Mon·Mar 13, 2017Monday·March 13, 2017

1. 01*

   Two Higgs Doublet Models and $b\to s$ exclusive decays

   Pere Arnan🇪🇸 · Damir Bečirević🇫🇷 · Federico Mescia🇪🇸 · Olcyr Sumensari🇫🇷

   We computed the leading order Wilson coefficients relevant to all the exclusive $b\to s{\ell }^{+}{\ell }^{-}$ decays in the framework of Two Higgs Doublet Model (2HDM) with a softly broken ${\mathbb{Z}}_2$ symmetry by including the $\mathcal{O}(m_b)$ corrections. We elucidate the issue of appropriate matching between the full and the effective theory when dealing with the (pseudo-)scalar operators for which keeping the external momenta different from zero is necessary. We then make a phenomenological analysis by using the measured $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$ and $\mathcal{B}(B\to K{\mu }^{+}{\mu }^{-}{)}_{\mathrm{high}-q^2}$, for which the hadronic uncertainties are well controlled, and discussed their impact on various types of 2HDM. A brief discussion of the decays with $\tau$-leptons in the final state is also made.

   hep-phEPJC(2017)·74 citations
2. 02*

   Resolving the atmospheric octant by an improved measurement of the reactor angle

   Sabya Sachi Chatterjee🇮🇳 · Pedro Pasquini🇧🇷 · J.W.F. Valle🇪🇸

   Taking into account the current global information on neutrino oscillation parameters we forecast the capabilities of future long baseline experiments such as DUNE and T2HK in settling the atmospheric octant puzzle. We find that a good measurement of the reactor angle ${\theta }_{13}$ plays a key role in fixing the octant of the atmospheric angle ${\theta }_{23}$ with such future accelerator neutrino studies.

   hep-phPRD(2017)·15 citations
3. 03*

   Validity of two Higgs doublet models with a scalar color octet up to a high energy scale

   Li Cheng🇺🇸 · German Valencia🇦🇺

   We have recently studied theoretical constraints on the parameters of a 2HDM augmented with a color-octet scalar. In this paper we consider the consequences of requiring the model to remain valid up to very high energy scales, such as the GUT scale. The acceptable region of parameter space is reduced when one insists on vacuum stability, perturbative unitarity and the absence of Landau poles below a given scale. As the scale to which we require the model to be valid is increased, the acceptable region of parameter space for the 2HDM sector is reduced in such a way that it approaches the alignment limit, $\cos (\beta -\alpha )\to 0$, and the masses of $H^0$, $A$ and $H^{\pm }$ are pushed closer to each other. The parameters of the color octet sector are also restricted to an increasingly smaller region.

   hep-phPRD(2017)·8 citations
4. 04*

   A precise determination of the top-quark pole mass

   Sheng-Quan Wang🇨🇳 · Xing-Gang Wu🇨🇳 · Zong-Guo Si🇨🇳 · Stanley J. Brodsky🇺🇸

   The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate the renormalization scheme and renormalization scale uncertainties for high-energy processes. We have observed that by applying PMC scale-setting, one obtains comprehensive and self-consistent pQCD predictions for the top-quark pair total cross-section and the top-quark pair forward-backward asymmetry in agreement with the measurements at the Tevatron and LHC. As a step forward, in the present paper, we determine the top-quark pole mass via a detailed comparison of the top-quark pair cross-section with the measurements at the Tevatron and LHC. The results for the top-quark pole mass are $m_t=174.6_{-3.2}^{+3.1}$ GeV for the Tevatron with $\sqrt{S}=1.96$ TeV, $m_t=173.7\pm 1.5$ GeV and $174.2\pm 1.7$ GeV for the LHC with $\sqrt{S}=7$ TeV and $8$ TeV, respectively. Those predictions agree with the average, $173.34\pm 0.76$ GeV, obtained from various collaborations via direct measurements. The consistency of the pQCD predictions using the PMC with all of the collider measurements at different energies provides an important verification of QCD.

   hep-phEPJC(2018)·16 citations
5. 05*

   Understanding forward $B$ hadron production

   Rhorry Gauld🇨🇭

   The LHCb collaboration has recently performed a measurement of the production rate of inclusive $B$ hadron production ($pp\to BX$) at both 7 and 13~TeV centre-of-mass (CoM) energies. As part of this measurement, the ratio of these two cross section measurements has been presented differentially in $B$ hadron pseudorapidity within the range of ${\eta }_B\in [2.0,5.0]$. A large tension ($4\sigma$) is observed for the ratio measurement in the lower pseudorapidity range of ${\eta }_B\in [2.0,3.0]$, where the data is observed to exceed theoretical predictions, while consistency is found at larger ${\eta }_B$ values. This behaviour is not expected within perturbative QCD, and can only be achieved by introducing ad-hoc features into the structure of the non-perturbative gluon PDF within the region of $x\in [10^{-3},10^{-4}]$. Specifically, the gluon PDF must grow extremely quickly with decreasing $x$ within this kinematic range, closely followed by a period of decelerated growth. However, such behaviour is highly disfavoured by global fits to proton structure. Further studies of the available LHCb $B$ and $D$ hadron cross section data, available for a range of CoM energies, indicate systematic tension in the (pseudo)rapidity region of $[2.0,2.5]$.

   hep-phhep-exJHEP(2017)·10 citations
6. 06*

   Charged-Higgs on $R_{D^{(\ast )}}$, $\tau$ polarization, and FBA

   Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇹🇼

   We study the influence of a charged-Higgs on the excess of branching fraction ratio, $R_M=BR(\bar{B}\to M\tau {\bar{\nu }}_{\tau })/BR(\bar{B}\to M\ell {\bar{\nu }}_{\ell })$ $(M=D,D^{\ast })$, in a generic two-Higgs-doublet model. In order to investigate the lepton polarization, the detailed decay amplitudes with lepton helicity are given. When the charged-Higgs is used to resolve excesses, it is found that two independent Yukawa couplings are needed to explain the $R_D$ and $R_{D^{\ast }}$ anomalies. We show that when the upper limit of $BR(B_c\to \tau {\bar{\nu }}_{\tau })<30\%$ is included, $R_D$ can be significantly enhanced while $R_{D^{\ast }}<0.27$. With the $BR(B_c\to \tau {\bar{\nu }}_{\tau })$ constraint, we find that the $\tau$-lepton polarizations can be still affected by the charged-Higgs effects, where the standard model (SM) predictions are obtained as: $P_D^{\tau }\approx 0.324$ and $P_{D^{\ast }}^{\tau }\approx -0.500$, and they can be enhanced to be $P_D^{\tau }\approx 0.5$ and $P_{D^{\ast }}^{\tau }\approx -0.41$ by the charged-Higgs. The integrated lepton froward-backward asymmetry (FBA) is also studied, where the SM result is ${\bar{A}}_{FB}^{D^{(\ast )},\tau }\approx -0.359(0.064)$, and they can be enhanced (decreased) to be ${\bar{A}}_{FB}^{D^{(\ast )},\tau }\approx -0.33(0.02)$.

   hep-phhep-exEPJC(2017)·47 citations
7. 07*

   CP as a Symmetry of Symmetries

   Andreas Trautner🇩🇪

   It is explained that the Standard Model combined charge conjugation and parity transformation (CP) is a simultaneous complex conjugation outer automorphism transformation of gauge and space-time symmetries. Simple examples are given for the general concept of outer automorphisms ("symmetries of symmetries"), as well as for their possible actions on physical theories. It is highlighted that complex conjugation outer automorphisms do not, in general, exist for all symmetries. Examples are given for cases in which the physical CP transformation is violated as a consequence of requiring another symmetry. A toy model is illustrated in which CP is spontaneously violated in the broken phase of a continuous gauge symmetry, while an unbroken outer automorphism protects the topological vacuum angle at $\theta =0$.

   hep-phJ.Phys.Conf.Ser.(2017)·5 citations
8. 08*

   Version 3 of {\tt RunDec} and {\tt CRunDec}

   Florian Herren🇩🇪 · Matthias Steinhauser🇩🇪

   We present new versions of the packages {\tt RunDec} and {\tt CRunDec} which can be used for the running and decoupling of the strong coupling constant and quark masses. Furthermore several conversion formulae for heavy quark masses are implemented. The new versions include five-loop corrections of the QCD beta function and four-loop decoupling effects. Furthermore, various relations between the heavy quark mass defined in the $\overline{\mathrm{MS}}$ and other short-distance schemes are implemented to next-to-next-to-next-to-leading order. We discuss in detail the improvements and provide several examples which show how {\tt RunDec} and {\tt CRunDec} can be used in frequently occurring situations.

   hep-phComput.Phys.Commun.(2018)·355 citations
9. 09*

   Controlled Flavour Changing Neutral Couplings in Two Higgs Doublet Models

   Joao M. Alves (Lisbon, IST)🇵🇹 · Francisco J. Botella (Valencia U., IFIC & Valencia U.)🇪🇸 · Gustavo C. Branco (Lisbon, CFTP & Lisbon, IST)🇵🇹 · Fernando Cornet-Gomez (Valencia U., IFIC & Valencia U.)🇪🇸 · Miguel Nebot (Lisbon, CFTP & Lisbon, IST)🇵🇹

   We propose a class of Two Higgs Doublet Models where there are Flavour Changing Neutral Currents (FCNC) at tree level, but under control due to the introduction of a discrete symmetry in the full Lagrangian. It is shown that in this class of models, one can have simultaneously FCNC in the up and down sectors, in contrast to the situation encountered in BGL models. The intensity of FCNC is analysed and it is shown that in this class of models one can respect all the strong constraints from experiment without unnatural fine-tuning. It is pointed out that the additional sources of flavour and CP violation are such that they can enhance significantly the generation of the Baryon Asymmetry of the Universe, with respect to the Standard Model.

   hep-phhep-exEPJC(2017)·30 citations
10. 10*

    Naturalizing Gravity of the Quantum Fields, and the Hierarchy Problem

    Durmus Demir🇹🇷

    It is shown that gravity can be incorporated into the Standard Model (SM) in a way solving the hierarchy problem. For this, the SM effective action in flat spacetime is adapted to curved spacetime via not only the general covariance but also the gauge invariance. For the latter, gauge field hard masses, induced by loops at the UV scale $\Lambda$, are dispelled by construing $\Lambda$ as the constant value assigned to curvature. This gives way to an unprecedented mechanism for incorporating gravity into the SM in that the hierarchy problem is solved by transmutation of the Higgs boson ${\Lambda }^2$--mass into the Higgs-curvature coupling, and the cosmological constant problem is alleviated by metamorphosis of the vacuum ${\Lambda }^4$--energy into the Einstein-Hilbert term. Gravity emerges correctly if the SM is accompanied by a secluded dark sector sourcing non-interacting dark matter, dark energy and dark radiation. Physics beyond the SM, containing Higgs-phobic scalars that resolve the strong CP problem, flavor problem, baryogenesis and inflation, respects the hierarchy. Majorana neutrinos are naturally incorporated if $\Lambda$ lies at the see-saw scale. This mechanism, in general, leaves no compelling reason to anticipate new particles at the LHC or higher-energy colliders.

    hep-phgr-qchep-th10 citations
11. 11*

    Strong Bayesian Evidence for the Normal Neutrino Hierarchy

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

    The configuration of the three neutrino masses can take two forms, known as the normal and inverted hierarchies. We compute the Bayesian evidence associated with these two hierarchies. Previous studies found a mild preference for the normal hierarchy, and this was driven by the asymmetric manner in which cosmological data has confined the available parameter space. Here we identify the presence of a second asymmetry, which is imposed by data from neutrino oscillations. By combining constraints on the squared-mass splittings with the limit on the sum of neutrino masses of $\Sigma m_{\nu }<0.13$ eV, and using a minimally informative prior on the masses, we infer odds of 42:1 in favour of the normal hierarchy, which is classified as "strong" in the Jeffreys' scale. We explore how these odds may evolve in light of higher precision cosmological data, and discuss the implications of this finding with regards to the nature of neutrinos. Finally the individual masses are inferred to be $m_1=3.80_{-3.73}^{+26.2}\text{meV},m_2=8.8_{-1.2}^{+18}\text{meV},m_3=50.4_{-1.2}^{+5.8}\text{meV}$ ($95\%$ credible intervals).

    ↳ astro-ph.COhep-phJCAP(2017)·90 citations
12. 12*

    Charge asymmetry measurements in $t\bar{t}$ events at the LHC

    Mohsen Naseri🇮🇷

    An overview of the most recent measurements on top quark charge asymmetry in top quark pair production is presented. The results are obtained using data collected with ATLAS and CMS detectors in proton-proton collisions at centre-of-mass energies of 8 TeV. In these studies, either dileptonic or semileptonic top pair decays are analyzed. All measurements are comparable with the standard model prediction and no sign of new physics is observed.

    ↳ hep-exhep-ph1 citation
13. 13*

    In-medium viscous coefficients of a hot hadronic gas mixture

    Utsab Gangopadhyaya🇮🇳 · Snigdha Ghosh🇮🇳 · Sukanya Mitra🇮🇳 · Sourav Sarkar🇮🇳

    We estimate the shear and the bulk viscous coefficients for a hot hadronic gas mixture constituting of pions and nucleons. The viscosities are evaluated in the relativistic kinetic theory approach by solving the transport equation in the relaxation time approximation for binary collisions ($\pi \pi$,$\pi N$ and $NN$). Instead of vacuum cross-sections usually used in the literature we employ in-medium scattering amplitudes in the estimation of the relaxation times. The modified cross-sections for $\pi \pi$ and $\pi N$ scattering are obtained using one-loop modified thermal propagators for $\rho$, $\sigma$ and $\Delta$ in the scattering amplitudes which are calculated using effective interactions. The resulting suppression of the cross sections at finite temperature and baryon density is observed to significantly affect the $T$ and ${\mu }_N$ dependence of the viscosities of the system.

    ↳ nucl-thhep-phPRC(2016)·15 citations
14. 14*

    Nonlinear resonant oscillation of gravitational potential induced by ultralight axion in $f(R)$ gravity

    Arata Aoki🇯🇵 · Jiro Soda🇯🇵

    We study the ultralight axion dark matter with mass around $10^{-22}$ eV in $f(R)$ gravity which might resolve the dark energy problem. In particular, we focus on the fact that the pressure of the axion field oscillating in time produces oscillations of gravitational potentials. We show that the oscillation of the gravitational potential is sensitive to the model of gravity. Remarkably, we find that the detectability of the oscillation through the gravitational wave detectors can be significantly enhanced due to the nonlinear resonance between the ultralight axion and the scalaron.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2017)·20 citations
15. 15*

    Density of States FFA analysis of SU(3) lattice gauge theory at a finite density of color sources

    Mario Giuliani🇦🇹 · Christof Gattringer🇦🇹

    We present a Density of States calculation with the Functional Fit Approach (DoS FFA) in SU(3) lattice gauge theory with a finite density of static color sources. The DoS FFA uses a parameterized density of states and determines the parameters of the density by fitting data from restricted Monte Carlo simulations with an analytically known function. We discuss the implementation of DoS FFA and the results for a qualitative picture of the phase diagram in a model which is a further step towards implementing DoS FFA in full QCD. We determine the curvature $\kappa$ in the $\mu$-$T$ phase diagram and find a value close to the results published for full QCD.

    ↳ hep-lathep-phPLB(2017)·20 citations
16. 16*

    Exotic Compact Objects and How to Quench their Ergoregion Instability

    Elisa Maggio🇮🇹 · Paolo Pani🇮🇹 · Valeria Ferrari🇮🇹

    Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some quantum-gravity models of exotic compact objects. A generic feature of these models is the replacement of the horizon by a reflective surface. Objects with these properties are prone to the so-called ergoregion instability when they spin sufficiently fast. We investigate in detail a simple model consisting of scalar perturbations of a Kerr geometry with a reflective surface near the horizon. The instability depends on the spin, on the compactness, and on the reflectivity at the surface. The instability time scale increases only logarithmically in the black-hole limit and, for a perfectly reflecting object, this is not enough to prevent the instability from occurring on dynamical time scales. However, we find that an absorption rate at the surface as small as 0.4% (reflectivity coefficient as large as $|\mathcal{R}{|}^2=0.996$) is sufficient to quench the instability completely. Our results suggest that exotic compact objects are not necessarily ruled out by the ergoregion instability.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2017)·142 citations
17. 17*

    Heavy-ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell-Yan Production

    B. Trzeciak🇳🇱 · C. Da Silva🇺🇸 · E.G. Ferreiro🇪🇸 · C. Hadjidakis🇫🇷 · D. Kikola🇵🇱 · J.P. Lansberg🇫🇷 · L. Massacrier🇫🇷 · J. Seixas🇵🇹 · A. Uras🇫🇷 · Z. Yang🇨🇳

    We outline the case for heavy-ion-physics studies using the multi-TeV lead LHC beams in the fixed-target mode. After a brief contextual reminder, we detail the possible contributions of AFTER@LHC to heavy-ion physics with a specific emphasis on quarkonia. We then present performance simulations for a selection of observables. These show that ${\rm Y}(nS)$, $J/\psi$ and $\psi (2S)$ production in heavy-ion collisions can be studied in new energy and rapidity domains with the LHCb and ALICE detectors. We also discuss the relevance to analyse the Drell-Yan pair production in asymmetric nucleus-nucleus collisions to study the factorisation of the nuclear modification of partonic densities and of further quarkonia to restore their status of golden probes of the quark-gluon plasma formation.

    ↳ nucl-exhep-exhep-phnucl-thFew Body Syst.(2017)·19 citations
18. 18*

    The R*-operation for Feynman graphs with generic numerators

    Franz Herzog🇳🇱 · Ben Ruijl🇳🇱

    The R*-operation by Chetyrkin, Tkachov, and Smirnov is a generalisation of the BPHZ R-operation, which subtracts both ultraviolet and infrared divergences of euclidean Feynman graphs with non-exceptional external momenta. It can be used to compute the divergent parts of such Feynman graphs from products of simpler Feynman graphs of lower loops. In this paper we extend the R*-operation to Feynman graphs with arbitrary numerators, including tensors. We also provide a novel way of defining infrared counterterms which closely resembles the definition of its ultraviolet counterpart. We further express both infrared and ultraviolet counterterms in terms of scaleless vacuum graphs with a logarithmic degree of divergence. By exploiting symmetries, integrand and integral relations, which the counterterms of scaleless vacuum graphs satisfy, we can vastly reduce their number and complexity. A FORM implementation of this method was used to compute the five loop beta function in QCD for a general gauge group. To illustrate the procedure, we compute the poles in the dimensional regulator of all top-level propagator graphs at five loops in four dimensional phi^3 theory.

    ↳ hep-thhep-phJHEP(2017)·75 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.