Thu·May 4, 2017Thursday·May 4, 2017

1. 01*

   Seeking the CP-odd Higgs via $h\to {\eta }_{c,b}{\ell }^{+}{\ell }^{-}$

   Damir Bečirević🇫🇷 · Blaženka Melić🇭🇷 · Monalisa Patra🇭🇷 · Olcyr Sumensari🇫🇷

   We show that the decay rates of the Higgs boson to a pseudoscalar quarkonium and a pair of leptons, $h\to P{\ell }^{+}{\ell }^{-}$ ($P\in \{{\eta }_c,{\eta }_b\}$), can be substantially enhanced in a scenario with two Higgs doublets with a softly broken ${\mathbb{Z}}_2$ symmetry (2HDM) when the CP-odd Higgs A is light, i.e. $m_A\lesssim m_h$. Depending on the type of 2HDM the enhancement of $\mathcal{B}(h\to {\eta }_{c,b}{\tau }^{+}{\tau }^{-})$ with respect to its Standard Model value can be an order of magnitude larger, i.e. $\mathcal{O}(10^{-6}÷10^{-5})$. The decays $h\to P{\ell }^{+}{\ell }^{-}$ could therefore provide an efficient channel to investigate the presence of a light CP-odd Higgs $A$ and help to disentangle among various 2HDM scenarios.

   hep-phPRD(2018)·11 citations
2. 02*

   Neutrino Mass Generation at TeV Scale and New Physics Signatures from Charged Higgs at the LHC for Photon Initiated Processes

   Kirtiman Ghosh🇮🇳 · Sudip Jana🇺🇸 · S. Nandi🇺🇸

   We consider the collider phenomenology of a simple extension of the Standard Model (SM), which consists of an EW isospin $3/2$ scalar, $\Delta$ and a pair of EW isospin $1$ vector like fermions, $\Sigma$ and $\bar{\Sigma }$, responsible for generating tiny neutrino mass via the effective dimension seven operator. This scalar quadruplet with hypercharge Y = 3 has a plethora of implications at the collider experiments. Its signatures at TeV scale colliders are expected to be seen, if the quadruplet masses are not too far above the electroweak symmetry breaking scale. In this article, we study the phenomenology of multi-charged quadruplet scalars. In particular, we study the multi-lepton signatures at the Large Hadron Collider (LHC) experiment, arising from the production and decays of triply and doubly charged scalars. We studied Drell-Yan (DY) pair production as well as pair production of the charged scalars via photon-photon fusion. For doubly and triply charged scalars, photon fusion contributes significantly for large scalar masses. We also studied LHC constraints on the masses of doubly charged scalars in this model. We derive a lower mass limit of 725 GeV on doubly charged quadruplet scalar.

   hep-phhep-exJHEP(2018)·30 citations
3. 03*

   Prospects for axion detection in natural SUSY with mixed axion-higgsino dark matter: back to invisible?

   Kyu Jung Bae🇰🇷 · Howard Baer🇺🇸 · Hasan Serce🇺🇸

   Under the expectation that nature is natural, we extend the Standard Model to include SUSY to stabilize the electroweak sector and PQ symmetry to stabilize the QCD sector. Then natural SUSY arises from a Kim-Nilles solution to the SUSY mu problem which allows for a little hierarchy where mu ~ f_a^2/M_P ~ 100-300 GeV while the SUSY particle mass scale m(SUSY)~ 1-10 TeV >> mu. Dark matter then consists of two particles: a higgsino-like WIMP and a SUSY DFSZ axion. The range of allowed axion mass values m(axion) depends on the mixed axion-higgsino relic density. The range of m(axion) is actually restricted in this case by limits on WIMPs from direct and indirect detection experiments. We plot the expected axion detection rate at microwave cavity experiments. The axion-photon-photon coupling is severely diminished by charged higgsino contributions to the anomalous coupling. In this case, the axion may retreat, at least temporarily, back into the regime of near invisibility. From our results, we urge new ideas for techniques which probe both deeper and more broadly into axion coupling versus axion mass parameter space.

   hep-phastro-ph.COJCAP(2017)·48 citations
4. 04*

   Light-by-light forward scattering sum rules for charmonium states

   Igor Danilkin🇩🇪 · Marc Vanderhaeghen🇩🇪

   We apply three forward light-by-light scattering sum rules to charmonium states. We show that these sum rules imply a cancellation between charmonium bound state contributions, which are mostly known from the $\gamma \gamma$ decay widths of these states, and continuum contributions above $D\bar{D}$ threshold, for which we provide a duality estimate. We also show that two of these sum rules allow to predict the yet unmeasured ${\gamma }^{\ast }\gamma$ coupling of the ${\chi }_{c1}(1P)$ state, which can be tested at present high-luminosity $e^{+}{e}^{-}$ colliders.

   hep-phPRD(2017)·5 citations
5. 05*

   Probe CP violation in $H\to \gamma Z$ through forward-backward asymmetry

   Xuan Chen🇨🇳 · Gang Li🇨🇳 · Xia Wan🇨🇳

   We suggest that the forward-backward asymmetry $(A_{FB})$ of the charged leptons in $gg\to H\to \gamma Z\to \gamma {\ell }^{-}{\ell }^{+}$ process could be used to probe the CP violating $H\gamma Z$ coupling when the interference from $gg\to \gamma Z\to \gamma {\ell }^{-}{\ell }^{+}$ process is included. With CP violation in $H\gamma Z$ coupling, the interference effect leads to a non-vanishing $A_{FB}$, which is also sensitive to the strong phase differences. The resonant and non-resonant strong phases together make $A_{FB}(\hat{s})$ change sign around Higgs mass $M_H$. For phenomenology study, we suggest the integral over one-side mass region below $M_H$ to magnify the $A_{FB}$ strength.

   hep-phPRD(2017)·14 citations
6. 06*

   Implications of the latest NO$\nu$A results

   Srubabati Goswami🇮🇳 · Newton Nath🇮🇳

   We discuss the implications of the latest NO$\nu$A results on the measurement of ${\nu }_{\mu }-{\nu }_e$ conversions. From a combined analysis of the disappearance and appearance data, the preferred solutions reported by NO$\nu$A are normal hierarchy (NH) with two degenerate best-fit points one in the lower octant (LO) and ${\delta }_{CP}=1.48\pi$ whereas the other in the higher octant (HO) with ${\delta }_{CP}=0.74\pi$. There is also another solution with inverted hierarchy (IH) which is $0.46\sigma$ away from the best-fit. We discuss and quantify the possibility of resolving these degeneracies by inclusion of NO$\nu$A antineutrino runs. We show that if the true solution corresponds to (NH, LO, $\sim 1.48\pi$) then future data from NO$\nu$A comprising of 3 years of neutrino and 3 years of antineutrino run will be able to resolve the degenerate solutions at 95.45\% C.L. However, if the true solution corresponds to (NH, HO, $\sim 0.74\pi$), a wrong hierarchy-wrong ${\delta }_{CP}$ solution remains unresolved even at 68\% C.L. with the full $3\nu +3\bar{\nu }$ projected run of NO$\nu$A. Same is the case if the IH solution turns out to be the true solution. We further show that DUNE (10 kton) will be able to resolve these degenerate solutions at 99.73\% C.L. with only 1 year of neutrino and one year of antineutrino run [1+1] while 5+5 years of DUNE data can resolve the degeneracies at 99.99\% C.L.

   hep-ph8 citations
7. 07*

   A Bayesian Framework to Constrain the Photon Mass with a Catalog of Fast Radio Bursts

   Lijing Shao🇩🇪 · Bing Zhang🇺🇸

   A hypothetical photon mass, $m_{\gamma }$, gives an energy-dependent light speed in a Lorentz-invariant theory. Such a modification causes an additional time delay between photons of different energies when they travel through a fixed distance. Fast radio bursts (FRBs), with their short time duration and cosmological propagation distance, are excellent astrophysical objects to constrain $m_{\gamma }$. Here for the first time we develop a Bayesian framework to study this problem with a catalog of FRBs. Those FRBs with and without redshift measurement are both useful in this framework, and can be combined in a Bayesian way. A catalog of 21 FRBs (including 20 FRBs without redshift measurement, and one, FRB 121102, with a measured redshift $z=0.19273\pm 0.00008$) give a combined limit $m_{\gamma }\le 8.7\times 10^{-51}\mathrm{kg}$, or equivalently $m_{\gamma }\le 4.9\times 10^{-15}\mathrm{eV}/c^2$ ($m_{\gamma }\le 1.5\times 10^{-50}\mathrm{kg}$, or equivalently $m_{\gamma }\le 8.4\times 10^{-15}\mathrm{eV}/c^2$) at 68% (95%) confidence level, which represents the best limit that comes purely from kinematics. The framework proposed here will be valuable when FRBs are observed daily in the future. Increment in the number of FRBs, and refinement in the knowledge about the electron distributions in the Milky Way, the host galaxies of FRBs, and the intergalactic median, will further tighten the constraint.

   hep-phastro-ph.COastro-ph.HEgr-qcPRD(2017)·57 citations
8. 08*

   The breaking of flavor democracy in the quark sector

   Harald Fritzsch🇩🇪 · Zhi-zhong Xing🇨🇳 · Di Zhang🇨🇳

   The democracy of quark flavors is a well-motivated flavor symmetry, but it must be properly broken in order to explain the observed quark mass spectrum and flavor mixing pattern. We reconstruct the texture of flavor democracy breaking and evaluate its strength in a novel way, by assuming a parallelism between the Q=+2/3 and Q=-1/3 quark sectors and using a nontrivial parametrization of the flavor mixing matrix. Some phenomenological implications of such democratic quark mass matrices, including their variations in the hierarchy basis and their evolution from the electroweak scale to a superhigh-energy scale, are also discussed.

   hep-phCPC(2017)·15 citations
9. 09*

   Heavy and Strange Holographic Baryons

   Yizhuang Liu🇺🇸 · Ismail Zahed🇺🇸

   We extend the $D4$-$D8$ holographic construction to include three chiral and one heavy flavor, to describe heavy-light baryons with strangeness and their exotics. At strong coupling, the heavy meson always binds to the bulk instanton in the form of a flavor zero mode in the fundamental representation. We quantize the ensuing bound states using the collective quantization method, to obtain the spectra of heavy and strange baryons with both explicit and hidden charm and bottom. Our results confirm the existence of two low-lying charmed penta-quark states with ${\frac{1}{2}}^{-},{\frac{3}{2}}^{-}$ assignments, and predict many new ones with both charm and bottom. They also suggest a quartet of low-lying neutral ${\Omega }_c^0$ with assignments ${\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm }$ that are heavier than the quintuplet of neutral ${\Omega }_c^0$ recently reported by LHCb.

   hep-phhep-lathep-thnucl-thPRD(2017)·21 citations
10. 10*

    E6 GUT through Effects of Dimension-5 Operators

    Chao-Shang Huang🇨🇳 · Wen-Jun Li🇨🇳 · Xiao-Hong Wu🇨🇳

    In the effective field theory framework, quantum gravity can induce effective dimension-5 operators, which have important impacts on grand unified theories. Interestingly, one of main effects is the modification of the usual gauge coupling unification condition. We investigate the gauge coupling unification in $E_6$ under modified gauge coupling unification condition at scales $M_X$ in the presence of one or more dimension-5 operators. It is shown that nonsupersymmetric models of $E_6$ unification can be obtained and can easily satisfy the constraints from the proton lifetime. For constructing these models, we consider several maximal subgroups $H=SO(10)\times U(1),H=SU(3)\times SU(3)\times SU(3)$, and $H=SU(2)\times SU(6)$ of $E_6$ and the usual breaking chains for a specific maximal subgroup, and derive all of the Clebsch-Gordan coefficients ${\Phi }_{s,z}^{(r)}$ associated with $E_6$ breaking to the Standard Model, which are given in Appendix A.

    hep-phJ.Phys.Comm.(2017)·4 citations
11. 11*

    The inert doublet model in the light of Fermi-LAT gamma-ray data: a global fit analysis

    Benedikt Eiteneuer🇩🇪 · Andreas Goudelis🇫🇷 · Jan Heisig🇩🇪

    We perform a global fit within the inert doublet model taking into account experimental observables from colliders, direct and indirect dark matter searches and theoretical constraints. In particular, we consider recent results from searches for dark matter annihilation-induced gamma-rays in dwarf spheroidal galaxies and relax the assumption that the inert doublet model should account for the entire dark matter in the Universe. We moreover study in how far the model is compatible with a possible dark matter explanation of the so-called Galactic center excess. We find two distinct parameter space regions that are consistent with existing constraints and can simultaneously explain the excess: One with dark matter masses near the Higgs resonance and one around 72 GeV where dark matter annihilates predominantly into pairs of virtual electroweak gauge bosons via the four-vertex arising from the inert doublet's kinetic term. We briefly discuss future prospects to probe these scenarios.

    hep-phastro-ph.HEEPJC(2017)·77 citations
12. 12*

    Muon specific two-Higgs-doublet model

    Tomohiro Abe🇯🇵 · Ryosuke Sato🇮🇱 · Kei Yagyu🇮🇹

    We investigate a new type of a two-Higgs-doublet model as a solution of the muon $g-2$ anomaly. We impose a softly-broken $Z_4$ symmetry to forbid tree level flavor changing neutral currents in a natural way. This $Z_4$ symmetry restricts the structure of Yukawa couplings. As a result, extra Higgs boson couplings to muons are enhanced by a factor of $\tan \beta$, while their couplings to all the other standard model fermions are suppressed by $\cot \beta$. Thanks to this coupling property, we can avoid the constraint from leptonic $\tau$ decays in contrast to the lepton specific two-Higgs-doublet model, which can explain the muon $g-2$ within the 2$\sigma$ level but cannot within the $1\sigma$ level due to this constraint. We find that the model can explain the muon $g-2$ within the 1$\sigma$ level satisfying constraints from perturbative unitarity, vacuum stability, electroweak precision measurements, and current LHC data.

    hep-phJHEP(2017)·44 citations
13. 13*

    Signatures of an $S_3$-Orbifold Higgs Model

    Keith Thrasher🇺🇸

    The lack of new physics at the LHC has sparked renewed interest in theories of neutral naturalness, in which the Standard Model partners required for naturalness carry no Standard Model charge. The Twin Higgs was the first of these theories to be introduced, but recent work has demonstrated it is only an isolated example in a large class of "orbifold Higgs" models. In this work we study an orbifold Higgs model resulting from the orbifold projection by the non-abelian group $S_3$. A model with multiple sectors uncharged under the SM emerges. Constraints are placed on the model from Higgs phenomenology and the prospects of finding evidence at colliders are discussed.

    hep-ph4 citations
14. 14*

    Quasi-PDFs, momentum distributions and pseudo-PDFs

    A. V. Radyushkin🇺🇸

    We show that quasi-PDFs may be treated as hybrids of PDFs and primordial rest-frame momentum distributions of partons. This results in a complicated convolution nature of quasi-PDFs that necessitates using large $p_3\sim 3$ GeV momenta to get reasonably close to the PDF limit. As an alternative approach, we propose to use pseudo-PDFs $P(x,z_3^2)$ that generalize the light-front PDFs onto spacelike intervals and are related to Ioffe-time distributions $M(\nu ,z_3^2)$, the functions of the Ioffe time $\nu =p_3{z}_3$ and the distance parameter $z_3^2$ with respect to which it displays perturbative evolution for small $z_3$. In this form, one may divide out the $z_3^2$ dependence coming from the primordial rest-frame distribution and from the problematic factor due to lattice renormalization of the gauge link. The $\nu$-dependence remains intact and determines the shape of PDFs.

    hep-phhep-latnucl-thPRD(2017)·422 citations
15. 15*

    Loop neutrino masses from d=7 operator

    R. Cepedello🇪🇸 · M. Hirsch🇪🇸 · J.C. Helo🇨🇱

    We discuss the generation of small neutrino masses from d=7 1-loop diagrams. We first systematically analyze all possible d=7 1-loop topologies. There is a total of 48 topologies, but only 8 of these can lead to "genuine" d=7 neutrino masses. Here, we define genuine models to be models in which neither d=5 nor d=7 tree-level masses nor a d=5 1-loop mass appear, such that the d=7 1-loop is the leading order contribution to the neutrino masses. All genuine models can then be organized w.r.t. their particle content. We find there is only one diagram with no representation larger than triplet, while there are 22 diagrams with quadruplets. We briefly discuss three minimal example models of this kind.

    hep-phJHEP(2017)·56 citations
16. 16*

    Leading components in forward elastic hadron scattering: Derivative dispersion relations and asymptotic uniqueness

    D.A. Fagundes🇧🇷 · M.J. Menon🇧🇷 · P.V.R.G. Silva🇧🇷

    Forward amplitude analyses constitute an important approach in the investigation of the energy dependence of the total hadronic cross-section ${\sigma }_{tot}$ and the $\rho$ parameter. The standard picture indicates for ${\sigma }_{tot}$ a leading log-squared dependence at the highest c.m. energies, in accordance with the Froissart-Lukaszuk-Martin bound. Beyond this log-squared (L2) leading dependence, other amplitude analyses have considered a log-raised-to-gamma form (L$\gamma$), with $\gamma$ as a real free fit parameter. In this case, analytic connections with $\rho$ can be obtained either through dispersion relations (derivative forms), or asymptotic uniqueness (Phragmén-Lindelöff theorems). In this work we present a detailed discussion on the similarities and mainly the differences between the Derivative Dispersion Relation (DDR) and Asymptotic Uniqueness (AU) approaches and results, with focus on the L$\gamma$ and L2 leading terms. We also develop new Regge-Gribov fits with updated dataset on ${\sigma }_{tot}$ and $\rho$ from $pp$ and $\bar{p}p$ scattering, in the region 5 GeV-8 TeV. The recent tension between the TOTEM and ATLAS results at 7 TeV and mainly 8 TeV is considered in the data reductions. Our main conclusions are: (1) all fit results present agreement with the experimental data analyzed and the goodness-of-fit is slightly better in case of the DDR approach; (2) by considering only the TOTEM data at the LHC region, the fits with L$\gamma$ indicate $\gamma \sim 2.0\pm 0.2$ (AU) and $\gamma \sim 2.3\pm 0.1$ (DDR); (3) by including the ATLAS data the fits provide $\gamma \sim 1.9\pm 0.1$ (AU) and $\gamma \sim 2.2\pm 0.2$ (DDR); (4) in the formal and practical contexts, the DDR approach is more adequate for the energy interval investigated than the AU approach. A review on the analytic results for ${\sigma }_{tot}$ and $\rho$ from the Regge-Gribov, DDR and AU approaches is presented.

    hep-phhep-exInt.J.Mod.Phys.A(2017)·24 citations
17. 17*

    The Three-Loop Splitting Functions $P_{qg}^{(2)}$ and $P_{gg}^{(2,N_F)}$

    J. Ablinger🇦🇹 · A. Behring🇩🇪 · J. Blümlein🇩🇪 · A. De Freitas🇩🇪 · A. von Manteuffel🇺🇸 · C. Schneider🇦🇹

    We calculate the unpolarized twist-2 three-loop splitting functions $P_{qg}^{(2)}(x)$ and $P_{gg}^{(2,{\mathrm{N}}_{\mathrm{F}})}(x)$ and the associated anomalous dimensions using massive three-loop operator matrix elements. While we calculate $P_{gg}^{(2,{\mathrm{N}}_{\mathrm{F}})}(x)$ directly, $P_{qg}^{(2)}(x)$ is computed from 1200 even moments, without any structural prejudice, using a hierarchy of recurrences obtained for the corresponding operator matrix element. The largest recurrence to be solved is of order 12 and degree 191. We confirm results in the foregoing literature.

    hep-phhep-exhep-thNPB(2017)·82 citations
18. 18*

    Resonance decay dynamics and their effects on $p_T$-spectra of pions in heavy-ion collisions

    Pok Man Lo🇵🇱

    We examine the influence of resonance decay dynamics on momentum spectra of pions in heavy-ion collisions. Taking the decay $\omega \to 3\pi$ as an example, we demonstrate how details of the decay matrix element can modify the physical observables. Such a dynamical effect is commonly neglected in statistical models. To remedy the situation, we formulate a theoretical framework for incorporating hadron dynamics into the analysis, which can be straightforwardly extended to describe general N-body decays.

    hep-phPRC(2018)·16 citations
19. 19*

    A natural $S_4\times SO(10)$ model of flavour

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

    We propose a natural $S_4\times SO(10)$ supersymmetric grand unified theory of flavour with an auxiliary ${\mathbb{Z}}_4^2\times {\mathbb{Z}}_4^R$ symmetry, based on small Higgs representations (nothing larger than an adjoint) and hence a type-I seesaw mechanism. The Yukawa structure of all fermions is determined by the hierarchical vacuum expectation values of three $S_4$ triplet flavons, with CSD3 vacuum alignments, where up-type quarks and neutrinos couple to one Higgs $10$, and the down-type quarks and charged leptons couple to a second Higgs $10$. The Yukawa matrices are obtained from sums of low-rank matrices, where each matrix in the sum naturally accounts for the mass of a particular family, as in sequential dominance in the neutrino sector, which predicts a normal neutrino mass hierarchy. The model accurately fits all available quark and lepton data, with predictions for the leptonic $CP$ phase in 95$\%$ credible intervals given by $281^{\circ }<{\delta }^{\ell }<308^{\circ }$ and $225^{\circ }<{\delta }^{\ell }<253^{\circ }$. The model reduces to the MSSM, with the two Higgs doublets emerging from the two Higgs $10$s without mixing, and we demonstrate how a $\mu$ term of $\mathcal{O}$(TeV) can be realised, as well as doublet-triplet splitting, with Planck scale operators controlled by symmetry, leading to acceptable proton decay.

    hep-phJHEP(2017)·32 citations
20. 20*

    Multi moment cancellation of participant fluctuations - MMCP method

    Viktor Begun🇵🇱 · Maja Mackowiak-Pawlowska🇵🇱

    We propose a new way to correct for finite centrality bin width effect i.e. participant fluctuations in fluctuation analysis in high energy nucleus-nucleus collisions. The MMCP method allows to separate participant fluctuations and obtain fluctuations from one participant - a source - from a combination of the experimentally measured first four moments. The EPOS model is used for the numerical check of the MMCP for the net electric charge fluctuations in the forward rapidity region in Ar+Sc reactions at beam momentum 150 GeV/c. We show that using the existing methods - decreasing a centrality bin width, or using the Centrality Bin Width Correction procedure, one may still leave some residual participant fluctuations in the sample. Moreover, we show that the Centrality Bin Width Correction procedure may alter the fluctuation measures. The most important advantage of the MMCP is it's precision even when the amount of measured events does not allow to decrease the centrality bin width, or the experimental determination of participants is difficult, e.g. in collider experiments. Even for the largest centrality bin in the considered case, $c=0-20\%$, the relative error of the MMCP for the scaled variance of a source is below 2\%. It is especially important in determination of the base line of the fluctuations in the search for the QCD Critical Point and the signals of the QCD phase transition.

    ↳ nucl-thhep-exhep-phnucl-ex6 citations
21. 21*

    Spatial distribution of radionuclides in 3D models of SN 1987A and Cas A

    H.-Thomas Janka (1)🇩🇪 · Michael Gabler (1) · Annop Wongwathanarat (2) ((1) MPI Astrophysics, (2) RIKEN)🇯🇵

    Fostered by the possibilities of multi-dimensional computational modeling, in particular the advent of three-dimensional (3D) simulations, our understanding of the neutrino-driven explosion mechanism of core-collapse supernovae (SNe) has experienced remarkable progress over the past decade. First self-consistent, first-principle models have shown successful explosions in 3D, and even failed cases may be cured by moderate changes of the microphysics inside the neutron star (NS), better grid resolution, or more detailed progenitor conditions at the onset of core collapse, in particular large-scale perturbations in the convective Si and O burning shells. 3D simulations have also achieved to follow neutrino-driven explosions continuously from the initiation of the blast wave, through the shock breakout from the progenitor surface, into the radioactively powered evolution of the SN, and towards the free expansion phase of the emerging remnant. Here we present results from such simulations, which form the basis for direct comparisons with observations of SNe and SN remnants in order to derive constraints on the still disputed explosion mechanism. It is shown that predictions based on hydrodynamic instabilities and mixing processes associated with neutrino-driven explosions yield good agreement with measured NS kicks, light-curve properties of SN 1987A, and asymmetries of iron and 44Ti distributions observed in SN 1987A and Cassiopeia A.

    ↳ astro-ph.HEastro-ph.SRhep-phIAU Symp.(2017)·9 citations
22. 22*

    A new bound on the low reheating temperature with dark matter

    Ki-Young Choi🇰🇷 · Tomo Takahashi🇯🇵

    We investigate a new bound on the low reheating temperature in a scenario where the Universe experiences early matter-domination before reheating after which the standard big bang cosmology begins. In many models of dark matter (DM), the small scale fluctuations of DM grow during the early matter-domination era and seed the formation of the ultracompact minihalos (UCMHs). Using the constraints on the number of UCMHs from gamma-ray observations, we find a lower bound on the reheating temperature between $\mathcal{O}(10)\mathrm{MeV}-\mathcal{O}(100)\mathrm{MeV}$ for WIMP dark matter depending on the nature of DM. A similar bound could be obtained for non-WIMP dark matter by observing UCMHs gravitationally such as pulsar timing, microlensing and so on in some future observations.

    ↳ astro-ph.COhep-phPRD(2017)·17 citations
23. 23*

    Higher moments of net-proton multiplicity distributions in a heavy-ion event pile-up scenario

    P. Garg🇺🇸 · D. K. Mishra🇮🇳

    High-luminosity modern accelerators, like the Relativistic Heavy Ion Collider (RHIC) at BNL and Large Hadron Collider (LHC) at CERN, inherently have event pile-up scenarios which significantly contribute to physics events as a background. While state-of-the-art tracking algorithms and detector concepts take care of these event pile-up scenarios, several offline analytical techniques are used to remove such events from the physics analysis. It is still difficult to identify the remaining pile-up events in an event sample for physics analysis. Since the fraction of these events is significantly small, it may not be as serious of an issue for other analysis as it would be for an event-by-event analysis. Particularly, when the characteristics of the multiplicity distribution are observable, one needs to be very careful. In the present work, we demonstrate how a small fraction of residual pile-up events can change the moments and their ratios of an event-by-event net-proton multiplicity distribution, which are sensitive to the dynamical fluctuations due to the QCD critical point. For this study we assume that the individual event-by-event proton and antiproton multiplicity distributions follow Poisson, negative binomial or binomial distributions. We observe a significant effect in cumulants and their ratios of net-proton multiplicity distributions due to pile-up events, particularly at lower energies. It might be crucial to estimate the fraction of pile-up events in the data sample while interpreting the experimental observable for the critical point.

    ↳ nucl-thhep-phnucl-exPRC(2017)·12 citations
24. 24*

    Generalized statistical mechanics of cosmic rays: Application to positron-electron spectral indices

    G. Cigdem Yalcin🇹🇷 · Christian Beck🇬🇧

    We apply generalized statistical mechanics developed for complex systems to theoretically predict energy spectra of particle and anti-particle degrees of freedom in cosmic ray fluxes, based on a $q$-generalized Hagedorn theory for transverse momentum spectra and hard QCD scattering processes. QCD at largest center of mass energies predicts the entropic index to be $q=\frac{13}{11}$, whereas the escort duality of the nonextensive thermodynamic formalism predicts an energy split of effective temperature given by $\Delta kT=\pm \frac{1}{10}k{T}_H\approx \pm 18$ MeV, where $T_H$ is the Hagedorn temperature. We carefully analyse the measured primary cosmic ray data of the AMS-02 collaboration and provide evidence that the predicted temperature split is indeed observed, leading to a different energy dependence of the $e^{+}$ and $e^{-}$ spectral indices. Moreover, we observe that at larger energies $E$ the measured $e^{+}{e}^{-}$ flux starts to deviate from our QCD-based statistical mechanics theory, with a crossover scale of $E^{\ast }=(50\pm 10)$ GeV, which could be a hint for WIMP decay or other new physics setting in at this mass scale. Fits using linear combinations of the escort and non-escort $q$-generalized canonical distributions yield excellent agreement with the measured data in the entire energy range.

    ↳ astro-ph.HEcond-mat.stat-mechhep-phSci.Rep.(2018)·17 citations
25. 25*

    Improved lattice computation of proton decay matrix elements

    Yasumichi Aoki🇯🇵 · Taku Izubuchi🇺🇸 · Eigo Shintani🇯🇵 · Amarjit Soni🇺🇸

    We present an improved result of lattice computation of the proton decay matrix elements in $N_f=2+1$ QCD. In this study, the significant improvement of statistical accuracy by adopting the error reduction technique of All-mode-averaging, is achieved for relevant form factor to proton (and also neutron) decay on the gauge ensemble of $N_f=2+1$ domain-wall fermions in $m_{\pi }=0.34$--0.69 GeV on 2.7~fm${}^3$ lattice as used in our previous work \cite{Aoki:2013yxa}. We improve total accuracy of matrix elements to 10--15\% from 30--40\% for $p\to \pi e^{+}$ or from 20--40\% for $p\to K\bar{\nu }$. The accuracy of the low energy constants $\alpha$ and $\beta$ in the leading-order baryon chiral perturbation theory (BChPT) of proton decay are also improved. The relevant form factors of $p\to \pi$ estimated through the "direct" lattice calculation from three-point function appear to be 1.4 times smaller than those from the "indirect" method using BChPT with $\alpha$ and $\beta$. It turns out that the utilization of our result will provide a factor 2--3 larger proton partial lifetime than that obtained using BChPT. We also discuss the use of these parameters in a dark matter model.

    ↳ hep-lathep-phPRD(2017)·186 citations
26. 26*

    Extracting $\hat{q}$ in event-by-event hydrodynamics and the centrality/energy puzzle

    Carlota Andres🇪🇸 · Nestor Armesto🇪🇸 · Harri Niemi🇩🇪 · Risto Paatelainen🇫🇮 · Carlos A. Salgado🇪🇸 · Pia Zurita🇺🇸

    In our analysis, we combine event-by-event hydrodynamics, within the EKRT formulation, with jet quenching -ASW Quenching Weights- to obtain high-$p_T$ $R_{\mathrm{AA}}$ for charged particles at RHIC and LHC energies for different centralities. By defining a $K$-factor that quantifies the departure of $\hat{q}$ from an ideal estimate, $K=\hat{q}/(2{ϵ}^{3/4})$, we fit the single-inclusive experimental data for charged particles. This $K$-factor is larger at RHIC than at the LHC but, surprisingly, it is almost independent of the centrality of the collision.

    ↳ nucl-thhep-phnucl-exNPA(2017)·8 citations
27. 27*

    Does the detection of primordial gravitational waves exclude low energy inflation?

    Tomohiro Fujita🇯🇵 · Ryo Namba🇨🇦 · Yuichiro Tada🇯🇵

    We show that a detectable tensor-to-scalar ratio $(r\ge 10^{-3})$ on the CMB scale can be generated even during extremely low energy inflation which saturates the BBN bound ${\rho }_{\inf }\approx (30\mathrm{MeV}{)}^4$. The source of the gravitational waves is not quantum fluctuations of graviton but those of $SU(2)$ gauge fields, energetically supported by coupled axion fields. The curvature perturbation, the backreaction effect and the validity of perturbative treatment are carefully checked. Our result indicates that measuring $r$ alone does not immediately fix the inflationary energy scale.

    ↳ astro-ph.COgr-qchep-phhep-thPLB(2018)·59 citations
28. 28*

    A note on polarized light from Magnetars

    L.M. Capparelli🇮🇹 · A. Damiano🇮🇹 · L. Maiani🇨🇭 · A.D. Polosa🇮🇹

    In a recent paper it is claimed that vacuum birefringence has been experimentally observed for the first time by measuring the degree of polarization of visible light from a Magnetar candidate, a neutron star with a magnetic field presumably as large as $B\sim 10^{13}$~G. The role of such a strong magnetic field is twofold. First, the surface of the star emits, at each point, polarized light with linear polarization correlated with the orientation of the magnetic field. Depending on the relative orientation of the magnetic axis of the star with the direction to the distant observer, a certain degree of polarization should be visible. Second, the strong magnetic field in the vacuum surrounding the star could enhance the effective degree of polarization observed: vacuum birefringence. We compare experimental data and theoretical expectations concluding that the conditions to support a claim of strong evidence of vacuum birefringence effects are not met.

    ↳ astro-ph.HEhep-phEPJC(2017)·34 citations
29. 29*

    Superradiant instability of massive vector fields around spinning black holes in the relativistic regime

    William E. East🇨🇦

    We study the superradiant instability of massive vector fields, i.e. Proca fields, around spinning black holes in the test field limit. This is motivated by the possibility that observations of astrophysical black holes can probe the existence of ultralight bosons subject to this mechanism. By making use of time-domain simulations, we characterize the growth rate, frequency, spatial distribution, and other properties of the unstable modes, including in the regime where the black hole is rapidly spinning and the Compton wavelength of the Proca field is comparable to the black hole radius. We find that relativistic effects in this regime increase the range of Proca masses that are unstable, as well as the maximum instability rate. We also study the gravitational waves that can be sourced by such an instability, finding that they can be significantly stronger than in the massive scalar field case.

    ↳ gr-qcastro-ph.HEhep-phPRD(2017)·165 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.