Mon·Nov 20, 2017Monday·November 20, 2017

1. 01*

   Loopholes in $Z^{\prime }$ searches at the LHC: exploring supersymmetric and leptophobic scenarios

   Jack Y. Araz🇨🇦 · Gennaro Corcella🇮🇹 · Mariana Frank🇨🇦 · Benjamin Fuks🇫🇷

   Searching for heavy vector bosons $Z^{\prime }$, predicted in models inspired by Grand Unification Theories, is among the challenging objectives of the LHC. The ATLAS and CMS collaborations have looked for $Z^{\prime }$ bosons assuming that they can decay only into Standard Model channels, and have set exclusion limits by investigating dilepton, dijet and to a smaller extent top-antitop final states. In this work we explore possible loopholes in these $Z^{\prime }$ searches by studying supersymmetric as well as leptophobic scenarios. We demonstrate the existence of realizations in which the $Z^{\prime }$ boson automatically evades the typical bounds derived from the analyses of the Drell-Yan invariant-mass spectrum. Dileptonic final states can in contrast only originate from supersymmetric $Z^{\prime }$ decays and are thus accompanied by additional effects. This feature is analyzed in the context of judiciously chosen benchmark configurations, for which visible signals could be expected in future LHC data with a $4\sigma -7\sigma$ significance. Our results should hence motivate an extension of the current $Z^{\prime }$ search program to account for supersymmetric and leptophobic models.

   hep-phJHEP(2018)·32 citations
2. 02*

   Approaching the asymptotics at the LHC

   Norbert Bence🇺🇦 · László Jenkovszky🇺🇦 · István Szanyi🇺🇦

   Recent results on the slope of the $pp$ diffraction cone measured by TOTEM at $7$ and $8$ GeV show an unexpected rapid rise in $s$, close to $B(s)\sim {\ln }^2$, rather than $\ln s$, typical of the Regge-pole predictions. We show that the new phenomenon can be accommodated by the inclusion of unitarity corrections to a simple Regge (pomeron) pole exchange. Interestingly, the odderon may also promote the acceleration of $B(s)$. The onset of the new regime may be indicative of the approach to the asymptotic dynamics of strong interactions. We analyse the new data together with other available forward measurable in a unitarized Regge dipole. Unitarization proves crucial in fitting the data, especially those on the slope $B(s)$ showing a change from the $\ln (s)$ to ${\ln }^2(s)$ behavior. Having fitted the free parameters of the unitarized model to the data, we predict the behavior of the cross sections and the slope at still higher energies, including those asymptotic.

   hep-phhep-ex2 citations
3. 03*

   Positivity bound on the imaginary part of the right-chiral tensor coupling $g_R$ in polarized top quark decay

   S. Groote🇪🇪 · J.G. Körner🇩🇪

   We derive a positivity bound on the right-chiral tensor coupling Im $g_R$ in polarized top quark decay by analyzing the angular decay distribution of the three-body polarized top quark decay $t(\uparrow )\to b+{\ell }^{+}+{\nu }_{\ell }$ in NLO QCD. We obtain the bound $-0.0420\le$ Im $g_R\le 0.0420$.

   hep-phhep-exPRD(2017)·3 citations
4. 04*

   The Higgs properties in the MSSM after the LHC Run-2

   Jun Zhao🇨🇳

   We scrutinize the parameter space of the SM-like Higgs boson in the minimal supersymmetric standard model (MSSM) under current experimental constraints. The constraints are from (i) the precison electroweak data and various flavor observables; (ii) the direct 22 separate ATLAS searches in Run-1; (iii) the latest LHC Run-2 Higgs data and tri-lepton search of electroweakinos. We perform a scan over the parameter space and find that the Run-2 data can further exclude a part of parameter space. For the property of the SM-like Higgs boson, its gauge couplings further approach to the SM values with a deviation below 0.1\%, while its Yukawa couplings $hb\bar{b}$ and $h\tau \bar{\tau }$ can still sizably differ from the SM predictions by several tens percent.

   hep-phastro-ph.HEhep-exInt.J.Mod.Phys.A(2018)·2 citations
5. 05*

   Scattering of charmed baryons on nucleons

   J. Haidenbauer🇩🇪 · G. Krein🇧🇷

   Chiral effective field theory is utilized for extrapolating results on the ${\Lambda }_{c}N$ interaction, obtained in lattice QCD at unphysical (large) quark masses, to the physical point. The pion-mass dependence of the components that constitute the ${\Lambda }_{c}N$ potential up to next-to-leading order (pion-exchange diagrams and four-baryon contact terms) is fixed by information from lattice QCD simulations. No recourse to SU(3) or SU(4) flavor symmetry is made. It is found that the results of the HAL QCD Collaboration for quark masses corresponding to $m_{\pi }=410$--$570$ MeV imply a moderately attractive ${\Lambda }_{c}N$ interaction at $m_{\pi }=138$ MeV with scattering lengths of $a\approx -1$ fm for the ${}^1{S}_0$ as well as the ${}^3{S}_1$ partial waves. For such an interaction the existence of a charmed counterpart of the hypertriton is unlikely but four- and/or five-baryons systems with a ${\Lambda }_c$ baryon could be indeed bound.

   hep-phnucl-thEPJA(2018)·34 citations
6. 06*

   Semi-aligned two Higgs doublet model

   Naoyuki Haba🇯🇵 · Hiroyuki Umeeda🇯🇵 · Toshifumi Yamada🇯🇵

   In the left-right symmetric model based on $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ gauge symmetry, there appear heavy neutral scalar particles mediating quark flavor changing neutral currents (FCNCs) at tree level. We consider a situation where such FCNCs give the only sign of the left-right model while $W_R$ gauge boson is decoupled, and name it "semi-aligned two Higgs doublet model" because the model resembles a two Higgs doublet model with mildly-aligned Yukawa couplings to quarks. We predict a correlation among processes induced by quark FCNCs in the model, and argue that future precise calculation of meson-antimeson mixings and CP violation therein may hint at the semi-aligned two Higgs doublet model and the left-right model behind it.

   hep-phPRD(2018)·5 citations
7. 07*

   Cosmological abundance of the QCD axion coupled to hidden photons

   Naoya Kitajima🇯🇵 · Toyokazu Sekiguchi🇰🇷 · Fuminobu Takahashi🇯🇵

   We study the cosmological evolution of the QCD axion coupled to hidden photons. For a moderately strong coupling, the motion of the axion field leads to an explosive production of hidden photons by tachyonic instability. We use lattice simulations to evaluate the cosmological abundance of the QCD axion. In doing so, we incorporate the backreaction of the produced hidden photons on the axion dynamics, which becomes significant in the non-linear regime. We find that the axion abundance is suppressed by at most $\mathcal{O}(10^2)$ for the decay constant $f_a=10^{16}$ GeV, compared to the case without the coupling. For a sufficiently large coupling, the motion of the QCD axion becomes strongly damped, and as a result, the axion abundance is enhanced. Our results show that the cosmological upper bound on the axion decay constant can be relaxed by a few hundred for a certain range of the coupling to hidden photons.

   hep-phastro-ph.COhep-thPLB(2018)·77 citations
8. 08*

   The Electroweak Vacuum Decay and the Gravitational Contribution

   Alberto Salvio🇨🇭

   Whether the Standard Model electroweak vacuum is stable, metastable or unstable depends crucially on the top mass (and, to a lesser extent, on other measurable quantities). These topics are reviewed and updated by taking into account the most recent determination of the top and Higgs masses. Moreover, the correction to the vacuum decay due to Einstein gravity is described. This process is also discussed in a scenario, called softened gravity, which has been proposed as a solution of the Higgs mass hierarchy problem.

   hep-ph3 citations
9. 09*

   Fully differential NNLO computations with MATRIX

   Massimiliano Grazzini🇨🇭 · Stefan Kallweit🇨🇭 · Marius Wiesemann🇨🇭

   We present the computational framework MATRIX which allows us to evaluate fully differential cross sections for a wide class of processes at hadron colliders in next-to-next-to-leading order (NNLO) QCD. The processes we consider are $2\to 1$ and $2\to 2$ hadronic reactions involving Higgs and vector bosons in the final state. All possible leptonic decay channels of the vector bosons are included for the first time in the calculations, by consistently accounting for all resonant and non-resonant diagrams, off-shell effects and spin correlations. We briefly introduce the theoretical framework MATRIX is based on, discuss its relevant features and provide a detailed description of how to use MATRIX to obtain NNLO accurate results for the various processes. We report reference predictions for inclusive and fiducial cross sections of all the physics processes considered here and discuss their corresponding uncertainties. MATRIX features an automatic extrapolation procedure that allows us, for the first time, to control the systematic uncertainties inherent to the applied NNLO subtraction procedure down to the few permille level (or better).

   hep-phhep-exEPJC(2018)·471 citations
10. 10*

    Enhanced di-Higgs Production in the Complex Higgs Singlet Model

    S. Dawson🇺🇸 · M. Sullivan🇺🇸

    We consider the Standard Model extended by the addition of a complex scalar singlet, with no assumptions about additional symmetries of the potential. This model provides for resonant di-Higgs production of Higgs particles with different masses. We demonstrate that regions of parameter space allowed by precision electroweak measurements, experimental limits on single Higgs production, and perturbative unitarity allow for large di-Higgs production rates relative to the SM rates. In this scenario, the dominant production mechanism of the new scalar states is di-Higgs production. Results are presented for $\sqrt{S}=13$, $27$ and $100TeV$.

    hep-phPRD(2018)·40 citations
11. 11*

    Global $SU(2{)}_L\otimes$BRST symmetry and its LSS theorem: Ward-Takahashi identities governing Green's functions, on-shell T-Matrix elements, and $V_{eff}$, in the scalar-sector of certain spontaneously broken non-Abelian gauge theories

    Özenç Güngör · Bryan W. Lynn · Glenn D. Starkman

    This work is dedicated to the memory of Raymond Stora (1930-2015). $SU(2{)}_L$ is the simplest spontaneous symmetry breaking (SSB) non-Abelian gauge theory: a complex scalar doublet $\varphi =\frac{1}{\sqrt{2}}\left[\begin{array}{c}H+i{\pi }_3-{\pi }_2+i{\pi }_1\end{array}\right]\equiv \frac{1}{\sqrt{2}}\tilde{H}{e}^{2i\tilde{t}\cdot \widetilde{\stackrel{⃗}{\pi }}/<H>}\left[\begin{array}{c}10\end{array}\right]$ and a vector ${\vec{W}}^{\mu }$. In Landau gauge, ${\vec{W}}^{\mu }$ is transverse, $\overrightarrow{\stackrel{~}{\pi }}$ are massless derivatively coupled Nambu-Goldstone bosons (NGB). A global shift symmetry enforces $m_{\tilde{\pi }}^2=0$. We observe that on-shell T-matrix elements of physical states ${\vec{W}}^{\mu }$,$\varphi$ are independent of global $SU(2{)}_L$ transformations, and the associated global current is exactly conserved for amplitudes of physical states. We identify two towers of "1-soft-pion" global Ward-Takahashi Identities (WTI), which govern the $\varphi$-sector, and represent a new global symmetry, $SU(2{)}_L\otimes$BRST, a symmetry not of the Lagrangian but of the physical states. The first gives relations among 1-$\varphi$-I (but one $W^{\mu },B^{\mu }$ reducible) off-shell Green's functions, the second governs on-shell T-matrix elements, replacing the Adler self-consistency conditions. These WTI constrain the all-loop-orders scalar-sector effective Lagrangian and guarantee IR finiteness of the theory. These on-shell WTI include a Lee-Stora-Symanzik (LSS) theorem, which enforces the condition $m_{\pi }^2=0$ (far stronger than $m_{\tilde{\pi }}^2=0$) and causes all relevant-operator contributions to the effective Lagrangian to vanish exactly. The global $SU(2{)}_L$ and the BRST transformations commute in $R_{\xi }$ gauges. With the on-shell T-matrix constraints, the physics therefore has more symmetry than does its BRST invariant Lagrangian. We also show that the statements made above hold for the electroweak sector of the Standard Model bosons.

    hep-phhep-th0 citations
12. 12*

    $N\pi$ scattering in the Roper channel

    M. Padmanath🇩🇪 · C. B. Lang🇦🇹 · Luka Leskovec🇺🇸 · Sasa Prelovsek🇸🇮

    We present results from our recent lattice QCD study of $N\pi$ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance $N^{\ast }(1440)$ resides in experiment. Using a variety of hadron operators, that include $qqq$-like, $N\pi$ in $p$-wave and $N\sigma$ in $s$-wave, we systematically extract the excited lattice spectrum in the nucleon channel up to 1.65 GeV. Our lattice results indicate that N$\pi$ scattering in the elastic approximation alone does not describe a low-lying Roper. Coupled channel effects between $N\pi$ and $N\pi \pi$ seem to be crucial to render a low-lying Roper in experiment, reinforcing the notion that this state could be a dynamically generated resonance. After giving a brief motivation for studying the Roper channel and the relevant technical details to this study, we will discuss the results and the conclusions based on our lattice investigation and in comparison with other lattice calculations.

    ↳ hep-lathep-phEPJ Web Conf.(2018)·4 citations
13. 13*

    Stationary black holes with stringy hair

    Jens Boos🇨🇦 · Valeri P. Frolov🇨🇦

    We discuss properties of black holes which are pierced by special configurations of cosmic strings. For static black holes we consider radial strings in the limit when the number of strings grows to infinity while the tension of each single string tends to zero. In a properly taken limit the stress-energy tensor of the string distribution is finite. We call such matter stringy matter. We present a solution of the Einstein equations for an electrically charged static black hole with the stringy matter, with and without cosmological constant. This solution is a warped product of two metrics. One of them is a deformed two-sphere whose Gaussian curvature is determined by the energy-density of the stringy matter. We discuss the embedding of a corresponding distorted sphere into a three-dimensional Euclidean space and formulate consistency conditions. We also found a relation between the square of the Weyl tensor invariant of the four dimensional spacetime of the stringy black holes and the energy density of the stringy matter. In the second part of the paper, we discuss test stationary strings in the Kerr geometry and in its Kerr-NUT-(A)dS generalizations. Explicit solutions for strings that are regular at the event horizon are obtained. Using these solutions the stress-energy tensor of the stringy matter in these geometries is calculated. Extraction of the angular momentum from rotating black holes by such strings is also discussed.

    ↳ gr-qchep-phPRD(2018)·9 citations
14. 14*

    Partial restoration of chiral symmetry in cold nuclear matter: the $\varphi$-meson case

    J.J. Cobos-Martínez🇲🇽 · K Tsushima🇧🇷 · G Krein🇧🇷 · A W Thomas🇦🇺

    The work presented at this workshop is divided into two parts. In the first part, the mass and decay width of the $\varphi$-meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $\varphi$-meson self-energy, employing medium-modified kaon masses calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. At normal nuclear matter density, we find a downward shift of the $\varphi$ mass by a few percent, while the decay width is enhanced by an order of magnitude. Our results support the literature which suggest that one should observe a small downward mass shift and a large broadening of the decay width. In the second part, we present $\varphi$-meson--nucleus bound state energies and absorption widths for four selected nuclei, calculated by solving the Klein-Gordon equation with complex optical potentials. The attractive potential for the $\varphi$-meson in the nuclear medium originates from the in-medium enhanced KK loop in the $\varphi$-meson selfenergy. The results suggest that the $\varphi$-meson should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.

    ↳ nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2017)·5 citations
15. 15*

    D-instantons in Real Time Dynamics

    Si-wen Li🇨🇳 · Shu Lin🇨🇳

    Instanton is known to exist in Euclidean spacetime only. Their role in real time dynamics is usually understood as tunneling effect by Wick rotation. We illustrate other effects of instanton in holography by investigating 5d effective gravity theory of the black D3-brane-D-instanton system. The supergravity description of the D3-brane-D-instanton system is dual to the super Yang-Mills theory with topological excitations of the vacuum. We obtain Euclidean correlators in the presence of instantons by analyzing of the fluctuations of the bulk fields in the 5d effective theory. Furthermore, analytic continuation of Euclidean correlators leads to retarded correlators, which characterize real time dynamics. We find interestingly real time fluctuations of topological charge can destroy instantons and the lifetime of instanton is set by temperature. This implies instanton contribution to "real time dynamics" is suppressed at high temperature, which is analogous to classic field theory results that instanton contribution to "thermodynamics" is suppressed at high temperature.

    ↳ hep-thhep-phnucl-thPRD(2018)·8 citations
16. 16*

    A combined dark matter study of AMS-02 antiprotons and Fermi-LAT gamma rays

    Alessandro Cuoco🇩🇪 · Jan Heisig🇩🇪 · Michael Korsmeier🇩🇪 · Michael Krämer🇩🇪

    Observations of cosmic rays are a sensitive probe of dark matter annihilation in our Galaxy. In this article we present an analysis of the AMS-02 antiproton data, reducing cosmic-ray propagation uncertainties by fitting at the same time dark matter and propagation parameters. The result exhibits a possible hint for dark matter pointing to an annihilation cross section close to the thermal value. We investigate the compatibility of this signal with a dark matter interpretation of the Galactic center excess seen in the Fermi-LAT gamma-ray data and discuss implications for dark matter models.

    ↳ astro-ph.HEhep-phPoS(2017)·4 citations
17. 17*

    Reaction rates and transport in neutron stars

    Andreas Schmitt🇬🇧 · Peter Shternin🇷🇺

    Understanding signals from neutron stars requires knowledge about the transport inside the star. We review the transport properties and the underlying reaction rates of dense hadronic and quark matter in the crust and the core of neutron stars and point out open problems and future directions.

    ↳ astro-ph.HEhep-phnucl-thAstrophys.Space Sci.Libr.(2018)·95 citations
18. 18*

    First lattice calculation of the QED corrections to leptonic decay rates

    D. Giusti🇮🇹 · V. Lubicz🇮🇹 · G. Martinelli🇮🇹 · C.T. Sachrajda🇬🇧 · F. Sanfilippo🇮🇹 · S. Simula🇮🇹 · N. Tantalo🇮🇹 · C. Tarantino🇮🇹

    The leading-order electromagnetic and strong isospin-breaking corrections to the ratio of $K_{\mu 2}$ and ${\pi }_{\mu 2}$ decay rates are evaluated for the first time on the lattice, following a method recently proposed. The lattice results are obtained using the gauge ensembles produced by the European Twisted Mass Collaboration with $N_f=2+1+1$ dynamical quarks. Systematics effects are evaluated and the impact of the quenched QED approximation is estimated. Our result for the correction to the tree-level $K_{\mu 2}/{\pi }_{\mu 2}$ decay ratio is $-1.22(16)\%$ to be compared to the estimate $-1.12(21)\%$ based on Chiral Perturbation Theory and adopted by the Particle Data Group.

    ↳ hep-lathep-exhep-phPRL(2018)·122 citations
19. 19*

    Confronting the Potential-driven DBI-inspired nonminimal kinetic coupling (Dinkic) inflation to the observational data

    Jun Chen🇨🇳 · Hou Wenjie🇨🇳 · Defu Hou🇨🇳 · Taotao Qiu🇨🇳

    In the previous work, a new kind of inflation model was proposed, which has the interesting property that its perturbation equation of motion gets a correction of k^4, due to the non-linearity of the kinetic term. Nonetheless, the scale-invariance of the power spectrum remains valid, both in large-k and small-k limits. In this paper, we investigate in detail the spectral index, the index running and the tensor/scalar ratio in this model, especially on the potential-driven case, and compare the results to the current PLANCK/BICEP observational data. We also discuss the tensor spectrum in this case, which is expected to be tested by the future observations on primordial gravitational waves.

    ↳ astro-ph.COgr-qchep-phhep-thCPC(2018)·7 citations
20. 20*

    Causality of fluid dynamics for high-energy nuclear collisions

    Stefan Floerchinger🇩🇪 · Eduardo Grossi🇩🇪

    Dissipative relativistic fluid dynamics is not always causal and can favor superluminal signal propagation under certain circumstances. On the other hand, high-energy nuclear collisions have a microscopic description in terms of QCD and are expected to follow the causality principle of special relativity. We discuss under which conditions the fluid evolutions for a radial expansion are hyperbolic and how the properties of the solutions are encoded in the associated characteristic curves. The expansion dynamics is causal in relativistic sense if the characteristic velocities are smaller than the speed of light. We obtain a concrete inequality from this constraint and discuss how it can be violated for certain initial conditions. We argue that causality poses a bound to the applicability of relativistic fluid dynamics. }

    ↳ nucl-thhep-phJHEP(2018)·45 citations
21. 21*

    Four-point function in general kinematics through geometrical splitting and reduction

    Andrei I. Davydychev🇷🇺

    It is shown how the geometrical splitting of N-point Feynman diagrams can be used to simplify the parametric integrals and reduce the number of variables in the occurring functions. As an example, a calculation of the dimensionally-regulated one-loop four-point function in general kinematics is presented.

    ↳ hep-thhep-phmath-phmath.MPJ.Phys.Conf.Ser.(2018)·19 citations
22. 22*

    Search for flavor-changing interactions of the top quark with the Higgs boson in $H\to b\bar{b}$ channel at $\sqrt{s}=13\mathrm{TeV}$

    Predrag Cirkovic (on behalf of the CMS Collaboration)🇷🇸

    A search for flavor-changing neutral current (FCNC) processes in associated production of a top quark and Higgs boson, with the Higgs boson decaying to a pair of b quarks, is presented. To experimentally probe the top-Higgs FCNC couplings, for the first time the single-top production is considered as a signal process. One isolated lepton and at least three reconstructed jets, among which at least two are identified as b quark jets, are found in the final state. The data sample corresponds to an integrated luminosity of $35.9\mathrm{f}{\mathrm{b}}^{-1}$ recorded by the CMS experiment at the LHC in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ in 2016, and the final results are presented in the form of the observed and expected 95\% CL upper limits on the branching ratio of top quark decays.

    ↳ hep-exhep-ph0 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.