Mon·Feb 29, 2016Monday·February 29, 2016

1. 01*

   Top Physics in WHIZARD

   J. Reuter🇩🇪 · F. Bach🇩🇪 · B. Chokoufe🇩🇪 · A. Hoang🇦🇹 · W. Kilian🇩🇪 · M. Stahlhofen🇩🇪 · T. Teubner🇬🇧 · C. Weiss🇩🇪

   In this talk we summarize the top physics setup in the event generator WHIZARD with a main focus on lepton colliders. This includes full six-, eight- and ten-fermion processes, factorized processes and spin correlations. For lepton colliders, QCD NLO processes for top quark physics are available and will be discussed. A special focus is on the top-quark pair threshold, where a special implementation combines a non-relativistic effective field theory calculation augmented by a next-to-leading threshold logarithm resummation with a continuum relativistic fixed-order QCD NLO simulation.

   hep-phhep-ex10 citations
2. 02*

   SUSY Fits and their Implications for ILC and CLIC

   S. Heinemeyer🇪🇸

   We review results from our frequentist analysis of the parameter space of the pMSSM10, in which the following 10 soft SUSY-breaking parameters are specified independently at the mean scalar top mass scale Msusy = \sqrt{M_stop1 M_stop2}: the gaugino masses M_{1,2,3}, the 1st-and 2nd-generation squark masses M_squ1 = M_squ2, the third-generation squark mass M_squ3, a common slepton mass M_slep and a common trilinear mixing parameter A, the Higgs mixing parameter mu, the pseudoscalar Higgs mass M_A and tan beta, the ratio of the two Higgs vacuum expectation values. We implemented the LHC searches for strongly- and electroweakly-interacting sparticles and light stops, so as to confront the pMSSM10 parameter space with all relevant SUSY searches. In addition, our analysis includes Higgs mass and rate measurements, SUSY Higgs exclusion bounds, the measurements of \bmm, other B-physics observables, electroweak precision observables, the cold dark matter density and the searches for spin-independent dark matter scattering, assuming that the cold dark matter is mainly provided by the lightest neutralino. We discuss the discovery potential of future e^+e^- linear colliders, such as ILC and CLIC, in the preferred pMSSM10 parameter space.

   hep-ph1 citation
3. 03*

   Neutral Higgs Boson Production at e^+e^- Colliders in the Complex MSSM: Towards the LC Precision

   S. Heinemeyer🇪🇸 · C. Schappacher🇩🇪

   For the search for additional Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses in the Higgs sector a precise knowledge of their production properties is mandatory. We review the evaluation of the cross sections for the neutral Higgs boson production at e^+e^- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanisms e^+e^- -> h_i Z, h_i gamma, h_i h_j (i,j = 1,2,3), including soft and hard QED radiation. The dependence of the Higgs boson production cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many cross sections. They are, depending on the production channel, roughly of 10-20% of the tree-level results, but can go up to 50% or higher.

   hep-ph1 citation
4. 04*

   Physical and invariant models for defect network evolution

   C. J. A. P. Martins🇵🇹 · M. M. P. V. P. Cabral🇵🇹

   We revisit the velocity-dependent one-scale model for topological defect evolution, and present a new alternative formulation in terms of a physical (rather than invariant) characteristic length scale. While the two approaches are equivalent (as we explicitly demonstrate), the new one is particularly relevant when studying the evolution of ultra-relativistic defects. Moreover, a comparison of the two provides further insight on the interpretation of the model's two phenomenological parameters, $c$ related to energy losses and $k$ related to the curvature of the defects. As an illustration of the relevance of the new formulation, we use it to study the evolution of cosmic string and domain wall networks in contracting universes. We show that these networks are ultra-relativistic and conformally contracted, with the physical length scale behaving as $L_{ph}\propto a$ and the density as $\rho \propto a^{-4}$ (as in a radiation fluid) in both cases. On the other hand the velocity and invariant length respectively behave as $(\gamma v)\propto a^{-n}$ and $L_{inv}\propto a^{\frac{4}{4-n}}$, where $n$ is the number of dimensions of the defect's worldsheet. Finally we also study an alternative friction-dominated scenario and show that the stretching and Kibble regimes identified in the case of expanding universes can also occur for contracting ones.

   hep-phastro-ph.COgr-qchep-thPRD(2016)·10 citations
5. 05*

   Measuring light-by-light scattering at the LHC and FCC

   David d'Enterria🇨🇭 · Gustavo G. da Silveira🇧🇷

   Elastic light-by-light scattering, $\gamma \gamma \to \gamma \gamma$, can be measured in electromagnetic interactions of lead (Pb) ions at the Large Hadron Collider (LHC) and Future Circular Collider (FCC), using the large (quasi)real photon fluxes available in ultraperipheral collisions. The $\gamma \gamma \to \gamma \gamma$ cross sections for diphoton masses m${}_{\gamma \gamma }>$ 5 GeV in pp, pPb, and PbPb collisions at LHC ($\sqrt{{\mathrm{s}}_{{}_{\mathrm{NN}}}}$ = 5.5, 8.8, 14 TeV) and FCC ($\sqrt{{\mathrm{s}}_{{}_{\mathrm{NN}}}}$ = 39, 63, 100 TeV) center-of-mass energies are presented. The measurement has controllable backgrounds in PbPb collisions, and one expects about 70 and 2500 signal events per year at the LHC and FCC respectively, after typical detector acceptance and reconstruction efficiency selections.

   hep-phhep-exnucl-exnucl-th6 citations
6. 06*

   A flavour physics scenario for the 750 GeV diphoton anomaly

   Cesar Bonilla🇪🇸 · Miguel Nebot🇪🇸 · Rahul Srivastava🇮🇳 · Jose W.F. Valle🇪🇸

   A simple variant of a realistic flavour symmetry scheme for fermion masses and mixings provides a possible interpretation of the diphoton anomaly as an electroweak singlet "flavon". The existence of TeV scale vector-like T-quarks required to provide adequate values for CKM parameters can also naturally account for the diphoton anomaly. Correlations between $V_{ub}$ and $V_{cb}$ with the vector-like T-quark mass can be predicted. Should the diphoton anomaly survive in a future Run, our proposed interpretation can also be tested in upcoming B and LHC studies.

   hep-phPRD(2016)·19 citations
7. 07*

   Heavy Fermion Bound States for Diphoton Excess at 750GeV $\sim$ Collider and Cosmological Constraints $\sim$

   Chengcheng Han🇯🇵 · Koji Ichikawa🇯🇵 · Shigeki Matsumoto🇯🇵 · Mihoko M. Nojiri🇯🇵 · Michihisa Takeuchi🇯🇵

   A colored heavy particle with sufficiently small width may form non-relativistic bound states when they are produced at the large hadron collider\,(LHC), and they can annihilate into a diphoton final state. The invariant mass of the diphoton would be around twice of the colored particle mass. In this paper, we study if such bound state can be responsible for the 750 GeV diphoton excess reported by ATLAS and CMS. We found that the best-fit signal cross section is obtained for the SU(2)${}_L$ singlet colored fermion $X$ with $Y_X=4/3$. Having such an exotic hypercharge, the particle is expected to decay through some higher dimensional operators, consistent with the small width assumption. The decay of $X$ may involve a stable particle $\chi$, if both $X$ and $\chi$ are odd under some conserved $Z_2$ symmetry. In that case, the particle $X$ suffers from the constraints of jets + missing $E_T$ searches by ATLAS and CMS at 8 TeV and 13 TeV. We found that such a scenario still survives if the mass difference between $X$ and $\chi$ is above $\sim$ 30 GeV for $m_X\sim 375$ GeV. Even assuming pair annihilation of $\chi$ is small, the relic density of $\chi$ is small enough if the mass difference between $X$ and $\chi$ is smaller than $\sim$ 40 GeV.

   hep-phhep-exJHEP(2016)·29 citations
8. 08*

   Theoretical uncertainty of the supersymmetric dark matter relic density from scheme and scale variations

   J. Harz🇫🇷 · B. Herrmann🇫🇷 · M. Klasen🇩🇪 · K. Kovarik🇩🇪 · P. Steppeler🇩🇪

   For particle physics observables at colliders such as the LHC at CERN, it has been common practice for many decades to estimate the theoretical uncertainty by studying the variations of the predicted cross sections with a priori unpredictable scales. In astroparticle physics, this has so far not been possible, since most of the observables were calculated at Born level only, so that the renormalization scheme and scale dependence could not be studied in a meaningful way. In this paper, we present the first quantitative study of the theoretical uncertainty of the neutralino dark matter relic density from scheme and scale variations. We first explain in detail how the renormalization scale enters the tree-level calculations through coupling constants, masses and mixing angles. We then demonstrate a reduction of the renormalization scale dependence through one-loop SUSY-QCD corrections in many different dark matter annihilation channels and enhanced perturbative stability of a mixed on-shell/$\overline{\mathrm{DR}}$ renormalization scheme over a pure $\overline{\mathrm{DR}}$ scheme in the top-quark sector. In the stop-stop annihilation channel, the Sommerfeld enhancement and its scale dependence are shown to be of particular importance. Finally, the impact of our higher-order SUSY-QCD corrections and their scale uncertainties are studied in three typical scenarios of the phenomenological Minimal Supersymmetric Standard Model with eleven parameters (pMSSM-11). We find that the theoretical uncertainty is reduced in many cases and can become comparable to the size of the experimental one in some scenarios.

   hep-phastro-ph.COhep-exPRD(2016)·51 citations
9. 09*

   Rapid thermal co-annihilation through bound states in QCD

   Seyong Kim🇰🇷 · M. Laine🇨🇭

   The co-annihilation rate of heavy particles close to thermal equilibrium, which plays a role in many classic dark matter scenarios, can be "simulated" in QCD by considering the pair annihilation rate of a heavy quark and antiquark at a temperature of a few hundred MeV. We show that the so-called Sommerfeld factors, parameterizing the rate, can be defined and measured non-perturbatively within the NRQCD framework. Lattice measurements indicate a modest suppression in the octet channel, in reasonable agreement with perturbation theory, and a large enhancement in the singlet channel, much above the perturbative prediction. The additional enhancement is suggested to originate from bound state formation and subsequent decay. Making use of a Green's function based method to incorporate thermal corrections in perturbative co-annihilation rate computations, we show that qualitative agreement with lattice data can be found once thermally broadened bound states are accounted for. We suggest that our formalism may also be applicable to specific dark matter models which have complicated bound state structures.

   hep-phhep-latJHEP(2016)·43 citations
10. 10*

    Constraints on $Z^{\prime }$ Boson within Minimal Flavor Violation

    C.S. Kim🇰🇷 · Xing-Bo Yuan🇰🇷 · Ya-Juan Zheng🇰🇷

    We explore a $Z^{\prime }$ boson coupled only with the Standard Model (SM) fermions ($Z^{\prime }f\bar{f}$) in the framework of Minimal Flavor Violation. We study its effects on the processes with lepton flavor violation ${\ell }_j\to {\ell }_i{\ell }_k{\bar{\ell }}_l$, ${\ell }_j\to {\ell }_i\gamma$, ${\mu }^{-}N\to e^{-}N$, quark flavor changing neutral currents $b\to s{\ell }^{+}{\ell }^{-}$, neutral $B$ and $K$ meson mixing, and $e^{+}{e}^{-}\to f\bar{f}$ at the LEP experiment to constrain the parameter space of $Z^{\prime }$ mass and couplings. We find that among those relevant processes, $\mu \to e\gamma$, $\mu \to 3e$, $\mu$-$e$ conversion and $e^{+}{e}^{-}\to f\bar{f}$ can put more stringent bounds on $Z^{\prime }f\bar{f}$ couplings normalized by $Z^{\prime }$ mass. Its implications on various processes are obtained, such as $B$ and $K$ mixing and $B/K\to M{\ell }_1{\bar{\ell }}_2$ decays. In addition, we also make analysis on $Z^{\prime }$ signatures at the LHC with $\sqrt{s}=8$ and 13 TeV.

    hep-phPRD(2016)·24 citations
11. 11*

    Realizing the supersymmetric inverse seesaw model in the framework of R-parity violation

    C. A. de S. Pires🇧🇷 · J. G. Rodrigues🇧🇷 · P. S. Rodrigues da Silva🇧🇷

    If, on one hand, the inverse seesaw is the paradigm of TeV scale seesaw mechanism, on the other it is a challenge to find scenarios capable of realizing it. In this work we propose a scenario, based on the framework of R-parity violation, that realizes minimally the supersymmetric inverse seesaw mechanism. In it the energy scale parameters involved in the mechanism are recognized as the vacuum expectation values of the scalars that compose the singlet superfields ${\hat{N}}^C$ and $\hat{S}$. We develop also the scalar sector of the model and show that the Higgs mass receives a new tree-level contribution that, when combined with the standard contribution plus loop correction, is capable of attaining $125$GeV without resort to heavy stops.

    hep-phPLB(2016)·2 citations
12. 12*

    Resummation of High Order Corrections in Higgs Boson Plus Jet Production at the LHC

    Peng Sun🇺🇸 · Joshua Isaacson🇺🇸 · C.-P. Yuan🇺🇸 · Feng Yuan🇺🇸

    We study the effect of multiple parton radiation to Higgs boson plus jet production at the LHC, by applying the transverse momentum dependent (TMD) factorization formalism to resum large logarithmic contributions to all orders in the expansion of the strong interaction coupling. We show that the appropriate resummation scale should be the jet transverse momentum, rather than the partonic center of mass energy which has been normally used in the TMD resummation formalism. Furthermore, the transverse momentum distribution of the Higgs boson, particularly near the lower cut-off applied on the jet transverse momentum, can only be reliably predicted by the resummation calculation which is free of the so-called Sudakov-shoulder singularity problem, present in fixed-order calculations.

    hep-phPLB(2017)·24 citations
13. 13*

    Phenomenology of the Z-boson plus jet process at NNLO

    Radja Boughezal🇺🇸 · Xiaohui Liu🇺🇸 · Frank Petriello🇺🇸

    We present a detailed phenomenological study of Z-boson production in association with a jet through next-to-next-to-leading order (NNLO) in perturbative QCD. Fiducial cross sections and differential distributions for both 8 TeV and 13 TeV LHC collisions are presented. We study the impact of different parton distribution functions (PDFs) on predictions for the Z+jet process. Upon inclusion of the NNLO corrections, the residual scale uncertainty is reduced such that both the total rate and the transverse momentum distributions can be used to discriminate between various PDF sets.

    hep-phPRD(2016)·85 citations
14. 14*

    Symmetry breaking patterns of the 3-3-1 model at finite temperature

    J. Sá Borges🇧🇷 · Rudnei O. Ramos🇧🇷

    We consider the minimal version of an extension of the standard electroweak model based on the $SU(3{)}_c\times SU(3{)}_L\times U(1{)}_X$ gauge symmetry (the 3-3-1 model). We analyze the most general potential constructed from three scalars in the triplet representation of $SU(3{)}_L$, whose neutral components develop nonzero vacuum expectation values, giving mass for all the model's massive particles. {}For different choices of parameters, we obtain the particle spectrum for the two symmetry breaking scales: one where the $SU(3{)}_L\times U(1{)}_X$ group is broken down to $SU(2{)}_L\times U(1{)}_Y$ and a lower scale similar to the standard model one. Within the considerations used, we show that the model encodes two first-order phase transitions, respecting the pattern of symmetry restoration. The last transition, corresponding to the standard electroweak one, is found to be very weak first-order, most likely turning second-order or a crossover in practice. However, the first transition in this model can be strongly first-order, which might happen at a temperature not too high above the second one. We determine the respective critical temperatures for symmetry restoration for the model.

    hep-phEPJC(2016)·25 citations
15. 15*

    Charged Fermion Masses and Mixing from a SU(3) Family Symmetry Model

    Albino Hernandez-Galeana🇲🇽

    Within the framework of a Beyond Standard Model (BSM) with a local $SU(3)$ family symmetry, we report an updated fit of parameters which account for the known spectrum of quarks and charged lepton masses and the quark mixing in a $4\times 4$ non-unitary $V_{CKM}$. In this scenario, ordinary heavy fermions, top and bottom quarks and tau lepton, become massive at tree level from Dirac See-saw mechanisms implemented by the introduction of a new set of $SU(2{)}_L$ weak singlet vector-like fermions, $U,D,E,N$, with $N$ a sterile neutrino. The $N_{L,R}$ sterile neutrinos allow the implementation of a $8\times 8$ general See-saw Majorana neutrino mass matrix with four massless eigenvalues at tree level. Hence, light fermions, including neutrinos, obtain masses from loop radiative corrections mediated by the massive $SU(3)$ gauge bosons. $SU(3)$ family symmetry is broken spontaneously in two stages, whose hierarchy of scales yield an approximate $SU(2)$ global symmetry associated with the $Z_1,Y_1^{\pm }$ gauge boson masses of the order of 2 TeV. A global fit of parameters to include neutrino masses and lepton mixing is in progress.

    hep-phBled Workshops Phys.(2015)·6 citations
16. 16*

    Exact vector channel sum rules at finite temperature and their applications to lattice QCD data analysis

    Philipp Gubler🇮🇹 · Daisuke Satow🇮🇹

    We derive three exact sum rules for the spectral function of the electromagnetic current with zero spatial momentum at finite temperature. Two of them are derived in this paper for the first time. We explicitly check that these sum rules are satisfied in the weak coupling regime and examine which sum rule is sensitive to the transport peak in the spectral function at low energy or the continuum at high energy. Possible applications of the three sum rules to lattice computations of the spectral function and transport coefficients are also discussed: We propose an ansatz for the spectral function that can be applied to all three sum rules and fit it to available lattice data of the Euclidean vector correlator above the critical temperature. As a result, we obtain estimates for both the electrical conductivity $\sigma$ and the second order transport coefficient ${\tau }_J$.

    hep-phhep-latPRD(2016)·9 citations
17. 17*

    On a possibility of a consistent interpretation of diboson excesses at LHC

    B.A. Arbuzov🇷🇺 · I.V. Zaitsev🇷🇺

    Recently reported diboson and diphoton excesses at LHC are interpreted to be connected with heavy $WW$ zero spin resonances. The resonances appears due to the wouldbe anomalous triple interaction of the weak bosons, which is defined by well-known coupling constant $\lambda$. The $2TeV$ anomaly tentatively corresponds to weak isotopic spin 2 scalar state and the $\gamma \gamma 750GeV$ anomaly corresponds to weak isotopic spin 0 pseudoscalar state. We obtain estimates for the effect, which qualitatively agree with ATLAS data. Effects are predicted in a production of $W^{+}{W}^{-},(Z,\gamma )(Z,\gamma )$ via resonance $X_{PS}$ with $M_{PS}\simeq 750GeV$, which could be reliably checked at the upgraded LHC at $\sqrt{s}=13TeV$. In the framework of an approach to the spontaneous generation of the triple anomalous interaction its coupling constant is estimated to be $\lambda =-0.02\pm 0.005$ in an agreement with existing restrictions. Specific predictions of the hypothesis are significant effects in decay channels $X_{PS}\to \gamma l^{+}{l}^{-},X_{PS}\to l^{+}{l}^{-}{l}^{+}{l}^{-}(l=e,\mu )$.

    hep-phhep-exMod.Phys.Lett.A(2016)·4 citations
18. 18*

    Influence on Starobinsky inflation by other fields with large amplitude

    Shinta Kasuya🇯🇵 · Kanto Moritake🇯🇵

    The Starobinsky model is one of the inflation models consistent with the result of CMB observation by the Planck satellite. We consider the dynamics of the Starobinsky inflation in the presence of another scalar field with a large expectation value during inflation due to a negative Hubble-induced mass. We find that it would be affected if the other field has an amplitude close to the Planck scale. In this case, we may observe such effects on the Starobinsky model by future CMB experiments.

    hep-phastro-ph.COPRD(2016)·0 citations
19. 19*

    Radiative Neutrino Mass in Alternative Left-Right Model

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼 · Yuta Orikasa🇰🇷

    We propose a radiative seesaw model in alternative left-right model without any bidoublet scalar fields, in which all the fermion masses in the standard model are generated through a canonical seesaw mechanism at the tree level. On the other hand the observed neutrino masses are generated at two-loop level. In this paper we focus on the neutrino sector and show how to induce the active neutrino masses. Then we discuss the observed neutrino oscillation, constraints from lepton flavor violations, new sources of muon anomalous magnetic moment, a long-lived dark matter candidate with keV scale mass, and collider physics.

    hep-phEPJC(2017)·34 citations
20. 20*

    Low-dimensional approach to pair production in an oscillating electric field: Application to bandgap graphene layers

    Ibrahim Akal🇩🇪 · Reinhold Egger🇩🇪 · Carsten Müller🇩🇪 · Selym Villalba-Chávez🇩🇪

    The production of particle-antiparticle pairs from the quantum field theoretic ground state in the presence of an external electric field is studied. Starting with the quantum kinetic Boltzmann-Vlasov equation in four-dimensional spacetime, we obtain the corresponding equations in lower dimensionalities by way of spatial compactification. Our outcomes in $2+1$-dimensions are applied to bandgap graphene layers, where the charge carriers have the particular property of behaving like light massive Dirac fermions. We calculate the single-particle distribution function for the case of an electric field oscillating in time and show that the creation of particle-hole pairs in this condensed matter system closely resembles electron-positron pair production by the Schwinger effect.

    hep-phcond-mat.mes-hallPRD(2016)·30 citations
21. 21*

    The BSM Physics Case of the ILC

    Jürgen Reuter🇩🇪

    In this talk I summarize the physics case of the International Linear Collider (ILC) focusing on its potential towards discovery, discrimation or disentanglement of new physics beyond the Standard Model (BSM).

    hep-phhep-ex4 citations
22. 22*

    Erratum for the time-like evolution in QCDNUM

    M. Botje🇳🇱

    A recent comparison of the evolution programs QCDNUM and APFEL showed a discrepancy in the time-like evolution of the singlet fragmentation function at NLO. It was found that the splitting functions of this evolution were wrongly assigned in QCDNUM, and also that the fragmentation functions were not correctly matched at the flavour thresholds. These errors are corrected in a new release of the program.

    hep-ph14 citations
23. 23*

    The pion-kaon scattering amplitude constrained with forward dispersion relations up to 1.6 GeV

    J. R. Pelaez🇪🇸 · A. Rodas (Universidad Complutense de Madrid)🇪🇸

    In this work we provide simple and precise parameterizations of the existing $\pi K$ scattering data from threshold up to 1.6 GeV, which are constrained to satisfy forward dispersion relations as well as three additional threshold sum rules. We also provide phenomenological values of the threshold parameters and of the resonance poles that appear in elastic scattering.

    hep-phPRD(2016)·69 citations
24. 24*

    ${\chi }_{c0}^{}(3915)$ As the Lightest $c\bar{c}s\bar{s}$ State

    Richard F. Lebed🇺🇸 · Antonio D. Polosa🇮🇹

    The state ${\chi }_{c0}^{}(3915)$ has recently been demoted by the Particle Data Group from its previous status as the conventional $c\bar{c}$ $2{}^3{P}_0$ state, largely due to the absence of expected $D\bar{D}$ decays. We propose that ${\chi }_{c0}^{}(3915)$ is actually the lightest $c\bar{c}s\bar{s}$ state, and calculate the spectrum of such states using the diquark model, identifying many of the observed charmoniumlike states that lack open-charm decay modes as $c\bar{c}s\bar{s}$. Among other results, we argue that $Y(4140)$ is a $J^{PC}=1^{++}$ $c\bar{c}s\bar{s}$ state that has been not been seen in two-photon fusion largely as a consequence of the Landau-Yang theorem.

    hep-phnucl-thPRD(2016)·97 citations
25. 25*

    Thermodynamics of the $d$=3+1 Quantum XY Model

    Christoph P. Hofmann🇲🇽

    Within effective field theory we explore the properties of the $d$=3+1 quantum XY model at low temperatures and in weak magnetic or staggered fields. For this parameter regime only few results appear to be known, and furthermore are restricted to one-loop order. In the present study we systematically analyze the thermodynamics of the $d$=3+1 quantum XY model up to three-loop order. In the low-temperature expansion of the free energy density, the free Bose gas term of order $T^4$ receives corrections of order $T^6$ and $T^8$. The discussion also includes the pressure, (staggered) magnetization and susceptibility. In particular, we show how these quantities are influenced by the spin-wave interaction. We then compare our findings with those for the quantum XY model in $d$=2+1.

    ↳ cond-mat.str-elhep-lathep-phJ.Stat.Mech.(2016)·3 citations
26. 26*

    Dark matter component decaying after recombination: lensing constraints with Planck data

    A. Chudaykin🇷🇺 · D. Gorbunov🇷🇺 · I. Tkachev🇷🇺

    It has been recently suggested~\cite{Berezhiani:2015yta} that emerging tension between cosmological parameter values derived in high-redshift (CMB anisotropy) and low-redshift (cluster counts, Hubble constant) measurements can be reconciled in a model which contains subdominant fraction of dark matter decaying after recombination. We check the model against the CMB Planck data. We find that lensing of the CMB anisotropies by the large-scale structure gives strong extra constraints on this model, limiting the fraction as $F<8\%$ at 2\,$\sigma$ confidence level. However, investigating the combined data set of CMB and conflicting low-$z$ measurements, we obtain that the model with $F\approx 2-5$\% exhibits better fit (by 1.5-3\,$\sigma$ depending on the lensing priors) compared to that of the concordance $\Lambda$CDM cosmological model.

    ↳ astro-ph.COhep-phPRD(2016)·70 citations
27. 27*

    Holographic Curvature Perturbations in a Cosmology with a Space-Like Singularity

    Elisa G. M. Ferreira🇨🇦 · Robert Brandenberger🇨🇦

    We study the evolution of cosmological perturbations in an anti-de-Sitter (AdS) bulk through a cosmological singularity by mapping the dynamics onto the boundary conformal fields theory by means of the AdS/CFT correspondence. We consider a deformed AdS space-time obtained by considering a time-dependent dilaton which induces a curvature singularity in the bulk at a time which we call $t=0$, and which asymptotically approaches AdS both for large positive and negative times. The boundary field theory becomes free when the bulk curvature goes to infinity. Hence, the evolution of the fluctuations is under better controle on the boundary than in the bulk. To avoid unbounded particle production across the bounce it is necessary to smooth out the curvature singularity at very high curvatures. We show how the bulk cosmological perturbations can be mapped onto boundary gauge field fluctuations. We evolve the latter and compare the spectrum of fluctuations on the infrared scales relevant for cosmological observations before and after the bounce point. We find that the index of the power spectrum of fluctuations is the same before and after the bounce.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2016)·14 citations
28. 28*

    BCS, Nambu-Jona-Lasinio, and Han-Nambu -- A sketch of Nambu's works in 1960-1965

    Kazuo Fujikawa🇯🇵

    The years of 1960-1965 were a remarkable period for Yoichiro Nambu. Starting with a reformulation of BCS theory with emphasis on gauge invariance, he recognized the realization of spontaneous chiral symmetry breaking in particle physics as is evidenced by the Goldberger-Treiman relation. A concrete model of Nambu and Jona-Lasinio illustrated the essence of the Nambu-Goldstone theorem and the idea of soft pions. After the proposal of the quark model by Gell-Mann, he together with Han constructed an alternative model of integrally charged quarks with possible non-Abelian gluons. All those remarkable works were performed during the years 1960-1965. Here I briefly review those works following the original papers of Nambu chronologically, together with a brief introduction to a formulation of Neother's theorem and Ward-Takahashi identities using path integrals. This article is mostly based on a lecture given at the Nambu Memorial Symposium held at Osaka City University in September 2015, where Nambu started his professional career.

    ↳ physics.hist-phhep-phhep-thPTEP(2016)·2 citations
29. 29*

    Generation of random deviates for relativistic quantum-statistical distributions

    Boris Tomášik🇸🇰 · Ivan Melo🇸🇰 · Jakub Cimerman🇨🇿

    We provide an algorithm for generation of momenta (or energies) of relativistic particles according to the relativistic Bose-Einstein or Fermi-Dirac distributions. The algorithm uses rejection method with effectively selected comparison function so that the acceptance rate of the generated values is always better than 0.9. It might find its use in Monte-Carlo generators of particles from reactions in high-energy physics.

    ↳ physics.comp-phhep-phnucl-th0 citations
30. 30*

    Mass inflation in Eddington-inspired Born-Infeld black holes: analytical scaling solutions

    P. P. Avelino🇵🇹

    We study the inner dynamics of accreting Eddington-inspired Born-Infeld black holes using the homogeneous approximation and taking charge as a surrogate for angular momentum. We show that there is a minimum of the accretion rate below which mass inflation does not occur, and we derive an analytical expression for this threshold as a function of the fundamental scale of the theory, the accretion rate, the mass, and the charge of the black hole. Our result explicitly demonstrates that, no matter how close Eddington-inspired Born-Infeld gravity is to general relativity, there is always a minimum accretion rate below which there is no mass inflation. For larger accretion rates, mass inflation takes place inside the black hole as in general relativity until the extremely rapid density variations bring it to an abrupt end. We derive analytical scaling solutions for the value of the energy density and of the Misner-Sharp mass attained at the end of mass inflation as a function of fundamental scale of the theory, the accretion rate, the mass, and the charge of the black hole, and compare these with the corresponding numerical solutions. We find that, except for unreasonably high accretion rates, our analytical results appear to provide an accurate description of homogeneous mass inflation inside accreting Eddington-inspired Born-Infeld black holes.

    ↳ gr-qcastro-ph.COastro-ph.HEhep-ph+1PRD(2016)·21 citations
31. 31*

    Constraints on modified gravity from Planck 2015: when the health of your theory makes the difference

    Valentina Salvatelli🇮🇹 · Federico Piazza🇫🇷 · Christian Marinoni🇫🇷

    We use the effective field theory of dark energy (EFT of DE) formalism to constrain dark energy models belonging to the Horndeski class with the recent Planck 2015 CMB data. The space of theories is spanned by a certain number of parameters determining the linear cosmological perturbations, while the expansion history is set to that of a standard $\Lambda$CDM model. We always demand that the theories be free of fatal instabilities. Additionally, we consider two optional conditions, namely that scalar and tensor perturbations propagate with subliminal speed. Such criteria severely restrict the allowed parameter space and are thus very effective in shaping the posteriors. As a result, we confirm that no theory performs better than $\Lambda$CDM when CMB data alone are analysed. Indeed, the healthy dark energy models considered here are not able to reproduce those phenomenological behaviours of the effective Newton constant and gravitational slip parameters that, according to previous studies, best fit the data.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2016)·67 citations
32. 32*

    Thermodynamics and kinetics of Gribov-Zwanziger plasma with temperature dependent Gribov parameter

    Viktor Begun🇵🇱 · Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱

    A Gribov-type dispersion relation is treated as an effective description of interacting gluons forming a hot medium. Temperature dependence of the Gribov parameter is determined from the fit to the lattice Yang-Mills results describing thermodynamic functions. To maintain thermodynamic consistency of the approach, a temperature dependent bag pressure is introduced. The results obtained for equilibrium functions are generalised in the next step to non-equilibrium conditions. We derive formulas for the bulk and shear viscosity coefficients within the relaxation time approximation. We find evidence for largely enhanced bulk viscosity in the region of the phase transition.

    ↳ nucl-thhep-phActa Phys.Polon.B(2017)·13 citations
33. 33*

    Modified Magnetohydrodynamics Around the Electroweak Transition

    Petar Pavlović🇩🇪 · Natacha Leite🇩🇪 · Günter Sigl🇩🇪

    We analyse solutions of the MHD equations around the electroweak transition taking into account the effects of the chiral anomaly. It is shown that a transition that is not of the first order has direct consequences on the evolution of the asymmetry between left- and right-handed leptons. Assuming an initial chiral asymmetry in the symmetric phase at temperatures higher than the transition temperature, as well as the existence of magnetic fields, it is demonstrated that the asymmetry typically grows with time, until it undergoes a fast decrease at the transition, and then eventually gets damped at lower temperatures in the broken phase. We argue that it is unlikely to have any significant magnetic field amplification as a consequence of the electroweak transition in the Standard model, even when the chiral anomaly is introduced. The presence of a chiral asymmetry between left- and right-handed charge carriers naturally leads to the creation of helical magnetic fields from non-helical fields and this can have consequences on their subsequent evolution.

    ↳ astro-ph.COhep-phJCAP(2016)·22 citations
34. 34*

    Neutrino footprint in Large Scale Structure

    Raul Jimenez🇪🇸 · Carlos Pena-Garay🇪🇸 · Licia Verde🇪🇸

    Recent constrains on the sum of neutrino masses inferred by analyzing cosmological data, show that detecting a non-zero neutrino mass is within reach of forthcoming cosmological surveys, implying a direct determination of the absolute neutrino mass scale. The measurement relies on constraining the shape of the matter power spectrum below the neutrino free streaming scale: massive neutrinos erase power at these scales. Detection of a lack of small-scale power, however, could also be due to a host of other effects. It is therefore of paramount importance to validate neutrinos as the source of power suppression at small scales. We show that, independent on hierarchy, neutrinos always show a footprint on large, linear scales; the exact location and properties can be related to the measured power suppression (an astrophysical measurement) and atmospheric neutrinos mass splitting (a neutrino oscillation experiment measurement). This feature can not be easily mimicked by systematic uncertainties or modifications in the cosmological model. The measurement of such a feature, up to 1% relative change in the power spectrum, is a smoking gun for confirming the determination of the absolute neutrino mass scale from cosmological observations. It also demonstrates the synergy of astrophysics and particle physics experiments.

    ↳ astro-ph.COhep-phPhys.Dark Univ.(2017)·20 citations
35. 35*

    Reionization during the dark ages from a cosmic axion background

    Carmelo Evoli🇮🇹 · Matteo Leo🇬🇧 · Alessandro Mirizzi🇮🇹 · Daniele Montanino🇮🇹

    Recently it has been pointed out that a cosmic background of relativistic axion-like particles (ALPs) would be produced by the primordial decays of heavy fields in the post-inflation epoch, contributing to the extra-radiation content in the Universe today. Primordial magnetic fields would trigger conversions of these ALPs into sub-MeV photons during the dark ages. This photon flux would produce an early reionization of the Universe, leaving a significant imprint on the total optical depth to recombination $\tau$. Using the current measurement of $\tau$ and the limit on the extra-radiation content $\Delta N_{\mathrm{eff}}$ by the Planck experiment we put a strong bound on the ALP-photon conversions. Namely we obtain upper limits on the product of the photon-ALP coupling constant $g_{a\gamma }$ times the magnetic field strength $B$ down to $g_{a\gamma }B\gtrsim 6\times 10^{-18}{\text{GeV}}^{-1}\text{nG}$ for ultralight ALPs.

    ↳ astro-ph.COastro-ph.HEhep-phJCAP(2016)·22 citations
36. 36*

    High Energy Neutrinos from the Gravitational Wave event GW150914 possibly associated with a short Gamma-Ray Burst

    Reetanjali Moharana🇿🇦 · Soebur Razzaque🇿🇦 · Nayantara Gupta🇮🇳 · Peter Meszaros🇺🇸

    High-energy neutrino (HEN) and gravitational wave (GW) can probe astrophysical sources in addition to electromagnetic observations. Multimessenger studies can reveal nature of the sources which may not be discerned from one type of signal alone. We discuss HEN emission in connection with the Advanced Laser Interferometer Gravitational-wave Observatory (ALIGO) event GW150914 which could be associated with a short gamma-ray burst (GRB) detected by the $Fermi$ Gamma-ray Burst Monitor (GBM) 0.4 s after the GW event and within localization uncertainty of the GW event. We calculate HEN flux from this short GRB, GW150914-GBM, and show that non-detection of a high-energy starting event (HESE) by the IceCube Neutrino Observatory can constrain the total isotropic-equivalent jet energy of this short burst to be less than $3\times 10^{52}$ erg.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2016)·20 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.