Wed·Jul 5, 2017Wednesday·July 5, 2017

1. 01*

   On Dark Matter Interactions with the Standard Model through an Anomalous $Z^{\prime }$

   Ahmed Ismail🇺🇸 · Andrey Katz🇨🇭 · Davide Racco🇨🇭

   We study electroweak scale Dark Matter (DM) whose interactions with baryonic matter are mediated by a heavy anomalous $Z^{\prime }$. We emphasize that when the DM is a Majorana particle, its low-velocity annihilations are dominated by loop suppressed annihilations into the gauge bosons, rather than by p-wave or chirally suppressed annihilations into the SM fermions. Because the $Z^{\prime }$ is anomalous, these kinds of DM models can be realized only as effective field theories (EFTs) with a well-defined cutoff, where heavy spectator fermions restore gauge invariance at high energies. We formulate these EFTs, estimate their cutoff and properly take into account the effect of the Chern-Simons terms one obtains after the spectator fermions are integrated out. We find that, while for light DM collider and direct detection experiments usually provide the strongest bounds, the bounds at higher masses are heavily dominated by indirect detection experiments, due to strong annihilation into $W^{+}{W}^{-}$, $ZZ$, $Z\gamma$ and possibly into $gg$ and $\gamma \gamma$. We emphasize that these annihilation channels are generically significant because of the structure of the EFT, and therefore these models are prone to strong indirect detection constraints. Even though we focus on selected $Z^{\prime }$ models for illustrative purposes, our setup is completely generic and can be used for analyzing the predictions of any anomalous $Z^{\prime }$-mediated DM model with arbitrary charges.

   hep-phastro-ph.COastro-ph.HEJHEP(2017)·35 citations
2. 02*

   Higher dimensional operators in 2HDM

   Siddhartha Karmakar🇮🇳 · Subhendu Rakshit🇮🇳

   We present a complete (non-redundant) basis of CP- and flavour-conserving six-dimensional operators in a two Higgs doublet model (2HDM). We include Z_2-violating operators as well. In such a 2HDM effective field theory (2HDMEFT), we estimate how constraining the 2HDM parameter space from experiments can get disturbed due to these operators. Our basis is motivated by the strongly interacting light Higgs (SILH) basis used in the standard model effective field theory (SMEFT). We find out bounds on combinations of Wilson coefficients of such operators from precision observables, signal strengths of Higgs decaying into vector bosons etc. In 2HDMEFT, the 2HDM parameter space can play a significant role while deriving such constraints, by leading to reduced or even enhanced effects compared to SMEFT in certain processes. We also comment on the implications of the SILH suppressions in such considerations.

   hep-phhep-thJHEP(2017)·22 citations
3. 03*

   MeV Dark Matter: Model Independent Bounds

   Enrico Bertuzzo🇧🇷 · Cristian J. Caniu Barros🇧🇷 · Giovanni Grilli di Cortona🇧🇷

   We use the framework of dark matter effective field theories to study the complementarity of bounds for a dark matter particle with mass in the MeV range. Taking properly into account the mixing between operators induced by the renormalization group running, we impose experimental constraints coming from the CMB, BBN, LHC, LEP, direct detection experiments and meson decays. In particular, we focus on the case of a vector coupling between the dark matter and the standard model fermions, and study to which extent future experiments can hope to probe regions of parameters space which are not already ruled out by current data.

   hep-phJHEP(2017)·48 citations
4. 04*

   Expectations for the muon g-2 in simplified models with dark matter

   Kamila Kowalska🇩🇪 · Enrico Maria Sessolo🇵🇱

   We investigate simplified models of new physics that can accommodate the measured value of the anomalous magnetic moment of the muon and the relic density of dark matter. We define a set of renormalizable, SU(2)$\times$U(1) invariant extensions of the Standard Model, each comprising an inert $Z_2$-odd scalar field and one or more vector-like pairs of colorless fermions that communicate to the muons through Yukawa-type interactions. The new sectors are classified according to their transformation properties under the Standard Model gauge group and all models are systematically confronted with a variety of experimental constraints: LEP mass bounds, direct LHC searches, electroweak precision observables, and direct searches for dark matter. We show that scenarios featuring only one type of new fermions become very predictive once the relic density and collider constraints are taken into account, as in this case $g-2$ is not enhanced by chirality flip. Conversely, for models where an additional source of chiral-symmetry violation is generated via fermion mixing, the constraints are much looser and new precision experiments with highly suppressed systematic uncertainties may be required to test the parameter space.

   hep-phJHEP(2017)·110 citations
5. 05*

   Shear Viscosity of Quark-Gluon Plasma in Weak Magnetic Field in Perturbative QCD: Leading Log

   Shiyong Li🇺🇸 · Ho-Ung Yee🇺🇸

   We compute the shear viscosity of two-flavor QCD plasma in an external magnetic field in perturbative QCD at leading log order, assuming that the magnetic field is weak or soft: $eB\sim g^4\log (1/g)T^2$. We show that the shear viscosity takes a form $\eta =\bar{\eta }(\bar{B})T^3/(g^4\log (1/g))$ with a dimensionless function $\bar{\eta }(\bar{B})$ in terms of a dimensionless variable $\bar{B}=(eB)/(g^4\log (1/g)T^2)$. The variable $\bar{B}$ corresponds to the relative strength of the effect of cyclotron motions compared to the QCD collisions: $\bar{B}\sim l_{mfp}/l_{cyclo}$. We provide a full numerical result for the scaled shear viscosity $\bar{\eta }(\bar{B})$.

   hep-phnucl-thPRD(2018)·64 citations
6. 06*

   A viable D-term hybrid inflation

   Kenji Kadota🇰🇷 · Tatsuo Kobayashi🇯🇵 · Keigo Sumita🇯🇵

   We propose a new model of the D-term hybrid inflation in the framework of supergravity. Although our model introduces, analogously to the conventional D-term inflation, the inflaton and a pair of scalar fields charged under a $U(1)$ gauge symmetry, we study the logarithmic and exponential dependence on the inflaton field, respectively, for the Kähler and superpotential. This results in a characteristic one-loop scalar potential consisting of linear and exponential terms, which realizes the small-field inflation dominated by the Fayet-Iliopoulos term. With the reasonable values for the coupling coefficients and, in particular, with the $U(1)$ gauge coupling constant comparable to that of the Standard Model, our D-term inflation model can solve the notorious problems in the conventional D-term inflation, namely, the CMB constraints on the spectral index and the generation of cosmic strings.

   hep-phastro-ph.COhep-thJCAP(2017)·4 citations
7. 07*

   Leptogenesis and composite heavy neutrinos with gauge mediated interactions

   Simone Biondini🇨🇭 · Orlando Panella🇮🇹

   Leptogenesis is an appealing framework to account for the baryon asymmetry in the universe. To this end physics beyond the Standard Model is demanded. In this paper we investigate the possibility to attain successful leptogenesis with composite Majorana neutrinos. We work in the framework of effective gauge mediated and contact interactions without any reference to an underlying compositeness theory. This approach is the one adopted in all current experimental searches for composite fermions at colliders. In the case of gauge mediated interactions, we calculate the CP asymmetry in heavy composite neutrino decays. Both the direct and indirect CP asymmetry are derived and resonant leptogenesis is also discussed. We find that the Sakharov conditions can be met and, for some choice of the parameters, the correct order of magnitude of the baryon asymmetry is reproduced.

   hep-phEPJC(2017)·12 citations
8. 08*

   Parton distribution functions with QED corrections in the valon model

   Marzieh Mottaghizadeh🇮🇷 · Fatemeh Taghavi Shahri🇮🇷 · Parvin Eslami🇮🇷

   Parton distribution functions (PDFs) with QED corrections extracted from the QED$\otimes$QCD DGLAP evolution equations in the framework of "valon" model. Our results for the PDFs with QED corrections in this phenomenological model are in good agreement with the newly related CT14QED global fit code [Phys. Rev. D93, 114015 (2016)] and APFEL (NNPDF2.3QED) [Computer Physics Communications 185, 1647 (2014)] program in a wide range of $x=[10^{-5},1]$ and $Q^2=[0.283,10^8]{\mathrm{GeV}}^2$. The model calculations agree rather well with those codes. We also proposed the new method for studying the symmetry breaking of the sea quarks distribution functions inside proton. Then these PDFs set can be used to explore the proton-proton scattering at the LHC era.

   hep-phPRD(2017)·5 citations
9. 09*

   Do metric fluctuations affect the Higgs dynamics during inflation?

   Tommi Markkanen🇬🇧 · Sami Nurmi🇫🇮 · Arttu Rajantie🇬🇧

   We show that the dynamics of the Higgs field during inflation is not affected by metric fluctuations if the Higgs is an energetically subdominant light spectator. For Standard Model parameters we find that couplings between Higgs and metric fluctuations are suppressed by $\mathcal{O}(10^{-7})$. They are negligible compared to both pure Higgs terms in the effective potential and the unavoidable non-minimal Higgs coupling to background scalar curvature. The question of the electroweak vacuum instability during high energy scale inflation can therefore be studied consistently using the Jordan frame action in a Friedmann--Lemaître--Robertson--Walker metric, where the Higgs-curvature coupling enters as an effective mass contribution. Similar results apply for other light spectator scalar fields during inflation.

   hep-phastro-ph.COgr-qcJCAP(2017)·16 citations
10. 10*

    Implications of right-handed neutrinos in $B-L$ extended standard model with scalar dark matter

    Priyotosh Bandyopadhyay🇮🇳 · Eung Jin Chun🇰🇷 · Rusa Mandal🇮🇳

    We investigate the Standard Model (SM) with a $U(1{)}_{B-L}$ gauge extension where a $B-L$ charged scalar is a viable dark matter (DM) candidate. The dominant annihilation process, for the DM particle is through the $B-L$ symmetry breaking scalar to right-handed neutrino pair. We exploit the effect of decay and inverse decay of the right-handed neutrino in thermal relic abundance of the DM. Depending on the values of the decay rate, the DM relic density can be significantly different from what is obtained in the standard calculation assuming the right-handed neutrino is in thermal equilibrium and there appear different regions of the parameter space satisfying the observed DM relic density. For a DM mass less than $\mathcal{O}$(TeV), the direct detection experiments impose a competitive bound on the mass of the $U(1{)}_{B-L}$ gauge boson $Z^{\prime }$ with the collider experiments. Utilizing the non-observation of the displaced vertices arising from the right-handed neutrino decays, bound on the mass of $Z^{\prime }$ has been obtained at present and higher luminosities at the LHC with 14 TeV centre of mass energy where an integrated luminosity of 100fb${}^{-1}$ is sufficient to probe $m_{Z^{\prime }}\sim 5.5$ TeV.

    hep-phastro-ph.COhep-exPRD(2018)·39 citations
11. 11*

    Framework for evolution in double parton scattering

    M.G.A. Buffing🇩🇪

    Double parton scattering (DPS) describes two colliding hadrons having interactions in the form of two hard processes, each initiated by a separate pair of partons. Just as for single parton scattering, the resummation of soft gluon exchange gives rise to a soft function, which is a necessary ingredient for obtaining rapidity evolution equations. For various regions of phase space, we derive the rapidity evolution and the scale evolution of double transverse momentum dependent parton distribution functions (DTMDs) as well as of the $p_T$-resummed cross section for double Drell-Yan like processes. This contributes to a framework that can be used for phenomenological DPS studies including resummation.

    hep-phPoS(2018)·1 citation
12. 12*

    Collins azimuthal asymmetries of hadron production inside jets

    Zhong-Bo Kang🇺🇸 · Alexei Prokudin🇺🇸 · Felix Ringer🇺🇸 · Feng Yuan🇺🇸

    We investigate the Collins azimuthal asymmetry of hadrons produced inside jets in transversely polarized proton-proton collisions. Recently, the quark transversity distributions and the Collins fragmentation functions have been extracted within global analyses from data of the processes semi-inclusive deep inelastic scattering and electron-positron annihilation. We calculate the Collins azimuthal asymmetry for charged pions inside jets using these extractions for RHIC kinematics at center-of-mass energies of 200 and 500 GeV. We compare our results with recent data from the STAR Collaboration at RHIC and find good agreement, which confirms the universality of the Collins fragmentation functions. In addition, we further explore the impact of transverse momentum dependent evolution effects.

    hep-phhep-exPLB(2017)·73 citations
13. 13*

    Testing the universality of the Collins function in pion-jet production at RHIC

    Umberto D'Alesio🇮🇹 · Francesco Murgia🇮🇹 · Cristian Pisano🇮🇹

    By adopting a generalised parton model approach at leading order in QCD, including spin and intrinsic parton motion effects, we study the Collins azimuthal asymmetries for pions within a large-$p_T$ jet produced at mid-rapidity in polarised hadronic collisions. Using available information on the quark transversity distributions and the pion Collins functions, as extracted from semi-inclusive deeply inelastic scattering and $e^{+}{e}^{-}\to h_1{h}_{2}X$ processes, we compute estimates for the Collins asymmetries in kinematical configurations presently investigated at RHIC by the STAR Collaboration. Collins-like asymmetries, involving linearly polarised gluons, are also considered. Our predictions, compared against available preliminary data, show a very good agreement, even if some discrepancies, to be further scrutinized both theoretically and experimentally, appear in the transverse momentum dependence of the Collins asymmetry. These results are in favour of the predicted universality of the Collins function and of a mild, if any, evolution with the hard scale of the asymmetries.

    hep-phPLB(2017)·32 citations
14. 14*

    Diphoton Resonances at the LHC

    Emiliano Molinaro🇩🇰 · Natascia Vignaroli🇩🇰

    We review the current status of searches for new physics beyond the Standard Model in the diphoton channel at the LHC and estimate the reach with future collected data. We perform a model independent analysis based on an effective field theory approach and different production mechanisms. As an illustrative example, we apply our results to a scenario of minimal composite dynamics.

    hep-phhep-exMod.Phys.Lett.A(2017)·7 citations
15. 15*

    Minimal realization of right-handed gauge symmetry

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼

    We propose a minimally extended gauge symmetry model with $U(1{)}_R$, where only the right-handed fermions have nonzero charges in the fermion sector. To achieve both anomaly cancellations and minimality, three right-handed neutrinos are naturally required, and the standard model Higgs has to have nonzero charge under this symmetry. Then we find that its breaking scale($\Lambda$) is restricted by precise measurement of neutral gauge boson in the standard model; therefore, $\mathcal{O}$(10) TeV$\lesssim \Lambda$. We also discuss its testability of the new gauge boson and discrimination of $U(1{)}_R$ model from $U(1{)}_{B-L}$ one at collider physics such as LHC and ILC.

    hep-phhep-exPRD(2018)·23 citations
16. 16*

    Two loop virtual corrections to $b\to (d,s){\ell }^{+}{\ell }^{-}$ and $c\to u{\ell }^{+}{\ell }^{-}$ for arbitrary momentum transfer

    Stefan de Boer🇩🇪

    Non-factorizable two loop corrections to heavy to light flavor changing neutral current transitions due to matrix elements of current-current operators are calculated analytically for arbitrary momentum transfer. This extends previous works on $b\to (d,s){\ell }^{+}{\ell }^{-}$ transitions. New results for $c\to u{\ell }^{+}{\ell }^{-}$ transitions are presented. Recent works on polylogarithms are used for the master integrals. For $b\to s{\ell }^{+}{\ell }^{-}$ transitions, the corrections are most significant for the imaginary parts of the effective Wilson coefficients in the large hadronic recoil range. Analytical results and ready-to-use fitted results for a specific set of parameters are provided.

    hep-phEPJC(2017)·26 citations
17. 17*

    Full NLO electroweak corrections to Z-boson pair production at the Large Hadron Collider

    Benedikt Biedermann🇩🇪

    We report on a recent calculation of the full next-to-leading-order electroweak corrections to Z-boson pair production with subsequent decays into four charged leptons. Using the complete matrix elements at leading order and next-to-leading order in the electroweak coupling for the processes $pp\to {\mu }^{+}{\mu }^{-}{e}^{+}{e}^{-}$ and $pp\to {\mu }^{+}{\mu }^{-}{\mu }^{+}{\mu }^{-}$, this includes all off-shell effects of intermediate massive vector bosons and photons. We employ a gauge-invariant splitting for the electroweak corrections into purely weak and photonic corrections. The latter show the well-known radiative tails near kinematical thresholds or resonances. The former are generically at the level of $\sim -5\%$ for the fiducial cross section and reach several $-10\%$ in the high-energy tails of distributions due to logarithms of electroweak origin. The impact of interference effects due to equal-flavour leptons in the final state can reach the order of $5\%$ in off-shell-sensitive regions. Photon-induced contributions are included in our calculation, but turn out to be phenomenologically unimportant.

    hep-phPoS(2018)·2 citations
18. 18*

    A new method for evaluating scalar one-loop Feynman integrals in general space-time dimension

    Khiem Hong Phan🇻🇳

    In this paper, we propose a new method for evaluating scalar one-loop Feynman integrals in generalized D-dimension. The calculations play an important building block for two-loop and higher-loop corrections to the processes at future colliders such as the Large Hadron Collider (LHC) and the International Linear Collider (ILC). In this method, scalar one-loop N-point functions will be presented as the one-fold Mellin-Barnes representation of (N-1)-point ones with shifting space-time dimension. This representation offers a clear advantage that we can construct recursively the analytic expressions for N-point functions from the basic ones which are one-point functions. The compact formulae for scalar one-loop two-point functions with massive internal lines and three-point, four-point functions with massless internal lines are given as examples in this article. In particular, they are written in terms of generalized hypergeometric series such as Gauss, Appell F 1 functions. We also perform a sample numerical check for the analytical expressions in this report by comparing with LoopTools and AMBRE/MB. We find that the numerical results from this work are in good agreement with LoopTools at ${ϵ}^0$ -expansion and AMBRE/MB at higher-order of $ϵ$-expansion, at higher D-dimension.

    hep-ph0 citations
19. 19*

    On Higgs decays to hadrons and the R-ratio at N^4LO

    F. Herzog🇳🇱 · B. Ruijl🇳🇱 · T. Ueda🇳🇱 · J.A.M. Vermaseren (1)🇳🇱 · A. Vogt (2)((1) NIHKEF (2) Liverpool U.)🇬🇧

    We present the first determination of Higgs-boson decay to hadrons at the next-to-next-to-next-to-next-to-leading order of perturbative QCD in the limit of a heavy top quark and massless light flavours. This result has been obtained by computing the absorptive parts of the relevant five-loop self-energy for a general gauge group and combining the outcome with the corresponding coefficient function already known to this order in QCD. Our new result reduces the uncertainty due to the truncation of the perturbation series to a fraction of the uncertainty due to the present error of the strong coupling constant. We have also performed the corresponding but technically simpler computations for direct Higgs decay to bottom quarks and for the electromagnetic R-ratio in e^+ e^- -> hadrons, thus verifying important fifth-order results obtained so far only by one group.

    hep-phJHEP(2017)·139 citations
20. 20*

    Inflation scenario driven by a low energy physics inflaton

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

    It is a longstanding desire of cosmologists, and particle physicists as well, to connect inflation to low energy physics, culminating, for instance, in what is known as Higgs inflation. The condition for the standard Higgs boson playing the role of the inflaton, and driving successfully inflation, is that it couples nonminimally with gravity. Nevertheless, cosmological constraints impose that the nonminimal coupling be large. This causes the loss of perturbative unitarity in a scale of energy far below the Planck one. Our aim in this work is to point out that inflaton potential containing a particular type of trilinear coupling involving the inflaton may circumvent this problem by realizing Higgs inflation with tiny nonminimal coupling of the inflaton with gravity. We then develop the idea within a toy model and implement it in the inverse type-II seesaw mechanism for small neutrinos masses.

    hep-phPRD(2017)·17 citations
21. 21*

    Broadening the Reach of Simplified Limits on Resonances at the LHC

    R. Sekhar Chivukula🇺🇸 · Pawin Ittisamai🇹🇭 · Kirtimaan Mohan🇺🇸 · Elizabeth H. Simmons🇺🇸

    Recently, we introduced an approach for more easily interpreting searches for resonances at the LHC - and to aid in distinguishing between realistic and unrealistic alternatives for potential signals. This `simplfied limits' approach was derived using the narrow width approximation (NWA) - and therefore was not obviously relevant in the case of wider resonances. Here, we broaden the scope of the analysis. First, we explicitly generalize the formalism to encompass resonances of finite width. We then examine how the width of the resonance modifies bounds on new resonances that are extracted from LHC searches. Second, we demonstrate, using a wide variety of cases, with different incoming partons, resonance properties, and decay signatures, that the limits derived in the NWA yield pertinant, and somewhat conservative (less stringent) bounds on the model parameters. We conclude that the original simplified limits approach is useful in the early stages of evaluating and interpreting new collider data and that the generalized approach is a valuable further aid when evidence points toward a broader resonance.

    hep-phhep-exPRD(2017)·9 citations
22. 22*

    Absolute Lower Bound on the Bounce Action

    Ryosuke Sato🇮🇱 · Masahiro Takimoto🇯🇵

    The decay rate of a false vacuum is determined by the minimal action solution of the tunnelling field: bounce. In this Letter, we focus on models with scalar fields which have a canonical kinetic term in $N(>2)$ dimensional Euclidean space, and derive an absolute lower bound on the bounce action. In the case of four-dimensional space, we show the bounce action is generically larger than $24/{\lambda }_{\mathrm{cr}}$, where ${\lambda }_{\mathrm{cr}}\equiv \max [-4V(\varphi )/|\varphi {|}^4]$ with the false vacuum being at $\varphi =0$ and $V(0)=0$. We derive this bound on the bounce action \textit{without solving the equation of motion explicitly}. Our bound is derived by a quite simple discussion, and it provides useful information even if it is difficult to obtain the explicit form of the bounce solution. Our bound offers a sufficient condition for the stability of a false vacuum, and it is useful as a quick check on the vacuum stability for given models. Our bound can be applied to a broad class of scalar potential with any number of scalar fields. We also discuss a necessary condition for the bounce action taking a value close to this lower bound.

    hep-phhep-thPRL(2018)·7 citations
23. 23*

    Wigner function and kinetic phenomena for chiral plasma in a strong magnetic field

    E. V. Gorbar🇺🇦 · V. A. Miransky🇨🇦 · I. A. Shovkovy🇺🇸 · P. O. Sukhachov🇨🇦

    By using the exact solutions of the Weyl equation in a constant magnetic field, the equal-time Wigner function for magnetized chiral plasma is derived. It is found that the dependence of the Wigner function on the component of momentum along the magnetic field is asymmetric and is correlated with the fermion chirality. Such a dependence is principal for reproducing the correct chiral magnetic and chiral separation effects. In the lowest Landau level approximation, the equation for the equal-time Wigner function in a strong magnetic field is derived. By making use of this equation, it is found that the longitudinal collective modes in a strong magnetic field are gapped plasmons whose gap is determined by the magnetic field. Unlike the ordinary magnetic field, an axial one allows for the dispersion law of the collective excitations asymmetric in the wave vector. The thermoelectric phenomena for chiral fermions in strong magnetic and axial magnetic fields are studied and the corresponding transport coefficients are calculated.

    hep-phcond-mat.mes-hallhep-thJHEP(2017)·20 citations
24. 24*

    Inclusive spin-momentum analysis and new physics at a polarized electron-positron collider

    B. Ananthanarayan🇮🇳 · Saurabh D. Rindani🇮🇳

    We consider the momentum distribution and the polarization of an inclusive heavy fermion in a process assumed to arise from standard-model (SM) $s$-channel exchange of a virtual $\gamma$ or $Z$ with a further contribution from physics beyond the standard model involving $s$-channel exchanges. The interference of the new physics amplitude with the SM $\gamma$ or $Z$ exchange amplitude is expressed entirely in terms of the space-time signature of such new physics. Transverse as well as longitudinal polarizations of the electron and positron beams are taken into account. Similarly, we consider the cases of the polarization of the observed final-state fermion along longitudinal and two transverse spin-quantization axes which are required for a full reconstruction of the spin dependence of the process. We show how these model-independent distributions can be used to deduce some general properties of the nature of the interaction and some of their properties in prior work which made use of spin-momentum correlations.

    hep-phEPJC(2018)·2 citations
25. 25*

    Holographic QCD in the Veneziano limit at finite Magnetic Field and Chemical Potential

    Umut Gursoy🇳🇱 · Matti Jarvinen🇫🇷 · Govert Nijs🇳🇱

    We investigate the phase diagram of QCD-like gauge theories at strong coupling at finite magnetic field $B$, temperature $T$ and baryon chemical potential $\mu$ using the improved holographic QCD model including the full backreaction of the quarks in the plasma. In addition to the phase diagram we study the behavior of the quark condensate as a function of $T$, $B$ and $\mu$ and discuss the fate of (inverse) magnetic catalysis at finite $\mu$. In particular we observe that inverse magnetic catalysis exists only for small values of the baryon chemical potential. The speed of sound in this holographic quark-gluon plasma exhibits interesting dependence on the thermodynamic parameters.

    ↳ hep-thhep-lathep-phPRL(2018)·73 citations
26. 26*

    Effect of the charged-lepton's mass on the quasielastic neutrino cross sections

    Artur M. Ankowski🇺🇸

    Martini et al. [Phys. Rev. C 94, 015501 (2016)] recently observed that when the produced-lepton's mass plays an important role, the charged-current quasielastic cross section for muon neutrinos can be higher than that for electron neutrinos. Here I argue that this effect appears solely in the theoretical descriptions of nuclear effects in which nucleon knockout requires the energy and momentum transfers to lie in a narrow range of the kinematically allowed values.

    ↳ nucl-thhep-exhep-phPRC(2017)·22 citations
27. 27*

    Symmetries and conservation laws in non-Hermitian field theories

    Jean Alexandre🇬🇧 · Peter Millington🇬🇧 · Dries Seynaeve🇬🇧

    Anti-Hermitian mass terms are considered, in addition to Hermitian ones, for PT-symmetric complex-scalar and fermionic field theories. In both cases, the Lagrangian can be written in a manifestly symmetric form in terms of the PT-conjugate variables, allowing for an unambiguous definition of the equations of motion. After discussing the resulting constraints on the consistency of the variational procedure, we show that the invariance of a non-Hermitian Lagrangian under a continuous symmetry transformation does not imply the existence of a corresponding conserved current. Conserved currents exist, but these are associated with transformations under which the Lagrangian is not invariant and which reflect the well-known interpretation of PT-symmetric theories in terms of systems with gain and loss. A formal understanding of this unusual feature of non-Hermitian theories requires a careful treatment of Noether's theorem, and we give specific examples for illustration.

    ↳ hep-thhep-phPRD(2017)·72 citations
28. 28*

    Top mass from asymptotic safety

    Astrid Eichhorn🇩🇪 · Aaron Held🇩🇪

    We discover that asymptotically safe quantum gravity could predict the top-quark mass. For a broad range of microscopic gravitational couplings, quantum gravity could provide an ultraviolet completion for the Standard Model by triggering asymptotic freedom in the gauge couplings and bottom Yukawa and asymptotic safety in the top-Yukawa and Higgs-quartic coupling. We find that in a part of this range, a difference of the top and bottom mass of approximately $170\mathrm{GeV}$ is generated and the Higgs mass is determined in terms of the top mass. Assuming no new physics below the Planck scale, we construct explicit Renormalization Group trajectories for Standard Model and gravitational couplings which link the transplanckian regime to the electroweak scale and yield a top pole mass of $M_{\text{t,pole}}\approx 171\mathrm{GeV}$.

    ↳ hep-thgr-qchep-phPLB(2018)·170 citations
29. 29*

    Sudden Future Singularities in Quintessence and Scalar-Tensor Quintessence Models

    A. Lymperis🇬🇷 · L. Perivolaropoulos🇬🇷 · S. Lola🇬🇷

    We demonstrate analytically and numerically the existence of geodesically complete singularities in quintessence and scalar tensor quintessence models with scalar field potential of the form $V(\varphi )\sim |\varphi {|}^n$ with $0<n<1$. In the case of quintessence, the singularity which occurs at $\varphi =0$, involves divergence of the third time derivative of the scale factor (Generalized Sudden Future Singularity (GSFS)), and of the second derivative of the scalar field. In the case of scalar-tensor quintessence with the same potential and with a linear minimal coupling ($F(\varphi )=1-\lambda \varphi$), the singularity is stronger and involves divergence of the second derivative of the scale factor (Sudden Future Singularity (SFS)). We show that the scale factor close to the singularity is of the form $a(t)=a_s+b(t_s-t)+c(t_s-t{)}^2+d(t_s-t{)}^q$ where $a_s,b,c,d$ are constants obtained from the dynamical equations and $t_s$ is the time of the singularity. In the case of quintessence we find $q=n+2$ (ie $2<q<3$), while for the case of scalar-tensor quintessence $q=n+1$ ($1<q<2$). We verify these analytical results numerically and extend them to the case where a perfect fluid is present. The linear and quadratic terms in $(t_s-t)$ that appear in the expansion of the scale factor around $t_s$ are subdominant for the diverging derivatives close to the singularity, but can play an important role in the estimation of the Hubble parameter. Using the analytically derived relations between these terms, we derive relations involving the Hubble parameter close to the singularity, which may be used as observational signatures of such singularities in this class of models. For quintessence with matter fluid, we find that close to the singularity $\dot{H}=\frac{3}{2}{\Omega }_{0m}(1+z_s{)}^3-3H^2$.

    ↳ gr-qchep-phhep-thPRD(2017)·8 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.