Thu·Jul 28, 2016Thursday·July 28, 2016

1. 01*

   Challenges for models with composite states

   James M. Cline🇨🇦 · Weicong Huang🇨🇳 · Guy D. Moore🇩🇪

   Composite states of electrically charged and QCD-colored hyperquarks (HQs) in a confining SU(N_HC) hypercolor gauge sector are a plausible extension of the standard model at the TeV scale, and have been widely considered as an explanation for the tentative LHC diphoton excess. Additional new physics is required to avoid a stable charged hyperbaryon in such theories. We classify renormalizable models allowing the decay of this unwanted relic directly into standard model states, showing that they are significantly restricted if the new scalar states needed for UV completion are at the TeV scale. Alternatively, if hyperbaryon number is conserved, the charged relic can decay into a neutral hyperbaryon. Such theories are strongly constrained by direct detection, if the neutral constituent hyperquark carries color or weak isospin, and by LHC searches for leptoquarks if it is a color singlet. We show that the neutral hyperbaryon can have the observed relic abundance if the confinement scale and the hyperquark mass are above TeV scale, even in the absence of any hyperbaryon asymmetry.

   hep-phPRD(2016)·38 citations
2. 02*

   Constraining wrong-sign $hbb$ couplings with $h\to {\rm Y}\gamma$

   Tanmoy Modak🇮🇳 · Jorge C. Romão🇵🇹 · Soumya Sadhukhan🇮🇳 · João P. Silva🇵🇹 · Rahul Srivastava🇮🇳

   The rare decay $h\to {\rm Y}\gamma$ has a very small rate in the Standard Model, due to a strong cancellation between the direct and indirect diagrams. Models with a changed $hbb$ coupling can thus lead to a great increase in this decay. Current limits on two Higgs doublet models still allow for the possibility that the $hbb$ coupling might have a sign opposite to the Standard Model; the so-called "wrong-sign". We show how $h\to {\rm Y}\gamma$ can be used to put limits on the wrong-sign solutions.

   hep-phhep-exPRD(2016)·32 citations
3. 03*

   Perspectives for tests of neutrino mass generation at the GeV scale: Experimental reach versus theoretical predictions

   Rasmus W. Rasmussen🇩🇪 · Walter Winter🇩🇪

   We discuss the parameter space reach of future experiments searching for heavy neutral leptons (HNLs) at the GeV scale in terms of neutrino mass models with three HNL generations. We focus on two classes of models: Generic assumptions (such as random mass matrices or the Casas-Ibarra parameterization) and flavor symmetry-generated models. We demonstrate that the generic approaches lead to comparable parameter space predictions, which tend to be at least partially within the reach of future experiments. On the other hand, specific flavor symmetry models yield more refined predictions, some of these can be more clearly excluded. We also highlight the importance to measure the flavor-dependent couplings of the HNLs as a model discriminator, and we clarify the impact of assumptions frequently used in the literature to show the parameter space reach for the active-sterile mixings.

   hep-phhep-exPRD(2016)·19 citations
4. 04*

   A principle for the Yukawa couplings

   U. J. Saldana-Salazar🇲🇽

   Yukawa couplings in the Standard Model are introduced in its most general form, that is, completely arbitrary complex numbers. Here we show that their origin could not be general but dictated by a principle.

   hep-phJ.Phys.Conf.Ser.(2016)·5 citations
5. 05*

   Simple Mass Estimate for Resonance(s) being 6 Top plus 6 Anti top Bound states and Combinations thereof

   Holger Bech Nielsen🇩🇰

   We have long speculated \cite{1nbs,2nbs,3nbs,4nbs,5nbs, 6nbs,7nbs,8nbs,9nbs,10nbs,11nbs,12nbs, 13nbs,14nbs,LNvacuumstability} , that 6 top + 6 anti-top quarks due to the realtively large size of the top-yukawa coupling would bind exceptionaly strongly by mainly Higgs exchange. Here we present a surprisingly simple "calculation" of the mass of this speculated bound state. Even a possible resonance in scattering of two such bound states is speculated. For the "calculation" of the masses it is crucial to assume, that our since long speculated principle "Multiple Point Principle"\cite{5mp,6mp,7mp,8mp,9mp,10mp, 11mp,12mp,13mp,14mp,15mp,16mp,17mp, deriving}, is true. This principle says: {\em there are several vacua all having almost zero energy density}. Further we make an approximation of the Higgs Yukawa potential essentially replacing the exponential in it by a step-function. The new result means that there are now two independent calls for our bound state having the mass around 750 GeV required by our "new law of nature" the Multiple Point Principle. It should be remarked that in our picture there is {\em no new physics} in the sense of new fundamental particles, but the "Multiple Point Principle" is new in the sense of being not yet accepted. Further we get the {\em same} mass within uncertainties as earlier\cite{LNvacuumstability} but now from a completly different assumption, except for being from our "multiple point principle". But the two masses are gotten from using {\em different} (speculative) vacua occuring in the pure Standard Model.

   hep-phInt.J.Mod.Phys.A(2016)·3 citations
6. 06*

   Strongly Enhanced Effects of Lorentz-Symmetry Violation in Yb${}^{+}$ and Highly Charged Ions

   M.S. Safronova🇺🇸

   A Lorentz-symmetry test with Ca${}^{+}$ ions demonstrated the potential of using quantum information inspired technology for tests of fundamental physics. A systematic study of atomic-system sensitivities to Lorentz violation identified the ytterbium ion as an ideal system with high sensitivity as well as excellent experimental controllability. A test of Lorentz-violating physics in the electron-photon sector with Yb${}^{+}$ ions has the potential to reach levels of 10${}^{-23}$, five orders of magnitude more sensitive than the current best bounds. Similar sensitivities may be also reached with highly charged ions.

   hep-phphysics.atom-phquant-ph0 citations
7. 07*

   Kondo effect of ${\bar{D}}_s$ and ${\bar{D}}_s^{\ast }$ mesons in nuclear matter

   Shigehiro Yasui🇯🇵 · Kazutaka Sudoh🇯🇵

   We study the Kondo effect for ${\bar{D}}_s$ and ${\bar{D}}_s^{\ast }$ mesons as impurity particles in nuclear matter. The spin-exchange interaction between the ${\bar{D}}_s$ or ${\bar{D}}_s^{\ast }$ meson and the nucleon induces the enhancement of the effective coupling in the low-energy scattering in the infrared region, whose scale of singularity is given by the Kondo scale. We investigate the Kondo scale in the renormalization group equation at nucleon one-loop level. We furthermore study the ground state with the Kondo effect in the mean-field approach, and present that the Kondo scale is related to the mixing strength between the ${\bar{D}}_s$ or ${\bar{D}}_s^{\ast }$ meson and the nucleon in nuclear matter. We show the spectral function of the impurity when the Kondo effect occurs.

   hep-phcond-mat.str-elPRC(2017)·22 citations
8. 08*

   Phenomenological aspects from vacuum stability and metastability in models with soft breaking of a $U\left(1\right)$ global symmetry

   Andrés Castillo🇨🇴 · Rodolfo A. Diaz🇨🇴 · John Morales🇨🇴 · Carlos G. Tarazona🇨🇴

   We study the vacuum behavior of an extended Higgs sector with two doublets in a scenario with a softly broken $U(1)$ global symmetry. The soft-violation term is introduced to avoid massless-axion particles arising when the global symmetry becomes spontaneously broken. This model has metastable states through the possible presence of multiple non-degenerate minima, which is unwanted from the phenomenological point of view if the metastable state is not long-lived enough. The analysis of this fact leads to find possible exclusion limits over parameter space of quartic couplings. Results improve the individual behavior of initial conditions for renormalization group equations; also determining unstable zones for the effective Higgs potential at one loop level. Besides vacuum stability analyses, the influence of absence of charge violation minima is considered as a limiting case excluding zones in the parameter space. Extremal cases for the model as well as criticality phenomena are discussed with the aid of relation among Higgs masses or splittings among them. From vacuum behavior and LHC results, phenomenological aspects in the searching of charged and heavier Higgs bosons are considered to evaluate the scalar alignment regimen of the two Higgs doublet model.

   hep-ph2 citations
9. 09*

   Factorization of the dijet cross section in hadron-hadron collisions

   Junegone Chay🇰🇷 · Taewook Ha🇰🇷 · Taehyun Kwon🇰🇷

   The factorization theorem for the dijet cross section is presented in hadron-hadron collisions with a cone-type jet algorithm. We also apply the beam veto to the beam jets consisting of the initial radiation. The soft-collinear effective theory is employed to see the factorization structure transparently when there are four distinct lightcone directions involved. There are various types of divergences such as the ultraviolet and infrared divergences. And when the phase space is divided to probe the collinear and the soft parts, there appears an additional divergence called rapidity divergence. These divergences are sorted out and we will show that all the infrared and rapidity divergences cancel, and only the ultraviolet divergence remains. It is a vital step to justify the factorization. Among many partonic processes, we take $q\overline{q}\to gg$ as a specific example to consider the dijet cross section. The hard and the soft functions have nontrivial color structure, while the jet and the beam functions are diagonal in operator basis. The dependence of the soft anomalous dimension on the jet algorithm and the beam veto is diagonal in operator space, and is cancelled by that of the jet and beam functions. We also compute the anomalous dimensions of the factorized components, and resum the large logarithms to next-to-leading logarithmic accuracy by solving the renormalization group equation.

   hep-phJ.Korean Phys.Soc.(2021)·0 citations
10. 10*

    Light speed variation from gamma ray burst GRB 160509A

    Haowei Xu🇨🇳 · Bo-Qiang Ma🇨🇳

    It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed. Even a tiny speed variation, when amplified by the cosmological distance, may be revealed by the observed time lags between photons with different energies from astrophysical sources. From the newly detected long gamma ray burst GRB~160509A, we find evidence to support the prediction for a linear form modification of light speed in cosmological space.

    hep-phastro-ph.HEgr-qcPLB(2016)·98 citations
11. 11*

    Deviations in Tribimaximal Mixing From Sterile Neutrino Sector

    S. Dev🇮🇳 · Desh Raj🇮🇳 · Radha Raman Gautam🇮🇳

    We explore the possibility of generating a non-zero $U_{e3}$ element of the neutrino mixing matrix from tribimaximal neutrino mixing by adding a light sterile neutrino to the active neutrinos. Small active-sterile mixing can provide the necessary deviation from tribimaximal mixing to generate a non-zero ${\theta }_{13}$ and atmospheric mixing ${\theta }_{23}$ different from maximal. Assuming no CP-violation, we study the phenomenological impact of sterile neutrinos in the context of current neutrino oscillation data. The tribimaximal pattern is broken in such a manner that the second column of tribimaximal mixing remains intact in the neutrino mixing matrix.

    hep-phNPB(2016)·11 citations
12. 12*

    Limiting First Order Phase Transitions in Dark Gauge Sectors from Gravitational Waves experiments

    Andrea Addazi🇮🇹

    We discuss the possibility to indirectly test First Order Phase Transitions of hidden sectors. We study the interesting example of a {\it dark standard model} with a deformed parameter space in the Higgs potential. A dark electroweak phase transition can be limited from next future experiments like eLISA and DECIGO.

    hep-phgr-qcMod.Phys.Lett.A(2017)·45 citations
13. 13*

    Correspondence of Many-flavor Limit and Kaluza-Klein Degrees of Freedom in the Description of Compact Stars

    Szilvia Karsai🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Emese Forgács-Dajka🇭🇺 · Péter Pósfay🇭🇺

    We present the correspondence between non-interacting multi-hadron fermion star equation of state in the many-flavor limit and the degrees of freedom of a Kaluza\,--\,Klein compact star. Many flavors can be interpreted in this framework as one extra compacti\-fied spatial dimension with various, more-and-more massive hadron state excitations. The effect of increasing the degrees of freedom was investigated on the equation of state and in connection with the mass-radius relation, $M(R)$. The maximum mass of the star, $M_{\max }$ were also calculated as a function of the maximum number of excited states, $n$ and the size of the compactified extra dimension, $R_{\mathrm{c}}$.

    hep-phastro-ph.HEgr-qcActa Phys.Polon.Supp.(2017)·3 citations
14. 14*

    Electroweak Vacuum Instability and Renormalized Higgs Field Vacuum Fluctuations in the Inflationary Universe

    Kazunori Kohri🇯🇵 · Hiroki Matsui🇯🇵

    In this work, we investigated the electroweak vacuum instability during or after inflation. In the inflationary Universe, i.e., de Sitter space, the vacuum field fluctuations $⟨{\delta \varphi }^2⟩$ enlarge in proportion to the Hubble scale $H^2$. Therefore, the large inflationary vacuum fluctuations of the Higgs field $⟨{\delta \varphi }^2⟩$ are potentially catastrophic to trigger the vacuum transition to the negative-energy Planck-scale vacuum state and cause an immediate collapse of the Universe. However, the vacuum field fluctuations $⟨{\delta \varphi }^2⟩$, i.e., the vacuum expectation values have an ultraviolet divergence, and therefore a renormalization is necessary to estimate the physical effects of the vacuum transition. Thus, in this paper, we revisit the electroweak vacuum instability from the perspective of quantum field theory (QFT) in curved space-time, and discuss the dynamical behavior of the homogeneous Higgs field $\varphi$ determined by the effective potential $V_{\mathrm{eff}}\left(\varphi \right)$ in curved space-time and the renormalized vacuum fluctuations ${⟨{\delta \varphi }^2⟩}_{\mathrm{ren}}$ via adiabatic regularization and point-splitting regularization. We simply suppose that the Higgs field only couples the gravity via the non-minimal Higgs-gravity coupling $\xi (\mu )$. In this scenario, the electroweak vacuum stability is inevitably threatened by the dynamical behavior of the homogeneous Higgs field $\varphi$, or the formations of AdS domains or bubbles unless the Hubble scale is small enough $H<{\Lambda }_I$.

    hep-phastro-ph.COgr-qchep-thJCAP(2017)·29 citations
15. 15*

    Finite-size corrections to Fermi's Golden rule II: Quasi-stationary composite states

    Kenzo Ishikawa🇯🇵 · Yutaka Tobita🇯🇵

    Many-body states described by a Schrödinger equation include states of overlapping waves of non-vanishing interaction energies. These peculiar states formed in many-body transitions remain in asymptotic regions, and lead a new component to the transition probability. The probability is computed rigorously following the von Neumann's fundamental principle of quantum mechanics with an S-matrix that is defined with normalized functions, instead of plane waves. That includes the intriguing correction term to the Fermi's golden rule, in which a visible energy is smaller than the initial energy, and reveals macroscopic quantum phenomena for light particles. Processes in Quantum Electrodynamics are analyzed and the sizable corrections are found in the dilute systems. The results suggest that these states play important roles in natural phenomena, and the verification in laboratory would be possible with recent advanced technology.

    hep-phquant-ph6 citations
16. 16*

    Features from the non-attractor beginning of inflation

    Yi-Fu Cai🇨🇳 · Jinn-Ouk Gong🇰🇷 · Dong-Gang Wang🇨🇳 · Ziwei Wang🇨🇳

    We study the effects of the non-attractor initial conditions for the canonical single-field inflation. The non-attractor stage can last only several $e$-folding numbers, and should be followed by hilltop inflation. This two-stage evolution leads to large scale suppression in the primordial power spectrum, which is favored by recent observations. Moreover we give a detailed calculation of primordial non-Guassianity due to the "from non-attractor to slow-roll" transition, and find step features in the local and equilateral shapes. We conclude that a plateau-like inflaton potential with an initial non-attractor phase yields interesting features in both power spectrum and bispectrum.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2016)·54 citations
17. 17*

    Nuclear Physics Meets the Sources of the Ultra-High Energy Cosmic Rays

    Denise Boncioli🇩🇪 · Anatoli Fedynitch🇩🇪 · Walter Winter🇩🇪

    The determination of the injection composition of cosmic ray nuclei within astrophysical sources requires sufficiently accurate descriptions of the source physics and the propagation - apart from controlling astrophysical uncertainties. We therefore study the implications of nuclear data and models for cosmic ray astrophysics, which involves the photo-disintegration of nuclei up to iron in astrophysical environments. We demonstrate that the impact of nuclear model uncertainties is potentially larger in environments with non-thermal radiation fields than in the cosmic microwave background. We also study the impact of nuclear models on the nuclear cascade in a gamma-ray burst radiation field, simulated at a level of complexity comparable to the most precise cosmic ray propagation code. We conclude with an isotope chart describing which information is in principle necessary to describe nuclear interactions in cosmic ray sources and propagation.

    ↳ astro-ph.HEhep-phnucl-exnucl-thSci.Rep.(2017)·55 citations
18. 18*

    Lindblad Equation for the Inelastic Loss of Ultracold Atoms

    Eric Braaten🇺🇸 · H.-W. Hammer🇩🇪 · G. Peter Lepage🇺🇸

    The loss of ultracold trapped atoms due to deeply inelastic reactions has previously been taken into account in effective field theories for low-energy atoms by adding local anti-Hermitian terms to the effective Hamiltonian. Here we show that when multi-atom systems are considered, an additional modification is required in the equation governing the density matrix. We define an effective density matrix by tracing over the states containing high-momentum atoms produced by deeply inelastic reactions. We show that it satisfies a Lindblad equation, with local Lindblad operators determined by the local anti-Hermitian terms in the effective Hamiltonian. We use the Lindblad equation to derive the universal relation for the two-atom inelastic loss rate for fermions with two spin states and the universal relation for the three-atom inelastic loss rate for identical bosons.

    ↳ cond-mat.quant-gashep-phPRA(2017)·31 citations
19. 19*

    Magnetic field effects on the static quark potential at zero and finite temperature

    Claudio Bonati🇮🇹 · Massimo D'Elia🇮🇹 · Marco Mariti🇮🇹 · Michele Mesiti🇮🇹 · Francesco Negro🇮🇹 · Andrea Rucci🇮🇹 · Francesco Sanfilippo🇬🇧

    We investigate the static $Q\bar{Q}$ potential at zero and finite temperature in the presence of a constant and uniform external magnetic field $\vec{B}$, for several values of the lattice spacing and for different orientations with respect to $\vec{B}$. As a byproduct, we provide continuum limit extrapolated results for the string tension, the Coulomb coupling and the Sommer parameter at $T=0$ and $B=0$. We confirm the presence in the continuum of a $B$-induced anisotropy, regarding essentially the string tension, for which it is of the order of 15\% at $|e|B\sim 1{\mathrm{GeV}}^2$ and would suggest, if extrapolated to larger fields, a vanishing string tension along the magnetic field for $|e|B\gtrsim 4$ GeV${}^2$. The angular dependence for $|e|B\lesssim 1$ GeV${}^2$ can be nicely parametrized by the first allowed term in an angular Fourier expansion, corresponding to a quadrupole deformation. Finally, for $T\ne 0$, the main effect of the magnetic field is a general suppression of the string tension, leading to a precocious loss of the confining properties: this happens even before the appearance of inverse magnetic catalysis in the chiral condensate, supporting the idea that the influence of the magnetic field on the confining properties is the leading effect originating the decrease of $T_c$ as a function of $B$.

    ↳ hep-lathep-phPRD(2016)·104 citations
20. 20*

    Lattice calculation of the pion transition form factor ${\pi }^0\to {\gamma }^{\ast }{\gamma }^{\ast }$

    Antoine Gérardin🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪

    We calculate the ${\pi }^0\to {\gamma }^{\ast }{\gamma }^{\ast }$ transition form factor ${\mathcal{F}}_{{\pi }^0{\gamma }^{\ast }{\gamma }^{\ast }}(q_1^2,q_2^2)$ in lattice QCD with two flavors of quarks. Our main motivation is to provide the input to calculate the ${\pi }^0$-pole contribution to hadronic light-by-light scattering in the muon $(g-2)$, $a_{\mu }^{\mathrm{HLbL};{\pi }^0}$. We therefore focus on the region where both photons are spacelike up to virtualities of about $1.5$GeV${}^2$, which has so far not been experimentally accessible. Results are obtained in the continuum at the physical pion mass by a combined extrapolation. We reproduce the prediction of the chiral anomaly for real photons with an accuracy of about $8-9\%$. We also compare to various recently proposed models and find reasonable agreement for the parameters of some of these models with their phenomenological values. Finally, we use the parametrization of our lattice data by these models to calculate $a_{\mu }^{\mathrm{HLbL};{\pi }^0}$.

    ↳ hep-lathep-phPRD(2016)·100 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.