Fri·Dec 14, 2018Friday·December 14, 2018

1. 01*

   Lepton Number and Expansion of the Universe

   Cheng Tao Yang🇺🇸 · Jeremiah Birrell🇺🇸 · Johann Rafelski🇺🇸

   We show that the non-integer effective number of neutrinos $N_{\nu }^{\mathrm{eff}}$ can be understood as an effect of lepton $L$ asymmetry in the early Universe carried by the Dirac neutrino cosmic background. We show that $N_{\nu }^{\mathrm{eff}}=3.36\pm 0.34$ (CMB only) and $N_{\nu }^{\mathrm{eff}}=3.62\pm 0.25$ (CMB and $H_0$) require a ratio between baryon number $B$ and lepton number to be $1.16\times 10^{-9}⩽B/|L|⩽1.51\times 10^{-9}$. These values are close to the baryon-to-photon ratio $0.57\times 10^{-9}⩽B/N_{\gamma }⩽0.67\times 10^{-9}$. Thus instead of the usual $|L|\ll N_{\gamma }$ and $B\simeq |L|$, we propose to use $0.4⩽|L|/N_{\gamma }⩽0.52$ and $B\ll |L|$ as another natural choice, which resolves the tension between Planck-CMB and $H_0$ and leads to a non-integer value of $N_{\nu }^{\mathrm{eff}}>3$.

   hep-phastro-ph.CO4 citations
2. 02*

   Confronting the neutralino and chargino sector of the NMSSM to the multi-lepton searches at the LHC

   Florian Domingo🇩🇪 · Jong Soo Kim🇿🇦 · Victor Martin-Lozano🇩🇪 · Pablo Martin-Ramiro🇪🇸 · Roberto Ruiz de Austri🇪🇸

   We test the impact of the ATLAS and CMS multi-lepton searches performed at the LHC with 8 as well as 13 TeV center-of-mass energy (using only the pre-2018 results) on the chargino and neutralino sector of the NMSSM. Our purpose consists in analyzing the actual reach of these searches for a full model and in emphasizing effects beyond the MSSM that affect the performance of current (MSSM-inspired) electroweakino searches. To this end, we consider several scenarios characterizing specific features of the NMSSM electroweakino sector. We then perform a detailed collider study, generating Monte-Carlo events through Pythia and testing against current LHC constraints implemented in the public tool CheckMATE. We find e.g. that SUSY decay chains involving intermediate singlino or Higgs-singlet states can modify the naive MSSM-like picture of the constraints by inducing final-states with softer or less-easily identifiable SM particles -- reversely, a compressed configuration with singlino NLSP occasionally induces final states that are rich with photons, which could provide complementary search channels.

   hep-phPRD(2020)·25 citations
3. 03*

   Probing Lepton Universality with (Semi)-Leptonic B decays

   Giovanni Banelli🇳🇱 · Robert Fleischer🇳🇱 · Ruben Jaarsma🇳🇱 · Gilberto Tetlalmatzi-Xolocotzi🇳🇱

   The most recent measurements of the observables $R_{D^{(\ast )}}$ are in tension with the Standard Model offering hints of New Physics in $b\to c\ell {\bar{\nu }}_{\ell }$ transitions. Motivated by these results, in this work we present an analysis on their $b\to u\ell {\bar{\nu }}_{\ell }$ counterparts (for $\ell =e,\mu ,\tau$). Our study has three main objectives. Firstly, using ratios of branching fractions, we assess the effects of beyond the Standard Model scalar and pseudoscalar particles in leptonic and semileptonic $B$ decays ($B^{-}\to {\ell }^{-}{\bar{\nu }}_{\ell }$, $\bar{B}\to \pi \ell {\bar{\nu }}_{\ell }$ and $\bar{B}\to \rho \ell {\bar{\nu }}_{\ell }$). Here a key role is played by the leptonic $B$ processes, which are highly sensitive to new pseudoscalar interactions. In particular, we take advantage of the most recent measurement of the branching fraction of the channel $B^{-}\to {\mu }^{-}{\bar{\nu }}_{\mu }$ by the Belle collaboration. Secondly, we extract the CKM matrix element $|V_{ub}|$ while accounting simultaneously for New Physics contributions. Finally, we provide predictions for the branching fractions of yet unmeasured leptonic and semileptonic $B$ decays.

   hep-phSciPost Phys.Proc.(2019)·3 citations
4. 04*

   Seven largest couplings of the standard model as IR fixed points

   Radovan Dermisek🇺🇸 · Navin McGinnis🇺🇸

   We report on an intriguing observation that the values of all the couplings in the standard model except those related to first two generations can be understood from the IR fixed point structure of renormalization group equations in the minimal supersymmetric model extended by one complete vectorlike family with the scale of new physics in a multi-TeV range.

   hep-phPRL(2019)·9 citations
5. 05*

   Heavy quark diffusion in a Polyakov loop plasma

   Balbeer Singh🇮🇳 · Aman Abhishek🇮🇳 · Santosh K Das🇮🇳 · Hiranmaya Mishra🇮🇳

   We calculate the transport coefficients, drag and momentum diffusion, of a heavy quark in a thermalized plasma of light quarks in the background of Polyakov loop. Quark thermal mass and the gluon Debye mass are calculated in a non-trivial Polyakov loop background. The constituent quark masses and the Polyakov loop is estimated within a Polyakov loop quark meson (PQM) model. The relevant scattering amplitudes for heavy quark and light partons in the background of Polyakov loop has been estimated within the matrix model. We have also compared the results with the Polyakov loop parameter estimated from lattice QCD simulations. We have studied the temperature and momentum dependence of heavy quark drag and diffusion coefficients. It is observed that the temperature dependence of the drag coefficient is quite weak which may play a key role to understand heavy quark observables at RHIC and LHC energies.

   hep-phPRD(2019)·21 citations
6. 06*

   The role of the thermal $f_0(500)$ or sigma in chiral symmetry restoration

   A. Vioque-Rodríguez🇪🇸 · A. Gómez Nicola🇪🇸

   We analyze the $f_0(500)$ state generated as a pole of $\pi \pi$ scattering within unitarized low-energy effective theories at finite temperature. First, we report on the $\sigma$ self-energy in the LSM, which is used as a benchmark in order to test the hypotheses carried out. The relation of that thermal pole with the scalar susceptibility is studied within a scalar saturation approach, which yields results complying with lattice data. The robustness and predictability of this method are studied in terms of the low-energy constants involved and the unitarization method. Our analysis highlights the importance of this thermal state to describe the main qualitative features of the scalar susceptibility around the chiral transition.

   hep-phPoS(2018)·0 citations
7. 07*

   Generation patterns, modified $\gamma -Z$ mixing, and hidden sector with dark matter candidates as framed standard model results

   José BORDES (Departament Fisica Teorica and IFIC, Universitat de Valencia-CSIC, Spain)🇪🇸 · CHAN Hong-Mo (Rutherford Appleton Laboratory, United Kingdom)🇬🇧 · TSOU Sheung Tsun (Mathematical Institute, University of Oxford, United Kingdom)🇬🇧

   A descriptive summary is given of the results to-date from the framed standard model (FSM) which: (i) assigns geometric meaning to the Higgs field and to fermion generations, hence offering an explanation for the observed mass and mixing patterns of quarks and leptons, reproducing near-quantitatively 17 of SM parameters with only 7, (ii) predicts a new vector boson $G$ which mixes with $\gamma$ and $Z$, leading to deviations from the SM mixing scheme. For $m_G>1$ TeV, these deviations are within present experimental errors but should soon be detectable at LHC when experimental accuracy is further improved, (iii) suggests the existence of a hidden sector of particles as yet unknown to experiment which interact but little with the known particles. The lowest members of the hidden sector of mass around 17 MeV, being electrically neutral and stable, may figure as dark matter constituents. The idea is to retrace the steps leading to the above results unencumbered by details already worked out and reported elsewhere. This has helped to clarify the logic, tighten some arguments and dispense with one major assumption previously thought necessary, thus strenthening earlier results in opening up possibly a new and exciting vista for further exploration.

   hep-phInt.J.Mod.Phys.A(2019)·4 citations
8. 08*

   A new pQCD based Monte Carlo event generator for jets in the quark-gluon plasma

   Paul Caucal🇫🇷 · Edmond Iancu🇫🇷 · Alfred H. Mueller🇺🇸 · Gregory Soyez🇫🇷

   A main difficulty in understanding the dynamics of jets produced in the high-density environment of ultrarelativistic heavy ion collision, is to provide a unified description for the two sources of radiation that are a priori expected: the "vacuum-like" emissions responsible for the parton shower from large virtualities down to the hadronisation scale and the "medium-induced" emissions responsible for the energy loss by the jet. In the recent paper arXiv:1801.09703, we demonstrated that these two mechanisms can be factorized from each other within a controlled, "double-logarithmic" approximation in perturbative QCD. In this proceeding we recall the main features of the jet evolution in a dense QCD medium. We emphasize that the in-medium parton showers differ from those in the vacuum in two crucial aspects: their phase-space is reduced and the first emission outside the medium can violate angular ordering. Based on this factorized picture, which is Markovian, we have recently developed a Monte Carlo event generator which includes both vacuum-like and medium-induced emissions and goes beyond the double logarithmic approximation. We here present our first results for the fragmentation function and the energy loss by the jet.

   hep-phnucl-thPoS(2019)·12 citations
9. 09*

   How light the lepton flavor changing gauge bosons can be?

   Zurab Berezhiani🇮🇹 · Benedetta Belfatto🇮🇹

   Spontaneous breaking of inter-family (horizontal) gauge symmetries can be at the origin of the mass hierarchy between the fermion families. The corresponding gauge bosons have flavor-nondiagonal couplings which generically induce the flavour changing phenomena, and this puts strong lower limits on the flavor symmetry breaking scales. However, in the special choices of chiral horizontal symmetries the flavor changing effects can be naturally suppressed. For the sake of demonstration, we consider the case of leptonic gauge symmetry $SU(3{)}_e$ acting between right-handed leptons and show that the respective gauge bosons can have mass in the TeV range, without contradicting the existing experimental limits.

   hep-phEPJC(2019)·19 citations
10. 10*

    Impact of CMS dijets in 5.02 TeV pPb and pp collisions on EPPS16 nuclear PDFs

    Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮

    The CMS measurement of dijet pseudorapidity distributions in pPb versus pp collisions at 5.02 TeV provides a direct probe on nuclear gluon PDFs. We show that while the predicted pPb pseudorapidity distributions suffer from sizable free-proton PDF uncertainties, the ratios of the pPb and pp distributions are practically insensitive to scale and free-proton PDF choices. We find the CMS data on pPb to pp ratios to be in good agreement with the EPPS16 nuclear modifications. Using a non-quadratic extension of the Hessian PDF reweighting method, we study the impact of these data on the EPPS16 nuclear PDFs. Relative to EPPS16, we find stronger evidence for mid-x gluon antishadowing as well as indication for larger gluon shadowing at small x. The data are also able to further constrain the gluon PDF in the EMC region.

    hep-phPoS(2019)·4 citations
11. 11*

    Axion-electrodynamics: a quantum field calculation

    Marc Beutter🇩🇪 · Andreas Pargner🇩🇪 · Thomas Schwetz🇩🇪 · Elisa Todarello🇩🇪

    An axion background field induces tiny oscillating electric and magnetic fields in an external static magnetic field. This signature is used to search for axion dark matter. We use standard quantum field theory techniques to obtain an expression for a transition amplitude, from which we identify the classical electromagnetic fields induced by the background axion field. We confirm previous results, that if the spatial size $R$ of the applied static magnetic field is small compared to the axion Compton wavelength $\lambda$, the induced electric and magnetic fields are parametrically suppressed by the small numbers $(R/\lambda {)}^2$ and $R/\lambda$, respectively, relative to the case when $R$ is larger than $\lambda$. Our approach allows an intuitive interpretation in terms of 4-momentum conservation and momentum exchange via the photon propagator.

    hep-phJCAP(2019)·42 citations
12. 12*

    New Physics Suggested by Atomki Anomaly

    Luigi Delle Rose🇮🇹 · Shaaban Khalil🇪🇬 · Simon J.D. King🇬🇧 · Stefano Moretti🇬🇧

    We consider several extensions of the Standard Model (SM) which can explain the anomalies observed by the Atomki collaboration in the decay of excited states of Beryllium via a new boson with a mass around 17 MeV yielding $e^{+}{e}^{-}$ pairs. We show how both spin-0 and 1 solutions are possible and describe the Beyond the SM (BSM) scenarios that can accommodate these. They include BSM frameworks with either an enlarged Higgs, or gauge sector, or both.

    hep-phFront.in Phys.(2019)·36 citations
13. 13*

    Minimal radiative Dirac neutrino mass models

    Julian Calle🇨🇴 · Diego Restrepo🇨🇴 · Carlos E. Yaguna🇨🇴 · Óscar Zapata🇨🇴

    Neutrinos may be Dirac particles whose masses arise radiatively at one-loop, naturally explaining their small values. In this work we show that all the one-loop realizations of the dimension-five operator to effectively generate Dirac neutrino masses can be implemented by using a single local symmetry: $U(1{)}_{B-L}$. Since this symmetry is anomalous, new chiral fermions, charged under $B-L$, are required. The minimal model consistent with neutrino data includes three chiral fermions, two of them with the same lepton number. The next minimal models contain five chiral fermions and their $B-L$ charges can be fixed by requiring a dark matter candidate in the spectrum. We list the full particle content as well as the relevant Lagrangian terms for each of these models. They are new and simple models that can simultaneously accommodate Dirac neutrino masses (at one-loop) and dark matter without invoking any discrete symmetries.

    hep-phPRD(2019)·58 citations
14. 14*

    Dark matter from CP symmetry of order 4: evolution in the asymmetric regime

    Igor P. Ivanov🇵🇹 · Maxim Laletin🇧🇪

    Multi-Higgs models equipped with global symmetries produce scalar dark matter (DM) candidates stabilized by the unbroken symmetry. It is remarkable that a conserved CP symmetry can also stabilize DM candidates, provided it is a CP symmetry of order higher than two. CP4 3HDM, the three-Higgs-doublet model with CP symmetry of order 4, is the simplest example of this kind. It contains two mass-degenerate scalar DM candidates $\phi$ and $\bar{\phi }$, each of them being a CP4 eigenstate and, therefore, its own antiparticle. A novel phenomenological feature of this model is the presence of $\phi \phi \leftrightarrow \bar{\phi }\bar{\phi }$ conversion process, which conserves CP. It offers a rare example of DM models in which self-interaction in the dark sector can significantly affect cosmological and astrophysical observables. Here, we explore the thermal evolution of these DM species in the asymmetric regime. We assume that a mechanism external to CP4 3HDM produces an initial imbalance of the densities of $\phi$ and $\bar{\phi }$. As the Universe cools down, we track the evolution of the asymmetry through different stages, and determine how the final asymmetry depends on the interplay between the conversion and annihilation $\phi \bar{\phi }\to$ SM and on the initial conditions. We begin with the analytic treatment of Boltzmann equations, present a detailed qualitative description of the process, and then corroborate it with numerical results obtained using a dedicated computer code. Finally, we check if the model can produce an observable indirect detection signal.

    hep-phastro-ph.COJCAP(2019)·10 citations
15. 15*

    IceCube Flavor Ratios with Identified Astrophysical Sources: Towards Improving New Physics Testability

    Vedran Brdar🇩🇪 · Rasmus S. L. Hansen🇩🇪

    Motivated by the discovery of the first high-energy astrophysical neutrino source, the blazar TXS 0506+056, we revisit the IceCube flavor ratio analysis. Assuming large statistics from identified blazars, collected in the forthcoming years by the IceCube detector and its successor IceCube-Gen2, we demonstrate that the constraints on several new physics scenarios in which the baseline dependent terms in neutrino oscillation probabilities are not averaged, can be improved. As a representative case, we consider pseudo-Dirac neutrinos while neutrino decay is also discussed.

    hep-phastro-ph.HEJCAP(2019)·32 citations
16. 16*

    Geoneutrinos in Large Direct Detection Experiments

    Graciela B. Gelmini🇺🇸 · Volodymyr Takhistov🇺🇸 · Samuel J. Witte🇪🇸

    Geoneutrinos can provide a unique insight into Earth's interior, its central engine and its formation history. We study the detection of geoneutrinos in large direct detection experiments, which has been considered non-feasible. We compute the geoneutrino-induced electron and nuclear recoil spectra in different materials, under several optimistic assumptions. We identify germanium as the most promising target element due to the low nuclear recoil energy threshold that could be achieved. The minimum exposure required for detection would be $\mathcal{O}(10)$ tonne-years. The realistic low thresholds achievable in germanium and silicon permit the detection of ${}^{40}$K geoneutrinos. These are particularly important to determine Earth's formation history but they are below the kinematic threshold of inverse beta decay, the detection process used in scintillator-based experiments.

    hep-phhep-exphysics.geo-phPRD(2019)·32 citations
17. 17*

    Photon-photon scattering in the resonance region at midrapidity at the LHC

    R.Schicker🇩🇪 · Mariola Klusek-Gawenda🇵🇱 · A. Szczurek🇵🇱

    A study is presented to extend the measurements of photon-photon scattering in ultra-peripheral Pb-Pb collisions at the LHC into the mass region of the pseudoscalar resonances $\eta$ and ${\eta }^{\prime }$. The elementary photon-photon scattering cross section is presented. The cross section for photon-photon scattering in Pb-Pb is derived by convoluting the elementary photon-photon cross section with the Pb-Pb photon luminosity. The main background to two-photon final states, arising from double ${\pi }^0$ production with two of the four decay photons escaping detection, is examined, and possible kinematical conditions are discussed to optimize the signal-to-background ratio for such measurements at mid-rapidity.

    hep-phnucl-exActa Phys.Polon.Supp.(2019)·0 citations
18. 18*

    The equivalent vector boson approximation at threshold energies

    I. Alikhanov🇷🇺

    A simple derivation of the distributions of the equivalent electroweak vector bosons in leptons and quarks is presented. The applicability of the equivalent vector boson approximation at relatively low energies close to the $W$ and $Z$ boson thresholds is demonstrated. It is shown that the threshold correction to the distribution functions emerges naturally in the theory. Implications of the results for processes with the emission of the gauge bosons are discussed.

    hep-ph4 citations
19. 19*

    Polarized baryon production in heavy ion collisions: an analytic hydrodynamical study

    Balint Boldizsar🇭🇺 · Marton I. Nagy🇭🇺 · Mate Csanad🇭🇺

    We utilize known exact analytic solutions of perfect fluid hydrodynamics to analytically calculate the polarization of baryons produced in heavy ion collisions. Assuming local thermodynamical equilibrium also for spin degrees of freedom, baryons get a net polarization at their formation (freeze-out). This polarization depends on the time evolution of the Quark-Gluon Plasma (QGP), which can be described as an almost perfect fluid. By using exact analytic solutions, we thus can analyze the necessity of rotation (and vorticity) for non-zero net polarization. In this paper we give the first analytical calculations for the polarization four-vector. We use two hydrodynamical solutions; one is the spherically symmetric Hubble flow (a somewhat oversimplified model, to demonstrate the methodology). The other solution which we use is a somewhat more involved one that corresponds to a rotating and accelerating expansion, and is thus well suited to investigate some main features of the time evolution of the QGP created in peripheral heavy-ion collisions (although there are still many numerous features of a real collision geometry that are beyond the reach of this simple model). Finally we illustrate and discuss our results on the polarization.

    hep-phnucl-thUniverse(2019)·8 citations
20. 20*

    Long Live the Higgs Factory: Higgs Decays to Long-Lived Particles at Future Lepton Colliders

    Samuel Alipour-Fard🇺🇸 · Nathaniel Craig🇺🇸 · Minyuan Jiang🇺🇸 · Seth Koren🇺🇸

    We initiate the study of exotic Higgs decays to long-lived particles (LLPs) at proposed future lepton colliders, focusing on scenarios with displaced hadronic final states. Our analysis entails a realistic tracker-based search strategy involving the reconstruction of displaced secondary vertices and the imposition of selection cuts appropriate for eliminating the largest irreducible backgrounds. The projected sensitivity is broadly competitive with that of the LHC and potentially superior at lower LLP masses. In addition to forecasting branching ratio limits, which may be freely interpreted in a variety of model frameworks, we interpret our results in the parameter space of a Higgs portal Hidden Valley and various incarnations of neutral naturalness, illustrating the complementarity between direct searches for LLPs and precision Higgs coupling measurements at future lepton colliders.

    hep-phCPC(2019)·52 citations
21. 21*

    Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise $N_{\mathrm{eff}}$ evaluation

    Miguel Escudero🇬🇧

    The number of effective relativistic neutrino species represents a fundamental probe of the thermal history of the early Universe, and as such of the Standard Model of Particle Physics. Traditional approaches to the neutrino decoupling are either very technical and computationally expensive, or assume that neutrinos decouple instantaneously. In this work, we aim to fill the gap between these two approaches by modeling the neutrino decoupling in terms of two simple coupled differential equations for the electromagnetic and neutrino sector temperatures, in which all the relevant interactions are taken into account and which allows for a straightforward implementation of BSM species. Upon including finite temperature QED corrections we reach an accuracy on $N_{\mathrm{eff}}$ in the SM of $0.01$. We illustrate the usefulness of this approach to the neutrino decoupling by considering, in a model independent manner, the impact of MeV thermal dark matter on $N_{\mathrm{eff}}$. We show that Planck rules out electrophilic and neutrinophilic thermal dark matter particles of $m<3.0\text{MeV}$ at 95\% CL regardless of their spin, and of their annihilation being $s$-wave or $p$-wave. We point out that thermal dark matter particles with non-negligible interactions with both electrons and neutrinos are more elusive to CMB observations than purely electrophilic or neutrinophilic ones. In addition, assisted by the accuracy of our approach, we show that CMB Stage-IV experiments will generically test thermal dark matter particles with $m\lesssim 15\text{MeV}$. We make publicly available the codes developed for this study at https://github.com/MiguelEA/nudec_BSM .

    hep-phastro-ph.COJCAP(2019)·202 citations
22. 22*

    A Module For Boosted Dark Matter Event Generation in GENIE

    Joshua Berger🇺🇸

    Models that produce a flux of semi-relativistic or relativistic boosted dark matter at large neutrino detectors are well-motivated extensions beyond the minimal weakly interacting massive particle (WIMP) paradigm. Current and upcoming liquid argon time projection chamber (LArTPC) based detectors will have improved sensitivity to such models, but also require improved theoretical modeling to better understand their signals and optimize their analyses. I present the first full Monte Carlo tool for boosted dark matter interacting with nuclei in the energy regime accessible to LArTPC detectors, including the Deep Underground Neutrino Experiment (DUNE). The code uses the nuclear and strong physics modeling of the GENIE neutrino Monte Carlo event generator with particle physics modeling for dark matter. The code will be available in GENIE v3. In addition, I present a code for generating a GENIE-compatible flux of boosted dark matter coming from the Sun that is released independently.

    hep-phhep-ex22 citations
23. 23*

    Nuclear structure factors for general spin-independent WIMP-nucleus scattering

    Martin Hoferichter🇺🇸 · Philipp Klos🇩🇪 · Javier Menéndez🇯🇵 · Achim Schwenk🇩🇪

    We present nuclear structure factors that describe the generalized spin-independent coupling of weakly interacting massive particles (WIMPs) to nuclei. Our results are based on state-of-the-art nuclear structure calculations using the large-scale nuclear shell model. Starting from quark- and gluon-level operators, we consider all possible coherently enhanced couplings of spin-1/2 and spin-0 WIMPs to one and two nucleons up to third order in chiral effective field theory. This includes a comprehensive discussion of the structure factors corresponding to the leading two-nucleon currents covering, for the first time, the contribution of spin-2 operators. We provide results for the most relevant nuclear targets considered in present and planned dark matter direct detection experiments: fluorine, silicon, argon, and germanium, complementing our previous work on xenon. All results are also publicly available in a Python notebook.

    hep-phhep-exhep-latnucl-thPRD(2019)·100 citations
24. 24*

    $SU(5)$ Grand Unified Theory with $A_4$ Modular Symmetry

    Francisco J. de Anda🇲🇽 · Stephen F. King🇬🇧 · Elena Perdomo🇬🇧

    We present the first example of a grand unified theory (GUT) with a modular symmetry interpreted as a family symmetry. The theory is based on supersymmetric $SU(5)$ in 6d, where the two extra dimensions are compactified on a $T_2/{\mathbb{Z}}_2$ orbifold. We have shown that, if there is a finite modular symmetry, then it can only be $A_4$ with an (infinite) discrete choice of moduli, where we focus on $\tau =\omega =e^{i2\pi /3}$, the unique solution with $|\tau |=1$. The fields on the branes respect a generalised CP and flavour symmetry $A_4⋉{\mathbb{Z}}_2$ which is isomorphic to $S_4$ which leads to an effective $\mu -\tau$ reflection symmetry at low energies, implying maximal atmospheric mixing and maximal leptonic CP violation. We construct an explicit model along these lines with two triplet flavons in the bulk, whose vacuum alignments are determined by orbifold boundary conditions, analogous to those used for $SU(5)$ breaking with doublet-triplet splitting. There are two right-handed neutrinos on the branes whose Yukawa couplings are determined by modular weights. The charged lepton and down-type quarks have diagonal and hierarchical Yukawa matrices, with quark mixing due to a hierarchical up-quark Yukawa matrix.

    hep-phPRD(2020)·189 citations
25. 25*

    A new reduction strategy for special negative sectors of planar two-loop integrals without Laporta algorithm

    Adam Kardos🇭🇺

    In planar two-loop integrals there is a dedicated sector such that when its index is zero, the two-loop integral decomposes into the product of two one-loop integrals. We show an alternative reduction strategy for these sectors when their index is negative using the Baikov representation. This reduction strategy is free from the Laporta algorithm. It follows a top-down approach and is much faster than approaches based on the brute-force, conventional integration by parts identities.

    hep-ph8 citations
26. 26*

    Yukawa Unification with light supersymmetric particles consistent with LHC constraints

    Mureed Hussain🇵🇰 · Rizwan Khalid🇵🇰

    We investigate supersymmetric models with left-right symmetry based on the group $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ ($4$-$2$-$2$) with negative sign of bilinear Higgs potential parameter $\mu$ in the context of the latest experimental results. In the backdrop of experimental results from the Large Hadron Collider, we investigate the possibility of Yukawa unification in $4$-$2$-$2$ and find out the same is still not ruled out. Furthermore, this scenario also provides a satisfactory dark matter candidate. The current experimental bounds on sparticle masses, mass bounds on Higgs particle, updated phenomenological constraints from the rare decays of B meson and the anomalous magnetic moment of muon with the requirement of a Yukawa unified theory having $10\%$ or better third family Yukawa unification are utilized to bound the parametric space of these models.

    hep-phNPB(2019)·6 citations
27. 27*

    Suppression of light nuclei production in collisions of small systems at the Large Hadron Collider

    Kai-Jia Sun🇺🇸 · Che Ming Ko🇺🇸 · Benjamin Dönigus🇩🇪

    We show that the recently observed suppression of the yield ratio of deuteron to proton and of helium-3 to proton in p+p collisions compared to those in p+Pb or Pb+Pb collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) can be explained if light nuclei are produced from the coalescence of nucleons at the kinetic freeze-out of these collisions. This suppression is attributed to the non-negligible sizes of deuteron and helium-3 compared to the size of the nucleon emission source in collisions of small systems, which reduces the overlap of their internal wave functions with those of nucleons. The same model is also used to study the production of triton and hypertriton in heavy-ion collisions at the LHC. Compared to helium-3 in events of low charged particle multiplicity, the triton is less suppressed due to its smaller size and the hypertriton is even more suppressed as a result of its much larger size.

    ↳ nucl-thhep-phnucl-exPLB(2019)·129 citations
28. 28*

    Tracker and scaling solutions in DHOST theories

    Noemi Frusciante🇵🇹 · Ryotaro Kase🇯🇵 · Kazuya Koyama🇬🇧 · Shinji Tsujikawa🇯🇵 · Daniele Vernieri🇵🇹

    In quadratic-order degenerate higher-order scalar-tensor (DHOST) theories compatible with gravitational-wave constraints, we derive the most general Lagrangian allowing for tracker solutions characterized by $\dot{\varphi }/H^p=\mathrm{constant}$, where $\dot{\varphi }$ is the time derivative of a scalar field $\varphi$, $H$ is the Hubble expansion rate, and $p$ is a constant. While the tracker is present up to the cubic-order Horndeski Lagrangian $L=c_{2}X-c_3{X}^{(p-1)/(2p)}\square \varphi$, where $c_2,c_3$ are constants and $X$ is the kinetic energy of $\varphi$, the DHOST interaction breaks this structure for $p\ne 1$. Even in the latter case, however, there exists an approximate tracker solution in the early cosmological epoch with the nearly constant field equation of state $w_{\varphi }=-1-2p\dot{H}/(3H^2)$. The scaling solution, which corresponds to $p=1$, is the unique case in which all the terms in the field density ${\rho }_{\varphi }$ and the pressure $P_{\varphi }$ obey the scaling relation ${\rho }_{\varphi }\propto P_{\varphi }\propto H^2$. Extending the analysis to the coupled DHOST theories with the field-dependent coupling $Q(\varphi )$ between the scalar field and matter, we show that the scaling solution exists for $Q(\varphi )=1/({\mu }_1\varphi +{\mu }_2)$, where ${\mu }_1$ and ${\mu }_2$ are constants. For the constant $Q$, i.e., ${\mu }_1=0$, we derive fixed points of the dynamical system by using the general Lagrangian with scaling solutions. This result can be applied to the model construction of late-time cosmic acceleration preceded by the scaling $\varphi$-matter-dominated epoch.

    ↳ gr-qcastro-ph.COhep-phhep-thPLB(2019)·33 citations
29. 29*

    Stochastic hydrodynamics and long time tails of an expanding conformal charged fluid

    M. Martinez🇺🇸 · Thomas Schaefer🇺🇸

    We investigate the impact of hydrodynamic fluctuations on correlation functions in a scale invariant fluid with a conserved $U(1)$ charge. The kinetic equations for the two-point functions of pressure, momentum and heat energy densities are derived within the framework of stochastic hydrodynamics. The leading non-analytic contributions to the energy-momentum tensor as well as the $U(1)$ current are determined from the solutions to these kinetic equations. In the case of a static homogeneous background we show that the long time tails obtained from hydro-kinetic equations reproduce the one-loop results derived from statistical field theory. We use these results to establish bounds on transport coefficients. We generalize the stochastic equation to a background flow undergoing Bjorken expansion. We compute the leading fractional power $\mathcal{O}((\tau T{)}^{-3/2})$ correction to the $U(1)$ current and compare with the first order gradient term.

    ↳ hep-thcond-mat.stat-mechhep-phnucl-thPRC(2019)·56 citations
30. 30*

    Constraining power of cosmological observables: blind redshift spots and optimal ranges

    L. Kazantzidis🇬🇷 · L. Perivolaropoulos🇬🇷 · F. Skara🇬🇷

    A cosmological observable measured in a range of redshifts can be used as a probe of a set of cosmological parameters. Given the cosmological observable and the cosmological parameter, there is an optimum range of redshifts where the observable can constrain the parameter in the most effective manner. For other redshift ranges the observable values may be degenerate with respect to the cosmological parameter values and thus inefficient in constraining the given parameter. These are blind redshift ranges. We determine the optimum and the blind redshift ranges of cosmological observables with respect to the cosmological parameters: matter density parameter ${\Omega }_m$, equation of state parameter $w$ and a modified gravity parameter $g_a$ which parametrizes the evolution of an effective Newton's constant. We consider the observables: growth rate of matter density perturbations expressed through $f(z)$ and $f{\sigma }_8$, the distance modulus $\mu (z)$, Baryon Acoustic Oscillation observables $D_V(z)\times \frac{r_s^{fid}}{r_s}$, $H\times \frac{r_s}{r_s^{fid}}$ and $D_A\times \frac{r_s^{fid}}{r_s}$, $H(z)$ measurements and the gravitational wave luminosity distance. We introduce a new statistic $S_P^O(z)\equiv \frac{\Delta O}{\Delta P}(z)\cdot V_{eff}^{1/2}$, including the effective survey volume $V_{eff}$, as a measure of the constraining power of a given observable $O$ with respect to a cosmological parameter $P$ as a function of redshift $z$. We find blind redshift spots $z_b$ ($S_P^O(z_b)\simeq 0$) and optimal redshift spots $z_s$ ($S_P^O(z_s)\simeq max$) for these observables with respect to the parameters ${\Omega }_m$, $w$ and $g_a$. For $O=f{\sigma }_8$ and $P=({\Omega }_m,w,g_a)$ we find blind spots at $z_b\simeq (1,2,2.7)$ respectively and optimal (sweet) spots at $z_s=(0.5,0.8,1.2)$. Thus probing higher redshifts may be less effective than probing lower redshifts with higher accuracy.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·30 citations
31. 31*

    Effects of the surrounding primordial black holes on the merger rate of primordial black hole binaries

    Lang Liu🇨🇳 · Zong-Kuan Guo🇨🇳 · Rong-Gen Cai🇨🇳

    We develop an analytic formalism for computing the merger rate of primordial black hole binaries with a general mass function by taking into account the torques by the surrounding primordial black holes and linear density perturbations. We find that $\alpha =-(m_i+m_j{)}^2{\partial }^2\ln \mathcal{R}(m_i,m_j)/\partial m_i\partial m_j=36/37$ is independent of the mass function. Moreover, the ratio of the merger rate density of primordial black hole binaries by taking into account the torques by the surrounding primordial black holes to by the nearest primordial black hole is independent of the masses of binaries.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·93 citations
32. 32*

    Cosmology-marginalized approaches in Bayesian model comparison: the neutrino mass as a case study

    S. Gariazzo🇪🇸 · O. Mena🇪🇸

    We propose here a \emph{novel} method which singles out the \emph{a priori} unavoidable dependence on the underlying cosmological model when extracting parameter constraints, providing robust limits which only depend on the considered dataset. Interestingly, when dealing with several possible cosmologies and interpreting the Bayesian preference in terms of the Gaussian statistical evidence, the preferred model is much less favored than when only two cases are compared. As a working example, we apply our approach to the cosmological neutrino mass bounds, which play a fundamental role not only in establishing the contribution of relic neutrinos to the dark matter of the Universe, but also in the planning of future experimental searches of the neutrino character and of the neutrino mass ordering.

    ↳ astro-ph.COastro-ph.IMhep-phphysics.data-anPRD(2019)·29 citations
33. 33*

    Two-fluid solutions of particle-creation cosmologies

    Supriya Pan🇮🇳 · John D. Barrow🇬🇧 · Andronikos Paliathanasis🇿🇦

    Cosmological evolution driven incorporating continuous particle creation by the time-varying gravitational field is investigated. We consider a spatially flat, homogeneous and isotropic universe with two matter fluids in the context of general relativity. One fluid is endowed with gravitationally induced `adiabatic' particle creation, while the second fluid simply satisfies the conservation of energy. We show that the dynamics of the two fluids is entirely controlled by a single nonlinear differential equation involving the particle creation rate, $\Gamma (t)$. We consider a very general particle creation rate, $\Gamma (t)$, that reduces to several special cases of cosmological interest, including $\Gamma =$ constant, ($n\in \mathbb{N}$), $\Gamma \propto \exp (1/H)$. Finally, we present singular algebraic solutions of the gravitational field equations for the two-fluid particle creation models and discuss their stability.

    ↳ gr-qcastro-ph.COhep-phEPJC(2019)·30 citations
34. 34*

    Partial Deconfinement

    Masanori Hanada🇬🇧 · Goro Ishiki🇯🇵 · Hiromasa Watanabe🇯🇵

    We argue that the confined and deconfined phases in gauge theories are connected by a partially deconfined phase (i.e. SU(M) in SU(N), where M<N, is deconfined), which can be stable or unstable depending on the details of the theory. When this phase is unstable, it is the gauge theory counterpart of the small black hole phase in the dual string theory. Partial deconfinement is closely related to the Gross-Witten-Wadia transition, and is likely to be relevant to the QCD phase transition. The mechanism of partial deconfinement is related to a generic property of a class of systems. As an instructive example, we demonstrate the similarity between the Yang-Mills theory/string theory and a mathematical model of the collective behavior of ants [Beekman et al., Proceedings of the National Academy of Sciences, 2001]. By identifying the D-brane, open string and black hole with the ant, pheromone and ant trail, the dynamics of two systems closely resemble with each other, and qualitatively the same phase structures are obtained.

    ↳ hep-thhep-lathep-phJHEP(2019)·66 citations
35. 35*

    Primordial power spectra from an emergent universe: basic results and clarifications

    Killian Martineau🇫🇷 · Aurélien Barrau🇫🇷

    Emergent cosmological models, together with the Big Bang and bouncing scenarios, are among the possible descriptions of the early Universe. This work aims at clarifying some general features of the primordial tensor power spectrum in this specific framework. In particular, some naive beliefs are corrected. Using a toy model, we investigate the conditions required to produce a scale invariant spectrum and show to which extent this spectrum can exhibit local features sensitive to the details of the scale factor evolution near the transition time.

    ↳ gr-qcastro-ph.COhep-phUniverse(2018)·15 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.