Tue·Oct 30, 2018Tuesday·October 30, 2018

1. 01*

   Axion Stars

   Eric Braaten · Hong Zhang

   The particle that makes up the dark matter of the universe could be an axion or axion-like particle. A collection of axions can condense into a bound Bose-Einstein condensate called an axion star. It is possible that a significant fraction of the axion dark matter is in the form of axion stars. This would make some efforts to identify the axion as the dark matter particle more challenging, but it would also open up new possibilities. We summarize the basic properties of isolated axion stars, which can be gravitationally bound or bound by self-interactions. Axions are naturally described by a relativistic field theory with a real scalar field, but low-energy axions can be described more simply by a classical nonrelativistic effective field theory with a complex scalar field.

   hep-phSymmetry(2019)·56 citations
2. 02*

   Unambiguous Extraction of the Electromagnetic Form Factors for Spin-1 Particles on the Light-Front

   J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional - LFTC, Universidade Cruzeiro do Sul, Brazil)🇧🇷

   The electromagnetic form factors of a composite vector particle within the light-front formulation of the Mandelstam formula is investigated. In order to extract the form factors from the matrix elements of the plus component of the current in the Drell-Yan frame, where the momentum transfer is chosen such that $q^{+}=q^0+q^3=0$, one has in principle the freedom to choose between different linear combinations of matrix elements of the current operator. The different prescriptions to calculate the electromagnetic form factors, $G_0,G_1$ and $G_2$, i.e., charge form factor, magnetic and quadrupole respectively. If the covariance is respected, all prescriptions give the same results, misfortune, is not the situation, the light-front approach produce different results, which depend of the prescriptions as utilized to extract the electromagnetic form factors in the case of the spin-1 particles. The main differences of the prescriptions appear because of the light-front matrix elements of the electromagnetic current are contaminated by the zero-modes contributions to the same with the plus component of the matrix elements of the electromagnetic current. However, the Inna Grach prescription is immune to the zero-modes contributions to the electromagnetic current, then the electromagnetic form factors extracted with that prescriptions do not have zero-modes contribution and give the same result compared with the instant form quantum field theory. Another's prescriptions with the light-front approach are contaminated by the zero-modes contributions to the matrix elements of the electromagnetic current with the plus component of the current.

   hep-phPLB(2019)·11 citations
3. 03*

   Neural Network-Based Approach to Phase Space Integration

   Matthew D. Klimek🇺🇸 · Maxim Perelstein🇺🇸

   Monte Carlo methods are widely used in particle physics to integrate and sample probability distributions (differential cross sections or decay rates) on multi-dimensional phase spaces. We present a Neural Network (NN) algorithm optimized to perform this task. The algorithm has been applied to several examples of direct relevance for particle physics, including situations with non-trivial features such as sharp resonances and soft/collinear enhancements. Excellent performance has been demonstrated in all examples, with the properly trained NN achieving unweighting efficiencies of between 30% and 75%. In contrast to traditional Monte Carlo algorithms such as VEGAS, the NN-based approach does not require that the phase space coordinates be aligned with resonant or other features in the cross section.

   hep-phhep-exphysics.comp-phstat.MLSciPost Phys.(2020)·93 citations
4. 04*

   Odderon, HEGS model and LHC data

   O.V. Selyugin🇷🇺 · J.R. Cudell🇧🇪

   We show that the impact of the maximal odderon amplitude at t=0 and centre-of-momentum energy 13 TeV is small. We obtain a value of rho(t=0) at 13 TeV of the order of 0.12. The real part of the odderon amplitude grows like log(s/s0) at high energies, and is calculated from the analytic properties of the amplitude. In the framework of the HEGS model, taking the same intercept for the odderon and the pomeron leads to a good fit of the new LHC data at 13 TeV. We also show that the main effect of the odderon can be seen in the region of the diffraction minimum of the differential elastic cross section. The form and energy dependence of the odderon amplitude determined in the HEGS model reproduce the characteristics of the diffraction minimum at 7, 8 and 13 TeV.

   hep-phhep-exActa Phys.Polon.Supp.(2019)·18 citations
5. 05*

   On the Minimal Flavor Violating Leptoquark Explanation of the $R_{D^{(\ast )}}$ Anomaly

   Saurabh Bansal🇺🇸 · Rodolfo M. Capdevilla🇺🇸 · Christopher Kolda🇺🇸

   There has been persistent disagreement between the Standard Model (SM) prediction and experimental measurements of $R_{D^{(\ast )}}=\mathcal{B}(\bar{B}\to D^{(\ast )}\tau {\bar{\nu }}_{\tau })/\mathcal{B}(\bar{B}\to D^{(\ast )}l{\bar{\nu }}_l)$ $(l=e,\mu )$. This anomaly may be addressed by introducing interactions beyond the Standard Model involving new states, such as leptoquarks. Since the processes involved are quark flavor changing, any new states would need to couple to at least two different generations of quarks, requiring a non-trivial flavor structure in the quark sector while avoiding stringent constraints from flavor-changing neutral current processes. In this work, we look at scalar leptoquarks as a possible solution for the $R_{D^{(\ast )}}$ anomaly under the assumption of $minimalflavorviolation$ (MFV). We investigate all possible representations for the leptoquarks under the SM quark flavor symmetry group, consistent with asymptotic freedom. We consider constraints on their parameter space from self-consistency of the MFV scenario, perturbativity, the FCNC decay $b\to s\bar{\nu }\nu$ and precision electroweak observables. We find that none of the scalar leptoquarks can explain the $R_{D^{(\ast )}}$ anomaly while simultaneously avoiding all constraints within this scenario. Thus scalar leptoquarks with MFV-generated quark couplings do not work as a solution to the $R_{D^{(\ast )}}$ anomaly.

   hep-phPRD(2019)·34 citations
6. 06*

   Features of $\omega$ photoproduction off proton target at backward angles : Role of nucleon Reggeon in $u$-channel with parton contributions

   Byung-Geel Yu🇰🇷 · Kook-Jin Kong🇰🇷

   Backward photoproduction of $\omega$ off a proton target is investigated in a Reggeized model where the $u$-channel nucleon Reggeon is constructed from the nucleon Born terms in a gauge invariant way. The $t$-channel meson exchanges are considered as a background. While the $N_{\alpha }$ trajectory of the nucleon Reggeon reproduces the overall shape of NINA data measured at the Daresbury Laboratory in the range of $u$-channel momentum transfer squared $-1.7<u<0.02$ GeV${}^2$ and energies at $E_{\gamma }=2.8$, 3.5 and 4.7 GeV, a possibility of parton contributions is searched for through the nucleon isoscalar form factor which is parameterized in terms of parton distributions at the $\omega NN$ vertex. Detailed analysis is presented for NINA data to understand the reaction mechanism that could fill up the deep dip from the nucleon Reggeon at momentum squared $u=-0.15$ GeV${}^2$. The angle dependence of differential cross sections at the NINA energies above are reproduced in the overall range of $u$ including the CLAS data at forward angles in addition. The energy dependence of the differential cross section is investigated based on the NINA data and the recent LEPS data. A feature of the present approach that implicates parton contributions via nucleon form factor is illustrated in the total and differential cross sections provided by GRAAL and CB-ELSA Collaborations.

   hep-phnucl-thPRD(2019)·7 citations
7. 07*

   Anomalous triple gauge boson couplings in $ZZ$ production at the LHC and the role of $Z$ boson polarizations

   Rafiqul Rahaman🇮🇳 · Ritesh K. Singh🇮🇳

   We study anomalous couplings among neutral gauge bosons in $ZZ$ production at the LHC for $\sqrt{s}=13$ TeV in $4$-lepton final state. We use the cross section and polarization asymmetries of the $Z$ boson to estimate simultaneous limits on anomalous coupling using Markov-Chain--Monte-Carlo (MCMC) method for luminosities $35.9$ fb${}^{-1}$, $150$ fb${}^{-1}$, $300$ fb${}^{-1}$ and $1000$ fb${}^{-1}$. The $CP$-even polarization asymmetry $A_{x^2-y^2}$ is sensitive mainly to the $CP$-odd couplings $f_4^{Z/\gamma }$ (quadratically) providing a probe to identify $CP$-odd nature of interaction at the LHC. We find that the polarization asymmetries significantly improve the estimation of anomalous couplings should a deviation from the Standard Model (SM) be observed.

   hep-phhep-exNPB(2019)·44 citations
8. 08*

   Constraining minimal Type-III Seesaw Model from naturalness, Lepton Flavor Violation and Electroweak Vacuum stability

   Srubabati Goswami🇮🇳 · Vishnudath K. N.🇮🇳 · Najimuddin Khan🇮🇳

   We study the minimal type-III seesaw model in which we extend the SM by adding two $SU(2{)}_L$ triplet fermions with zero hypercharge to explain the origin of the non-zero neutrino masses. We show that the naturalness conditions and the limits from lepton flavor violating decays provide very stringent bounds on the model parameters along with the constraints from the stability/metastability of the electroweak vacuum. We perform a detailed analysis of the model parameter space including all the constraints for both normal as well as inverted hierarchies of the light neutrino masses. We find that most of the region that are allowed by lepton flavor violating decays and naturalness fall in the stable/metastable region depending on the values of the standard model parameters.

   hep-phPRD(2019)·26 citations
9. 09*

   Proton Spin in Deep Inelastic Scattering

   B. Povh🇩🇪 · M. Rosina🇸🇮

   So far the analyses of the polarized structure functions of the proton and neutron have been limited to the evaluation of their integrals and comparing them to the prediction of the static quark model of the nucleon. We extended our analysis to the x dependence of the polarized structure functions and observe: the measured structure function excellently agrees with the prediction of the static quark model for Bjorken $x>0.2$ and drops rapidly for $x<0.2$. It is suggested that for Bjorken $x>0.2$ electrons get scattered on the undamaged constituent quarks (alias valence quarks) denoted as quasi-elastic scattering on the constituent quarks and for $x<0.2$ the constituent quarks fragment. In the fragmentation strong interaction is involved which does not preserve the polarization.

   hep-phActa Phys.Polon.Supp.(2019)·0 citations
10. 10*

    Quasinormal modes and dispersion relations for quarkonium in a plasma

    Nelson R. F. Braga🇧🇷 · Luiz F. Ferreira🇧🇷

    Recent investigations show that the thermal spectral function of heavy $b\bar{b}$ and $c\bar{c}$ vector mesons can be described using holography. These studies consider a bottom up model that captures the heavy flavour spectroscopy of masses and decay constants in the vacuum and is consistently extended to finite temperature. The corresponding spectral functions provide a picture of the dissociation process in terms of the decrease of the quasi-state peaks with temperature. Another related tool that provides important information about the thermal behaviour is the analysis of the quasinormal modes. They are field solutions in a curved background assumed to represent, in gauge/gravity duality, quasi-particle states in a thermal medium. The associated complex frequencies are related to the thermal mass and width. We present here the calculation of quasinormal modes for charmonium and bottomonium using the holographic approach. The temperature dependence of mass and thermal width are investigated. Solutions corresponding to heavy mesons moving into the plasma are also studied. They provide the dependence of the real and imaginary parts of the frequency with the quasi-particle momenta, the so called dispersion relations.

    hep-phhep-thJHEP(2019)·13 citations
11. 11*

    Semileptonic $D_{(s)}$-meson decays in the light of recent data

    Nakul R. Soni🇮🇳 · Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Jignesh N. Pandya🇮🇳 · Pietro Santorelli🇮🇹 · Chien-Thang Tran🇮🇹

    Inspired by recent improved measurements of charm semileptonic decays at BESIII, we study a large set of $D(D_s)$-meson semileptonic decays where the hadron in the final state is one of $D^0$, $\rho$, $\omega$, ${\eta }^{(\prime )}$ in the case of $D^{+}$ decays, and $D^0$, $\varphi$, $K^0$, $K^{\ast }(892{)}^0$, ${\eta }^{(\prime )}$ in the case of $D_s^{+}$ decays. The required hadronic form factors are computed in the full kinematical range of momentum transfer by employing the covariant confined quark model developed by us. A detailed comparison of the form factors with those from other approaches is provided. We calculate the decay branching fractions and their ratios, which show good agreement with available experimental data. We also give predictions for the forward-backward asymmetry and the longitudinal and transverse polarizations of the charged lepton in the final state.

    hep-phPRD(2018)·75 citations
12. 12*

    On the robustness of IceCube's bound on sterile neutrinos in the presence of non-standard interactions

    Arman Esmaili🇧🇷 · Hiroshi Nunokawa🇧🇷

    The mixing parameters of sterile neutrino(s) preferred by the MiniBooNE and LNSD experiments are in strong tension with the exclusion limit from the IceCube experiment. Recently it has been claimed that by considering the non-standard neutrino interactions (NSI) in addition to the sterile neutrino, the IceCube's limit can be relaxed and the tension can be reconciled; a baroque scenario as it has been called. We will show that this claim is just an artifact originating from the energy cuts of the chosen datasets. Contrary to the claim, by turning on the NSI and fixing the NSI parameters to the proposed values, not only the IceCube's limit on sterile neutrino cannot be alleviated, but in fact the tension will be aggravated. The reconciliation, more appropriately, can be called surreal.

    hep-phEPJC(2019)·23 citations
13. 13*

    Chiral Perturbation Theory with an Isosinglet Scalar

    Martin Hansen🇮🇹 · Kasper Langæble🇩🇰 · Francesco Sannino🇩🇰

    We present an extension of chiral perturbation theory that explicitly includes an isosinglet scalar in the Lagrangian. The dynamical effects from the scalar state is of phenomenological relevance in theories where the mass of the isosinglet scalar is comparable to the mass of the pseudo-Goldstone bosons. This near-degeneracy of states is for example observed in certain near-conformal BSM models. From the Lagrangian we calculate the one-loop radiative corrections to the pion mass, the pion decay constant, and the scalar mass. We then proceed and use the results to fit numerical lattice data for an SU(3) gauge theory with $N_f=8$ light flavours in the fundamental representation.

    hep-phhep-latPoS(2019)·2 citations
14. 14*

    Towards a new approximation for pair-production and associated-production of the Higgs boson

    Xiaofeng Xu🇨🇳 · Li Lin Yang🇨🇳

    We propose that loop integrals with internal heavy particles can be evaluated by expanding in the limit of small external masses. This provides a systematically improvable approximation to the integrals in the entire phase space, and works particularly well for the high energy tails of kinematic distributions (where the usual $1/M$ expansions cease to be valid). We demonstrate our method using Higgs boson pair production as an example. We find that at both one-loop and two-loop, our method provides good approximations to the integrals appearing in the scattering amplitudes. Comparing to existing expansion methods, our method are not restricted to a special phase space region. Combining our efficient method to compute the two-loop amplitude with an infrared subtraction method for the real emission corrections, we expect to have a fast and reliable tool to calculate the differential cross sections for Higgs boson pair production. This will be useful for phenomenological studies and for the extraction of the Higgs self-coupling from future experimental data. Our method can also be applied to other processes, such as the associated production of the Higgs boson with a jet or a $Z$ boson.

    hep-phJHEP(2019)·47 citations
15. 15*

    Impact of the top quark cross section data on parton distribution functions

    Majid Azizi🇮🇷 · Ali Khorramian🇮🇷 · Hamed Abdolmaleki🇮🇷 · Saeid Paktinat Mehdiabadi🇮🇷

    Recent measurements of top quark pair production cross section, which is performed at the LHC and the Tevatron collider, are studied using Hessian profiling technique to obtain their impact on the parton distribution functions (PDFs). The top quark production data covers different center-of-mass energies $\sqrt{s}$= 1.96, 5.02, 7, 8 and 13 TeV in either $pp$ or $p\bar{p}$ collisions. It is explained how the Hessian profiling method may be used to assess the impact of these new data on PDFs and consequently on their predictions. In this research, the impact of recent measurements of top quark pair cross sections on different CT14, MMHT2014, and NNPDF3.0 PDF sets is investigated. The analysis results show that the recent top quark production at the LHC and Tevatron data provide significant constraints in particular on the central value, relative uncertainties or both for the $s$-quark distribution and the gluon PDFs in both of CT14, MMHT2014 PDF sets and are insensitive to valence quark PDFs. A small constraint on the $\bar{u}$- sea quark distribution for CT14 PDF is also observed. There is no impact on the NNPDF3.0 PDF set in presence of these data.

    hep-phInt.J.Mod.Phys.A(2018)·5 citations
16. 16*

    Indirect Probe of Electroweak-Interacting Particles with Mono-Lepton Signatures at Hadron Colliders

    Shigeki Matsumoto🇯🇵 · Satoshi Shirai🇯🇵 · Michihisa Takeuchi🇯🇵

    Electroweak-interacting massive particles (EWIMPs) exist in a broad class of new physics models beyond the Standard Model. Searching for such particles is one of most primary goal at the LHC and future colliders. The EWIMP generally affects the LHC signatures through quantum corrections even without direct productions. By measuring the Standard Model processes precisely, we can indirectly probe the EWIMPs. In this paper, we study the current constraint and future prospect of the EWIMPs by using the precision measurements of mono-lepton production from the charged Drell-Yan processes at hadron colliders. We found the mono-lepton signature can be a better probe than dilepton signature from the neutral Drell-Yan processes.

    hep-phhep-exJHEP(2019)·17 citations
17. 17*

    The exact discontinuity of a partial wave along the left-hand cut and the exact $N/D$ method in non-relativistic scattering

    J. A. Oller🇪🇸 · D. R. Entem🇪🇸

    We first deduce the analytical continuation in the complex planes of the initial and final three-momenta of the Lippmann-Schwinger equation in coupled or uncoupled partial-wave amplitudes. This result allows us to deduce a master equation whose solution is the exact discontinuity of the on-shell partial-wave amplitudes along the left-hand cut. This equation is always a linear non-singular integral equation whose solution is fixed exclusively by the knowledge of the potential, applicable to either regular or singular potentials. The capability of calculating exactly this discontinuity allows one to settle the exact $N/D$ method in two-body non-relativistic scattering for coupled and uncoupled waves. We exemplify this new advance in scattering theory by explicitly checking the agreement between the Lippmann-Schwinger equation with the corresponding solutions of the exact $N/D$ method for some examples that involve regular and singular potentials, either attractive or repulsive.

    hep-phcond-mat.quant-gashep-thnucl-th+1Annals Phys.(2019)·32 citations
18. 18*

    Automated Solution of First Order Factorizable Systems of Differential Equations in One Variable

    J. Ablinger🇦🇹 · J. Blümlein🇩🇪 · P. Marquard🇩🇪 · N. Rana🇩🇪 · C. Schneider🇦🇹

    We present an algorithm which allows to solve analytically linear systems of differential equations which factorize to first order. The solution is given in terms of iterated integrals over an alphabet where its structure is implied by the coefficient matrix of the differential equations. These systems appear in a large variety of higher order calculations in perturbative Quantum Field Theories. We apply this method to calculate the master integrals of the three--loop massive form factors for different currents, as an illustration, and present the results for the vector form factors in detail. Here the solution space emerging is given by the cyclotomic harmonic polylogarithms and their associated special constants. No special basis representation of the master integrals is needed. The algorithm can be applied as well to more general cases factorizing at first order, which are based on more general alphabets, iterated integrals and associated constants.

    hep-phhep-thmath-phmath.MPNPB(2019)·94 citations
19. 19*

    Etaprime and Eta Mesons with Connection to Anomalous Glue

    Steven D. Bass🇵🇱 · Pawel Moskal🇵🇱

    We review the present understanding of etaprime and eta meson physics and these mesons as a probe of gluon dynamics in low-energy QCD. Recent highlights include the production mechanism of eta and etaprime mesons in proton-nucleon collisions from threshold to high-energy, the etaprime effective mass shift in the nuclear medium, searches for possible eta and etaprime bound states in nuclei as well as precision measurements of eta decays as a probe of light-quark masses. We discuss recent experimental data, theoretical interpretation of the different measurements and the open questions and challenges for future investigation.

    hep-phhep-exnucl-exnucl-thRMP(2019)·100 citations
20. 20*

    Electric dipole moment constraints on CP-violating heavy-quark Yukawas at next-to-leading order

    Joachim Brod🇺🇸 · Emmanuel Stamou🇺🇸

    Electric dipole moments are sensitive probes of new phases in the Higgs Yukawa couplings. We calculate the complete two-loop QCD anomalous dimension matrix for the mixing of CP-odd scalar and tensor operators and apply our results for a phenomenological study of CP violation in the bottom and charm Yukawa couplings. We find large shifts of the induced Wilson coefficients at next-to-leading-logarithmic order. Using the experimental bound on the electric dipole moment of the neutron, we update the constraints on CP-violating phases in the bottom and charm quark Yukawas.

    hep-phJHEP(2021)·47 citations
21. 21*

    Gravitational Waves from First-Order Phase Transitions: LIGO as a Window to Unexplored Seesaw Scales

    Vedran Brdar🇩🇪 · Alexander J. Helmboldt🇩🇪 · Jisuke Kubo🇩🇪

    Within a recently proposed classically conformal model, in which the generation of neutrino masses is linked to spontaneous scale symmetry breaking, we investigate the associated phase transition and find it to be of strong first order with a substantial amount of supercooling. Carefully taking into account the vacuum energy of the metastable minimum, we demonstrate that a significant fraction of the model's parameter space can be excluded simply because the phase transition cannot complete. We argue this to be a powerful consistency check applicable to general theories based on classical scale invariance. Finally, we show that all remaining parameter points predict a sizable gravitational wave signal, so that the model can be fully tested by future gravitational wave observatories. In particular, most of the parameter space can already be probed by the upcoming LIGO science run starting in early 2019.

    hep-phastro-ph.COgr-qcJCAP(2019)·137 citations
22. 22*

    Remarks on the uncertainty relations

    K. Urbanowski🇵🇱

    We analyze general uncertainty relations and we show that there can exist such pairs of non--commuting observables $A$ and $B$ and such vectors that the lower bound for the product of standard deviations $\Delta A$ and $\Delta B$ calculated for these vectors is zero: $\Delta A\cdot \Delta B\ge 0$. We show also that for some pairs of non--commuting observables the sets of vectors for which $\Delta A\cdot \Delta B\ge 0$ can be complete (total). The Heisenberg, $\Delta t\cdot \Delta E\ge \hslash /2$, and Mandelstam--Tamm (MT), ${\tau }_A\cdot \Delta E\ge \hslash /2$, time--energy uncertainty relations (${\tau }_A$ is the characteristic time for the observable $A$) are analyzed too. We show that the interpretation ${\tau }_A=\infty$ for eigenvectors of a Hamiltonian $H$ does not follow from the rigorous analysis of MT relation. We show also that contrary to the position--momentum uncertainty relation, the validity of the MT relation is limited: It does not hold on complete sets of eigenvectors of $A$ and $H$.

    ↳ quant-phgr-qchep-phphysics.pop-phMod.Phys.Lett.A(2020)·6 citations
23. 23*

    Dark energy versus modified gravity: Impacts on measuring neutrino mass

    Ming-Ming Zhao🇨🇳 · Rui-Yun Guo🇨🇳 · Dong-Ze He🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    In this paper, we make a comparison for the impacts of smooth dynamical dark energy, modified gravity, and interacting dark energy on the cosmological constraints on the total mass of active neutrinos. For definiteness, we consider the $\Lambda$CDM model, the $w$CDM model, the $f(R)$ model, and two typical interacting vacuum energy models, i.e., the I$\Lambda$CDM1 model with $Q=\beta H{\rho }_{\mathrm{c}}$ and the I$\Lambda$CDM2 model with $Q=\beta H{\rho }_{\Lambda }$. In the cosmological fits, we use the Planck 2015 temperature and polarization data, in combination with other low-redshift observations including the baryon acoustic oscillations, the type Ia supernovae, the Hubble constant measurement, and the large-scale structure observations, such as the weak lensing as well as the redshift-space distortion. Besides, the Planck lensing measurement is also employed in this work. We find that, the $w$CDM model favors a higher upper limit on the neutrino mass compared to the $\Lambda$CDM model, while the upper limit in the $f(R)$ model is similar with that of $\Lambda$CDM model. For the interacting vacuum energy models, the I$\Lambda$CDM1 model favors a higher upper limit on neutrino mass, while the I$\Lambda$CDM2 model favors an identical neutrino mass with the case of $\Lambda$CDM.

    ↳ astro-ph.COgr-qchep-phSCPMA(2020)·25 citations
24. 24*

    Viscous Self Interacting Dark Matter Cosmology For Small Redshift

    Abhishek Atreya🇮🇳 · Jitesh R. Bhatt🇮🇳 · Arvind Kumar Mishra🇮🇳

    The viscosity of dark matter in cosmological models may cause an accelerated expansion and when this effect is sufficiently large, it can explain the dark energy. In this work, attributing the origin of viscosity to self-interaction of dark matter, we study the viscous cosmology at small redshift $(0\le z\le 2.5)$. Assuming the cluster scale to be virialized and by modeling a power law behavior of velocity gradients, we calculate the Hubble expansion rate, $H(z)$ and the deceleration parameter, $q(z)$. We then perform a ${\chi }^2$ analysis to estimate the best fit model parameters. By using the best fit values, we explain the cosmic chronometer and type Ia supernova data. We conclude that if the dissipative effects become prominent only at the late time of cosmic evolution and are smaller at higher redshift, we can explain the observational data without requiring any dark energy component. Our analysis is independent of any specific model of self interacting dark matter.

    ↳ astro-ph.COhep-phJCAP(2019)·10 citations
25. 25*

    Massive Scattering Amplitudes in Six Dimensions

    Rishabh Jha🇮🇳 · Chethan Krishnan🇮🇳 · K.V. Pavan Kumar🇮🇳

    We show that a natural spinor-helicity formalism that can describe massive scattering amplitudes exists in $D=6$ dimensions. This is arranged by having helicity spinors carry an index in the Dirac spinor {\bf 4} of the massive little group, $SO(5)\sim Sp(4)$. In the high energy limit, two separate kinds of massless helicity spinors emerge as required for consistency with arXiv:0902.0981, with indices in the two $SU(2)$'s of the massless little group $SO(4)$. The tensors of $4$ lead to particles with arbitrary spin, and using these and demanding consistent factorization, we can fix $3-$ and $4-$point tree amplitudes of arbitrary masses and spins: we provide examples. We discuss the high energy limit of scattering amplitudes and the Higgs mechanism in this language, and make some preliminary observations about massive BCFW recursion.

    ↳ hep-thhep-phJHEP(2019)·8 citations
26. 26*

    Magnetism in the Early Universe

    Tina Kahniashvili🇺🇸 · Axel Brandenburg🇸🇪 · Arthur Kosowsky🇺🇸 · Sayan Mandal🇺🇸 · Alberto Roper Pol🇺🇸

    Blazar observations point toward the possible presence of magnetic fields over intergalactic scales of the order of up to $\sim 1$Mpc, with strengths of at least $\sim 10^{-16}$G. Understanding the origin of these large-scale magnetic fields is a challenge for modern astrophysics. Here we discuss the cosmological scenario, focussing on the following questions: (i) How and when was this magnetic field generated? (ii) How does it evolve during the expansion of the universe? (iii) Are the amplitude and statistical properties of this field such that they can explain the strengths and correlation lengths of observed magnetic fields? We also discuss the possibility of observing primordial turbulence through direct detection of stochastic gravitational waves in the mHz range accessible to LISA.

    ↳ astro-ph.COgr-qchep-phIAU Symp.A(2020)·6 citations
27. 27*

    Inferring Cosmic String Tension through the Neural Network Prediction of String Locations in CMB Maps

    Razvan Ciuca🇨🇦 · Oscar F. Hernández🇨🇦

    In previous work, we constructed a convolutional neural network used to estimate the location of cosmic strings in simulated cosmic microwave background temperature anisotropy maps. We derived a connection between the estimates of cosmic string locations by this neural network and the posterior probability distribution of the cosmic string tension $G\mu$. Here, we significantly improve the calculation of the posterior distribution of the string tension $G\mu$. We also improve our previous plain convolutional neural network by using residual networks. We apply our new neural network and posterior calculation method to maps from the same simulation used in our previous work and quantify the improvement.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2019)·8 citations
28. 28*

    What can we know about hypernuclei via analysis of bremsstrahlung photons?

    Xin Liu (1 and 2)🇨🇳 · Sergei P. Maydanyuk (2 and 3)🇨🇳 · Peng-Ming Zhang (2)🇨🇳 · Ling Liu (1) ((1) College of Physical Science and Technology, Shenyang Normal University, Shenyang, 110034, China, (2) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China, (3) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev, 03680, Ukraine)🇨🇳

    We investigate possibility of emission of the bremsstrahlung photons in nuclear reactions with hypernuclei for the first time. A new model of the bremsstrahlung emission which accompanies interactions between $\alpha$ particles and hypernuclei is constructed, where a new formalism for the magnetic momenta of nucleons and hyperon inside hypernucleus is added. For first calculations, we choose $\alpha$ decay of the normal nucleus ${}^{210}\mathrm{Po}$ and the hypernucleus ${}_{\Lambda }^{211}\mathrm{Po}$. We find that (1) emission for the hypernucleus ${}_{\Lambda }^{211}\mathrm{Po}$ is larger than for normal nucleus ${}^{210}\mathrm{Po}$, (2) difference between these spectra is small. We propose a way how to find hypernuclei, where role of hyperon is the most essential in emission of bremsstrahlung photons during $\alpha$ decay. As demonstration of such a property, we show that the spectra for the hypernuclei ${}_{\Lambda }^{107}\mathrm{Te}$ and ${}_{\Lambda }^{109}\mathrm{Te}$ are essentially larger than the spectra for the normal nuclei ${}^{106}\mathrm{Te}$ and ${}^{108}\mathrm{Te}$. Such a difference is explained by additional contribution of emission to the full bremsstrahlung, which is formed by magnetic moment of hyperon inside hypernucleus. The bremsstrahlung emission formed by such a mechanism, is of the magnetic type. A new formula for fast estimations of bremsstrahlung spectra for even-even hypernuclei is proposed, where role of magnetic moment of hyperon of hypernucleus in formation of the bremsstrahlung emission is shown explicitly. Such an analysis opens possibility of new experimental study of properties of hypernuclei via bremsstrahlung study.

    ↳ nucl-thhep-phnucl-ex5 citations
29. 29*

    Type I Hilltop Inflation and the Refined Swampland Criteria

    Chia-Min Lin🇹🇼

    In this paper, I show that type I hilltop inflation under the current observational constaints could have $M_P^2\frac{V^{\prime \prime }}{V}\sim -\mathcal{O}(10^{-2})$ in the parameter space which is in tension with the refined swampland criteria. On the other hand, $M_P^2\frac{V^{\prime \prime }}{V}\sim -\mathcal{O}(1)$ can be achieved if type I hilltop inflation on the brane is considered.

    ↳ astro-ph.COhep-phhep-thPRD(2019)·57 citations
30. 30*

    Moments of pion distribution amplitude using operator product expansion on the lattice

    William Detmold🇺🇸 · Issaku Kanamori🇯🇵 · C.-J. David Lin🇹🇼 · Santanu Mondal🇹🇼 · Yong Zhao🇺🇸

    We report an exploratory study of the current-current matrix elements that are relevant to the extraction of moments of the pion light-cone distribution amplitude, employing the method of introducing a valence relativistic heavy quark. The numerical investigation is carried out in the quenched approximation with the physical volume $L\approx 2.4$ fm at two values of lattice spacing (0.05 and 0.075 fm). We obtain clean signals for the relevant Euclidean hadronic tensor with reasonable statistics, but observe that the lattice artefacts are non-negligible in our results. The key conclusion from the analysis hitherto is that although our approach has the potential for making significant contributions to parton physics, data at finer lattice spacings that are currently being produced are needed in order to control the continuum extrapolation.

    ↳ hep-lathep-phPoS(2018)·36 citations
31. 31*

    The Primordial Black Hole Dark Matter - LISA Serendipity

    N. Bartolo🇮🇹 · V. De Luca🇨🇭 · G. Franciolini🇨🇭 · A. Lewis🇬🇧 · M. Peloso🇮🇹 · A. Riotto🇨🇭

    There has recently been renewed interest in the possibility that the dark matter in the universe consists of primordial black holes (PBHs). Current observational constraints leave only a few PBH mass ranges for this possibility. One of them is around $10^{-12}{M}_{\odot }$. If PBHs with this mass are formed due to an enhanced scalar-perturbation amplitude, their formation is inevitably accompanied by the generation of gravitational waves (GWs) with frequency peaked in the mHz range, precisely around the maximum sensitivity of the LISA mission. We show that, if these primordial black holes are the dark matter, LISA will be able to detect the associated GW power spectrum. Although the GW source signal is intrinsically non-Gaussian, the signal measured by LISA is a sum of the signal from a large number of independent sources suppressing the non-Gaussianity at detection to an unobservable level. We also discuss the effect of the GW propagation in the perturbed universe. PBH dark matter generically leads to a detectable, purely isotropic, Gaussian and unpolarised GW signal, a prediction that is testable with LISA.

    ↳ astro-ph.COgr-qchep-phhep-thPRL(2019)·278 citations
32. 32*

    Testing Primordial Black Holes as Dark Matter through LISA

    N. Bartolo🇮🇹 · V. De Luca🇨🇭 · G. Franciolini🇨🇭 · M. Peloso🇮🇹 · D. Racco🇨🇦 · A. Riotto🇨🇭

    The idea that primordial black holes (PBHs) can comprise most of the dark matter of the universe has recently reacquired a lot of momentum. Observational constraints, however, rule out this possibility for most of the PBH masses, with a notable exception around $10^{-12}{M}_{\odot }$. These light PBHs may be originated when a sizeable comoving curvature perturbation generated during inflation re-enters the horizon during the radiation phase. During such a stage, it is unavoidable that gravitational waves (GWs) are generated. Since their source is quadratic in the curvature perturbations, these GWs are generated fully non-Gaussian. Their frequency today is about the mHz, which is exactly the range where the LISA mission has the maximum of its sensitivity. This is certainly an impressive coincidence. We show that this scenario of PBHs as dark matter can be tested by LISA by measuring the GW two-point correlator. On the other hand, we show that the short observation time (as compared to the age of the universe) and propagation effects of the GWs across the perturbed universe from the production point to the LISA detector suppress the bispectrum to an unobservable level. This suppression is completely general and not specific to our model.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2019)·259 citations
33. 33*

    Dark Matter Searches at Colliders

    Antonio Boveia🇺🇸 · Caterina Doglioni🇸🇪

    Colliders, among the most successful tools of particle physics, have revealed much about matter. This review describes how colliders contribute to the search for particle dark matter, focusing on the highest-energy collider currently in operation, the Large Hadron Collider (LHC) at CERN. In the absence of hints about the character of interactions between dark matter and standard matter, this review emphasizes what could be observed in the near future, presents the main experimental challenges, and discusses how collider searches fit into the broader field of dark matter searches. Finally, it highlights a few areas to watch for the future LHC program.

    ↳ hep-exhep-phAnn.Rev.Nucl.Part.Sci.(2018)·304 citations
34. 34*

    Study of doubly heavy tetraquarks in Lattice QCD

    Parikshit Junnarkar🇮🇳 · Nilmani Mathur🇮🇳 · M Padmanath🇩🇪

    We present results of a lattice calculation of tetraquark states with quark contents $q_1{q}_2\bar{Q}\bar{Q},q_1,q_2\subset u,d,s,c$ and $Q\equiv b,c$ in both spin zero ($J=0$) and spin one ($J=1$) sectors. These calculations are performed on three dynamical $N_f=2+1+1$ highly improved staggered quark ensembles at lattice spacings of about 0.12, 0.09 and 0.06 fm. We use the overlap action for light to charm quarks while a non-relativistic action with non-perturbatively improved coefficients with terms up to $\mathcal{O}({\alpha }_s{v}^4)$ is employed for the bottom quark. While considering two heavy quarks as charm or bottom, we calculate the energy levels of various four-quark configurations with light quark masses ranging from the physical strange quark mass to that of the corresponding physical pion mass. Results for the spin one states show the presence of ground state energy levels which are below their respective thresholds for all the light flavor combinations with both doubly heavy quarks and particularly for the bottom quarks. Further, we identify a trend that the energy splittings, defined as the energy difference between the ground state energy levels and their respective thresholds, increase with decreasing the light quark masses and are maximum at the physical point for all the spin one states. The rate of increase is however dependent on the light quark configuration of the particular spin one state. We also present a study of hadron mass relations involving tetraquarks, baryons and mesons arising in the limit of infinitely heavy quark and find that these relations are more compatible with the heavy quark limit in the bottom sector but deviate substantially in the charm sector. The ground state spectra of the spin zero tetraquark states with various flavor combinations are seen to lie above their respective thresholds.

    ↳ hep-lathep-phPRD(2019)·239 citations
35. 35*

    Expanding Universe and Dynamical Compactification Using Yang-Mills Instantons

    Kyung Kiu Kim🇰🇷 · Seoktae Koh🇰🇷 · Hyun Seok Yang🇰🇷

    We consider an eight-dimensional Einstein-Yang-Mills theory to explore whether Yang-Mills instantons formed in extra dimensions can induce the dynamical instability of our four-dimensional spacetime. We show that the Yang-Mills instantons in extra dimensions can trigger the expansion of our universe in four-dimensional spacetime as well as the dynamical compactification of extra dimensions. We also discuss a possibility to realize a reheating mechanism via the quantum back-reaction from the contracting tiny internal space with a smeared instanton.

    ↳ hep-thgr-qchep-phJHEP(2018)·15 citations
36. 36*

    Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way

    Lina Necib🇺🇸 · Mariangela Lisanti🇺🇸 · Shea Garrison-Kimmel🇺🇸 · Andrew Wetzel🇺🇸 · Robyn Sanderson🇺🇸 · Philip F. Hopkins🇺🇸 · Claude-André Faucher-Giguère🇺🇸 · Dušan Kereš🇺🇸

    The Gaia era opens new possibilities for discovering the remnants of disrupted satellite galaxies in the Solar neighborhood. If the population of local accreted stars is correlated with the dark matter sourced by the same mergers, one can then map the dark matter distribution directly. Using two cosmological zoom-in hydrodynamic simulations of Milky Way-mass galaxies from the Latte suite of Fire-2 simulations, we find a strong correlation between the velocity distribution of stars and dark matter at the solar circle that were accreted from luminous satellites. This correspondence holds for dark matter that is either relaxed or in kinematic substructure called debris flow, and is consistent between two simulated hosts with different merger histories. The correspondence is more problematic for streams because of possible spatial offsets between the dark matter and stars. We demonstrate how to reconstruct the dark matter velocity distribution from the observed properties of the accreted stellar population by properly accounting for the ratio of stars to dark matter contributed by individual mergers. After demonstrating this method using the Fire-2 simulations, we apply it to the Milky Way and use it to recover the dark matter velocity distribution associated with the recently discovered stellar debris field in the Solar neighborhood. Based on results from Gaia, we estimate that $42_{-22}^{+26}\%$ of the local dark matter that is accreted from luminous mergers is in debris flow.

    ↳ astro-ph.GAastro-ph.COhep-ph96 citations
37. 37*

    ${\gamma }^{\ast }\gamma \to \eta ,{\eta }^{\prime }$ transition form factors

    Minghui Ding🇮🇹 · Khepani Raya🇨🇳 · Adnan Bashir🇲🇽 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Muyang Chen🇨🇳 · Craig D. Roberts🇺🇸

    Using a continuum approach to the hadron bound-state problem, we calculate ${\gamma }^{\ast }\gamma \to \eta ,{\eta }^{\prime }$ transition form factors on the entire domain of spacelike momenta, for comparison with existing experiments and in anticipation of new precision data from next-generation $e^{+}{e}^{-}$ colliders. One novel feature is a model for the contribution to the Bethe-Salpeter kernel deriving from the non-Abelian anomaly, an element which is crucial for any computation of $\eta ,{\eta }^{\prime }$ properties. The study also delivers predictions for the amplitudes that describe the light- and strange-quark distributions within the $\eta ,{\eta }^{\prime }$. Our results compare favourably with available data. Important to this at large-$Q^2$ is a sound understanding of QCD evolution, which has a visible impact on the ${\eta }^{\prime }$ in particular. Our analysis also provides some insights into the properties of $\eta ,{\eta }^{\prime }$ mesons and associated observable manifestations of the non-Abelian anomaly.

    ↳ nucl-thhep-exhep-lathep-ph+1PRD(2019)·83 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.