin. However, in this paper we find a new contribution to the proton spin. This new contribution is due to the boundary surface term in the total angular momentum conservation equation in QCD which is non-zero due to the confinement of the quarks and gluons inside the finite size proton. We derive the non-perturbative formula of this new contribution to the proton spin which can be calculated by using the lattice QCD method.

    hep-phhep-lat3 citations
11. 11*

    Yields of weakly-bound light nuclei as a probe of the statistical hadronization model

    Yiming Cai🇺🇸 · Thomas D. Cohen🇺🇸 · Boris A. Gelman🇺🇸 · Yukari Yamauchi🇺🇸

    The statistical hadronization model is a simple and efficient phenomenological framework in which the relative yields for very high energy heavy ion collisions are essentially determined by a single model parameter---the chemical freeze-out temperature. Recent measurements of yields of hadrons and light nuclei covering over 9 orders of magnitudes from the ALICE collaboration at the LHC were described by the model with remarkable accuracy with a chemical freeze-out temperature of 156.5 $\pm$ 1.5 MeV. A key physical question is whether the freeze-out temperature can be understood, literally, as the temperature at which the various species of an equilibrated gas of hadrons (including resonances) and nuclei chemically freeze out as the model assumes, or whether it successfully parametrizes the yield data for a different reason. The yields of weakly-bound light nuclei---the deuteron and the hypertriton---provide insights into this issue. The analysis indicates that a key assumption underlying the model---that hadrons (and nuclei), just prior to chemical freeze-out temperature, are in thermal equilibrium and are sufficiently dilute as to have particle distributions accurately described statistically by a nearly ideal gas of hadrons and nuclei with masses given by their free space values---appears to be inconsistent with the chemical freeze-out temperature output by the model, at least for these weakly-bound nuclei.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2019)·27 citations
12. 12*

    Low redshift constraints on energy-momentum-powered gravity models

    M. C. F. Faria🇵🇹 · C. J. A. P. Martins🇵🇹 · F. Chiti🇮🇹 · B. S. A. Silva🇵🇹

    There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models, in which the matter side of Einstein's equations is modified by the addition of a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. In this work we treat these models as phenomenological extensions of the standard $\Lambda$CDM, containing both matter and a cosmological constant. We also quantitatively constrain the additional model parameters using low redshift background cosmology data that are specifically from Type Ia supernovas and Hubble parameter measurements. We start by studying specific cases of these models with fixed values of $n,$ which lead to an analytic expression for the Friedmann equation; we discuss both their current constraints and how the models may be further constrained by future observations of Type Ia supernovas for WFIRST complemented by measurements of the redshift drift by the ELT. We then consider and constrain a more extended parameter space, allowing $n$ to be a free parameter and considering scenarios with and without a cosmological constant. These models do not solve the cosmological constant problem per se. Nonetheless these models can phenomenologically lead to a recent accelerating universe without a cosmological constant at the cost of having a preferred matter density of around ${\Omega }_M\sim 0.4$ instead of the usual ${\Omega }_M\sim 0.3$. Finally we also briefly constrain scenarios without a cosmological constant, where the single component has a constant equation of state which needs not be that of matter; we provide an illustrative comparison of this model with a more standard dynamical dark energy model with a constant equation of state.

    ↳ astro-ph.COgr-qchep-phhep-thAstron.Astrophys.(2019)·34 citations
13. 13*

    Reflections On the Anomalous ANITA Events: The Antarctic Subsurface as a Possible Explanation

    Ian M. Shoemaker🇺🇸 · Alexander Kusenko🇯🇵 · Peter Kuipers Munneke🇳🇱 · Andrew Romero-Wolf🇺🇸 · Dustin M. Schroeder🇺🇸 · Martin J. Siegert🇬🇧

    The ANITA balloon experiment was designed to detect radio signals initiated by neutrinos and cosmic ray air showers. These signals are typically discriminated by the polarization and phase inversions of the radio signal. The reflected signal from cosmic rays suffer phase inversion compared to a direct tau neutrino event. In this paper we study sub-surface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by ANITA. We find that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. This hypothesis can be tested with radar surveying of the Antarctic region in the vicinity of the anomalous ANITA events. Future experiments should not use phase inversion as a sole criterion to discriminate between downgoing and upgoing events, unless the subsurface reflection properties are well understood.

    ↳ astro-ph.HEhep-phAnnals Glaciol.(2020)·42 citations
14. 14*

    Scalar dark matter in the radio-frequency band: atomic-spectroscopy search results

    D. Antypas🇩🇪 · O. Tretiak🇩🇪 · A. Garcon🇩🇪 · R. Ozeri🇮🇱 · G. Perez🇮🇱 · D. Budker🇩🇪

    Among the prominent candidates for dark matter are bosonic fields with small scalar couplings to the Standard-Model particles. Several techniques are employed to search for such couplings and the current best constraints are derived from tests of gravity or atomic probes. In experiments employing atoms, observables would arise from expected dark-matter-induced oscillations in the fundamental constants of nature. These studies are primarily sensitive to underlying particle masses below $10^{-14}$ eV. We present a method to search for fast oscillations of fundamental constants using atomic spectroscopy in cesium vapor. We demonstrate sensitivity to scalar interactions of dark matter associated with a particle mass in the range $8\cdot 10^{-11}$ to $4\cdot 10^{-7}$ eV. In this range our experiment yields constraints on such interactions, which within the framework of an astronomical-size dark matter structure, are comparable with, or better than, those provided by experiments probing deviations from the law of gravity.

    ↳ physics.atom-phhep-phPRL(2019)·64 citations
15. 15*

    ABJM quantum spectral curve at twist 1: algorithmic perturbative solution

    R.N. Lee🇷🇺 · A.I. Onishchenko🇷🇺

    We present an algorithmic perturbative solution of ABJM quantum spectral curve at twist 1 in sl(2) sector for arbitrary spin values, which can be applied to, in principle, arbitrary order of perturbation theory. We determined the class of functions -- products of rational functions in spectral parameter with sums of Baxter polynomials and Hurwitz functions -- closed under elementary operations, such as shifts and partial fractions, as well as differentiation. It turns out, that this class of functions is also sufficient for finding solutions of inhomogeneous Baxter equations involved. For the latter purpose we present recursive construction of the dictionary for the solutions of Baxter equations for given inhomogeneous parts. As an application of the proposed method we present the computation of anomalous dimensions of twist 1 operators at six loop order. There is still a room for improvements of the proposed algorithm related to the simplifications of arising sums. The advanced techniques for their reduction to the basis of generalized harmonic sums will be the subject of subsequent paper. We expect this method to be generalizable to higher twists as well as to other theories, such as N=4 SYM.

    ↳ hep-thhep-phmath-phmath.MPJHEP(2019)·12 citations
16. 16*

    Feed-down effect on $\Lambda$ spin polarization

    Xiao-Liang Xia🇨🇳 · Hui Li🇨🇳 · Xu-Guang Huang🇨🇳 · Huan Zhong Huang🇺🇸

    We develop a theoretical framework to study the feed-down effect of higher-lying strange baryons on the spin polarization of the $\Lambda$ hyperon. In this framework, we consider two-body decays through strong, electromagnetic, and weak processes and derive general formulas for the angular distribution and spin polarization of the daughter particle by adopting the helicity formalism. Using the realistic experimental data as input, we explore the feed-down contribution to the global and the local $\Lambda$ polarizations and find that such a contribution suppresses the primordial $\Lambda$ polarization, which is not strong enough to resolve the discrepancy between the current theoretical and the experimental results on the azimuthal-angle dependence of $\Lambda$ polarization. Our paper may also be useful for the measurement of spin polarization of baryons heavier than $\Lambda$ (e.g., ${\Xi }^{-}$) in future experiments.

    ↳ nucl-thhep-phPRC(2019)·91 citations
17. 17*

    Polarization transfer in hyperon decays and its effect in relativistic nuclear collisions

    F. Becattini (University of Florence)🇮🇹 · Gaoqing Cao (Sun Yat-Sen University)🇨🇳 · Enrico Speranza (University of Frankfurt)🇩🇪

    We calculate the contribution to the polarization of $\Lambda$ hyperons in relativistic nuclear collisions at high energy from the decays of ${\Sigma }^{\ast }(1385)$ and ${\Sigma }^0$, which are the predominant sources of $\Lambda$ production besides the primary component, as a function of the $\Lambda$ momentum. Particularly, we estimate the longitudinal component of the mean spin vector as a function of the azimuthal angle in the transverse plane, assuming that primary ${\Sigma }^{\ast }$ and ${\Sigma }^0$ polarization follow the predictions of local thermodynamic equilibrium in a relativistic fluid. Provided that the rapidity dependence around midrapidity of polarization is negligible, we find that this component of the overall spin vector has a very similar pattern to the primary one. Therefore, we conclude that the secondary decays cannot account for the discrepancy in sign between experimental data and hydrodynamic model predictions of the longitudinal polarization of $\Lambda$ hyperons recently measured by the STAR experiment at RHIC.

    ↳ nucl-thhep-phEPJC(2019)·103 citations
18. 18*

    Perturbations in higher derivative gravity beyond maximally symmetric spacetimes

    K. Sravan Kumar🇳🇱 · Shubham Maheshwari🇳🇱 · Anupam Mazumdar🇳🇱

    We study (covariant) scalar-vector-tensor (SVT) perturbations of infinite derivative gravity (IDG), at the quadratic level of the action, around conformally-flat, covariantly constant curvature backgrounds which are not maximally symmetric spacetimes (MSS). This extends a previous analysis of perturbations done around MSS, which were shown to be ghost-free. We motivate our choice of backgrounds which arise as solutions of IDG in the UV, avoiding big bang and black hole singularities. Contrary to MSS, in this paper we show that, generically, all SVT modes are coupled to each other at the quadratic level of the action. We consider simple examples of the full IDG action, and illustrate this mixing and also a case where the action can be diagonalized and ghost-free solutions constructed. Our study is widely applicable for both non-singular cosmology and black hole physics where backgrounds depart from MSS. In appendices, we provide SVT perturbations around conformally-flat and arbitrary backgrounds which can serve as a compendium of useful results when studying SVT perturbations of various higher derivative gravity models.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2019)·18 citations
19. 19*

    Forecast constraints on $f(T)$ gravity with gravitational waves from compact binary coalescences

    Rafael C. Nunes🇧🇷 · Marcio E. S. Alves🇧🇷 · Jose C. N. de Araujo🇧🇷

    The direct detection of gravitational waves (GWs) opened a new chapter in the modern cosmology to probe possible deviations from the general relativity (GR) theory. In the present work, we investigate for the first time the modified GW form propagation from the inspiraling of compact binary systems within the context of $f(T)$ gravity in order to obtain new forecasts/constraints on the free parameter of the theory. First, we show that the modified waveform differs from the GR waveform essentially due to induced corrections on the GWs amplitude. Then, we discuss the forecasts on the $f(T)$ gravity assuming simulated sources of GWs as black hole binaries, neutron star binaries and black hole - neutron star binary systems, which emit GWs in the frequency band of the Advanced LIGO (aLIGO) interferometer and of the third generation Einstein Telescope (ET). We show that GWs sources detected within the aLIGO sensitivity can return estimates of the same order of magnitude of the current cosmological observations. On the other hand, detection within the ET sensitivity can improve by up to 2 orders of magnitude the current bound on the $f(T)$ gravity. Therefore, the statistical accuracy that can be achieved by future ground based GW observations, mainly with the ET detector (and planed detectors with a similar sensitivity), can allow strong bounds on the free parameter of the theory, and can be decisive to test the theory of gravitation.

    ↳ gr-qcastro-ph.COhep-phPRD(2019)·53 citations
20. 20*

    Critical end points in (2+1)-flavor QCD with imaginary chemical potential

    Jishnu Goswami🇩🇪 · Frithjof Karsch🇩🇪 · Anirban Lahiri🇩🇪 · Marius Neumann🇩🇪 · Christian Schmidt🇩🇪

    We present here the results from an ongoing determination of the critical quark mass in simulations of (2+1)-flavor QCD with an imaginary chemical potential. Studies with unimproved actions found the existence of a critical quark mass value at which the crossover transition ends on a second order phase transition and becomes first order for smaller values of the quark mass for the case of both vanishing and imaginary chemical potential. We use the Highly Improved Staggered Quark (HISQ) action and perform calculations in the Roberge-Weiss (RW) plane, where the value of the critical mass is expected to be largest. The lowest quark mass value used in our simulation corresponds to the pion mass $m_{\pi }$, down to $40$ MeV. Contrary to calculations performed with unimproved actions we find no evidence for the occurrence of first order transitions at the smallest quark mass values explored so far. Moreover we also show that the chiral observables are sensitive to the RW transition. Our results also indicate that the RW transition and chiral transition could coincide in the chiral limit.

    ↳ hep-lathep-phnucl-thPoS(2019)·10 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.