Wed·Jul 20, 2016Wednesday·July 20, 2016

1. 01*

   Helicity Selection Rules and Non-Interference for BSM Amplitudes

   Aleksandr Azatov🇮🇹 · Roberto Contino🇨🇭 · Camila S. Machado🇧🇷 · Francesco Riva🇨🇭

   Precision studies of scattering processes at colliders provide powerful indirect constraints on new physics. We study the helicity structure of scattering amplitudes in the SM and in the context of an effective Lagrangian description of BSM dynamics. Our analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 to 2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. In such situations, the naive expectation that dimension-6 operators represent the leading BSM contribution is compromised, as corrections from dimension-8 operators can become equally (if not more) important well within the validity of the effective field theory approach.

   hep-phPRD(2017)·182 citations
2. 02*

   Nonlinear dynamics from the relativistic Boltzmann equation in the Friedmann-Lemaître-Robertson-Walker spacetime

   D. Bazow🇺🇸 · G. S. Denicol🇧🇷 · U. Heinz🇺🇸 · M. Martinez🇺🇸 · J. Noronha🇧🇷

   The dissipative dynamics of an expanding massless gas with constant cross section in a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe is studied. The mathematical problem of solving the full nonlinear relativistic Boltzmann equation is recast into an infinite set of nonlinear ordinary differential equations for the moments of the one-particle distribution function. Momentum-space resolution is determined by the number of non-hydrodynamic modes included in the moment hierarchy, i.e., by the truncation order. We show that in the FLRW spacetime the non-hydrodynamic modes decouple completely from the hydrodynamic degrees of freedom. This results in the system flowing as an ideal fluid while at the same time producing entropy. The solutions to the nonlinear Boltzmann equation exhibit transient tails of the distribution function with nontrivial momentum dependence. The evolution of this tail is not correctly captured by the relaxation time approximation nor by the linearized Boltzmann equation. However, the latter probes additional high-momentum details unresolved by the relaxation time approximation. While the expansion of the FLRW spacetime is slow enough for the system to move towards (and not away from) local thermal equilibrium, it is not sufficiently slow for the system to actually ever reach complete local equilibrium. Equilibration is fastest in the relaxation time approximation, followed, in turn, by kinetic evolution with a linearized and a fully nonlinear Boltzmann collision term.

   hep-phcond-mat.stat-mechgr-qchep-th+1PRD(2016)·58 citations
3. 03*

   Lepton flavor violating Z decays: A promising window to low scale seesaw neutrinos

   V. De Romeri🇪🇸 · M.J. Herrero🇪🇸 · X. Marcano🇪🇸 · F. Scarcella🇪🇸

   In this paper we study the Lepton Flavor Violating $Z$ boson decays $Z\to \tau \mu$ and $Z\to \tau e$ in the context of low scale seesaw models with new heavy Majorana neutrinos whose masses could be reachable at the LHC. Our computations of the decay rates are done in the particular realization given by the Inverse Seesaw Model with six extra heavy neutrinos which are quasi-degenerate in three pseudo-Dirac pairs. In particular, we focus on scenarios that are built ad-hoc to produce suppressed rates in all the processes involving $\mu$-$e$ transitions, given the fact that these are by far the most strongly constrained by present data. We will fully explore the $Z\to \tau \mu$ and $Z\to \tau e$ rates, together with a set of observables that we find to be the most constraining ones, and we will conclude that sizable rates of up to $2\times 10^{-7}$, accessible at future colliders, can be reached in this model for Majorana masses in the few TeV range, potentially reachable at LHC.

   hep-phPRD(2017)·67 citations
4. 04*

   Littlest Seesaw model from S4 x U(1)

   Stephen F. King🇬🇧 · Christoph Luhn🇩🇪

   We show how a minimal (littlest) seesaw model involving two right-handed neutrinos and a very constrained Dirac mass matrix, with one texture zero and two independent Dirac masses, may arise from $S_4\times U(1)$ symmetry in a semi-direct supersymmetric model. The resulting CSD3 form of neutrino mass matrix only depends on two real mass parameters plus one undetermined phase. We show how the phase may be fixed to be one of the cube roots of unity by extending the $S_4\times U(1)$ symmetry to include a product of $Z_3$ factors together with a CP symmetry, which is spontaneously broken leaving a single residual $Z_3$ in the charged lepton sector and a residual $Z_2$ in the neutrino sector, with suppressed higher order corrections. With the phase chosen from the cube roots of unity to be $-2\pi /3$, the model predicts a normal neutrino mass hierarchy with $m_1=0$, reactor angle ${\theta }_{13}=8.7^{\circ }$, solar angle ${\theta }_{12}=34^{\circ }$, atmospheric angle ${\theta }_{23}=44^{\circ }$, and CP violating oscillation phase ${\delta }_{\mathrm{CP}}=-93^{\circ }$, depending on the fit of the model to the neutrino masses.

   hep-phJHEP(2016)·59 citations
5. 05*

   A Consistent Theory of Decaying Dark Matter Connecting IceCube to the Sesame Street

   Marco Chianese🇮🇹 · Alexander Merle🇩🇪

   The high energy events observed at the IceCube Neutrino Observatory have triggered many investigations interpreting the highly energetic neutrinos detected as decay products of heavy unstable Dark Matter particles. However, while very detailed treatments of the IceCube phenomenology exist, only a few references focus on the (non-trivial) Dark Matter production part -- and all of those rely on relatively complicated new models which are not always testable directly. We instead investigate two of the most minimal scenarios possible, where the operator responsible for the IceCube events is directly involved in Dark Matter production. We show that the simplest (four-dimensional) operator is not powerful enough to accommodate all constraints. A more non-minimal setting (at mass dimension six), however, can do both fitting all the data and also allowing for a comparatively small parameter space only, parts of which can be in reach of future observations. We conclude that minimalistic approaches can be enough to explain all data required, while complicated new physics seems not to be required by IceCube.

   hep-phastro-ph.COastro-ph.HEJCAP(2017)·51 citations
6. 06*

   Accurate predictions for charged Higgs production: closing the $m_{H^{\pm }}\sim m_t$ window

   Celine Degrande🇬🇧 · Rikkert Frederix🇩🇪 · Valentin Hirschi🇺🇸 · Maria Ubiali🇬🇧 · Marius Wiesemann🇨🇭 · Marco Zaro🇫🇷

   We present predictions for the total cross section for the production of a charged Higgs boson in the intermediate-mass range ($m_{H^{\pm }}\sim m_t$) at the LHC, focusing on a type-II two-Higgs-doublet model. Results are obtained at next-to-leading order (NLO) accuracy in QCD perturbation theory, by studying the full process $pp\to H^{\pm }{W}^{\mp }b\bar{b}$ in the complex-(top)-mass scheme with massive bottom quarks. Compared to lowest-order predictions, NLO corrections have a sizeable impact: they increase the cross section by roughly 50\% and reduce uncertainties due to scale variations by more than a factor of two. Our computation reliably interpolates between the low- and high-mass regime. Our results provide the first NLO prediction for charged Higgs production in the intermediate-mass range and therefore allow to have NLO accurate predictions in the full $m_{H^{\pm }}$ range. The extension of our results to different realisations of the two-Higgs-doublet model or to the supersymmetric case is also discussed.

   hep-phhep-exPLB(2017)·78 citations
7. 07*

   Associated production of a top pair and a W boson at next-to-next-to-leading logarithmic accuracy

   Alessandro Broggio🇩🇪 · Andrea Ferroglia🇺🇸 · Giovanni Ossola🇺🇸 · Ben D. Pecjak🇬🇧

   We consider soft gluon emission corrections to the production of a top-antitop pair in association with a W boson at the Large Hadron Collider. We obtain a soft-gluon resummation formula for this production process which is valid up to next-to-next-to-leading logarithmic accuracy. We evaluate the soft gluon resummation formula in Mellin space by means of an in-house parton level Monte Carlo code which allows us to obtain predictions for the total cross section as well as for several differential distributions. We study the impact of the soft-gluon resummation corrections in comparison to fixed order calculations.

   hep-phJHEP(2016)·63 citations
8. 08*

   Higgs production in association with a top-antitop pair in the Standard Model Effective Field Theory at NLO in QCD

   Fabio Maltoni🇧🇪 · Eleni Vryonidou🇧🇪 · Cen Zhang🇺🇸

   We present the results of the computation of the next-to-leading order QCD corrections to the production cross section of a Higgs boson in association with a top-antitop pair at the LHC, including the three relevant dimension-six operators ($O_{t\phi },O_{\phi G},O_{tG}$) of the standard model effective field theory. These operators also contribute to the production of Higgs bosons in loop-induced processes at the LHC, such as inclusive Higgs, $Hj$ and $HH$ production, and modify the Higgs decay branching ratios for which we also provide predictions. We perform a detailed study of the cross sections and their uncertainties at the total as well as differential level and of the structure of the effective field theory at NLO including renormalisation group effects. Finally, we show how the combination of information coming from measurements of these production processes will allow to constrain the three operators at the current and future LHC runs. Our results lead to a significant improvement of the accuracy and precision of the deviations expected from higher-dimensional operators in the SM in both the top-quark and the Higgs-boson sectors and provide a necessary ingredient for performing a global EFT fit to the LHC data at NLO accuracy.

   hep-phhep-exJHEP(2016)·153 citations
9. 09*

   Towards gauge unified, supersymmetric hidden strong dynamics

   Cheng-Wei Chiang🇹🇼 · Sichun Sun🇹🇼 · Fang Ye🇹🇼

   We consider a class of models with extra complex scalars that are charged under both the Standard Model and a hidden strongly coupled $SU(N{)}_H$ gauge sector, and discuss the scenarios where the new scalars are identified as the messenger fields that mediate the spontaneously broken supersymmetries from the hidden sector to the visible sector. The new scalars are embedded into 5-plets and 10-plets of an $SU(5{)}_V$ gauge group that potentially unifies the Standard Model gauge groups. The Higgs bosons remain as elementary particles. In the supersymmetrized version of this class of models, vector-like fermions whose left-handed components are superperpartners of the new scalars are introduced. Due to the hidden strong force, the new low-energy scalars hadronize before decaying and thus evade the common direct searches of the supersymmetric squarks. This can be seen as a gauge mediation scenario with the scalar messenger fields forming low-energy bound states. We also discuss the possibility that among the tower of bound states formed under hidden strong dynamics (at least the TeV scale) one of them is the dark matter candidate, as well as the collider signatures (e.g. diphoton, diboson or dijet) of the models that may show up in the near future.

   hep-phhep-thCPC(2021)·3 citations
10. 10*

    Flavor physics induced by light $Z^{\prime }$ from SO(10) GUT

    Junji Hisano🇯🇵 · Yu Muramatsu🇰🇷 · Yuji Omura🇯🇵 · Yoshihiro Shigekami🇯🇵

    In this paper, we investigate predictions of the SO(10) Grand Unified Theory (GUT), where an extra U(1)${}^{\prime }$ gauge symmetry remains up to the supersymmetry (SUSY) breaking scale. The minimal setup of SO(10) GUT unifies quarks and leptons into a $16$-representational field in each generations. The setup, however, suffers from the realization of the realistic Yukawa couplings at the electroweak scale. In order to solve this problem, we introduce $10$-representational matter fields, and then the two kinds of matter fields mix with each other at the SUSY breaking scale, where the extra U(1)${}^{\prime }$ gauge symmetry breaks down radiatively. One crucial prediction is that the Standard Model quarks and leptons are given by the linear combinations of the fields with two different U(1)${}^{\prime }$ charges. The mixing also depends on the flavor. Consequently, the U(1)${}^{\prime }$ interaction becomes flavor violating, and the flavor physics is the smoking-gun signal of our GUT model. The flavor violating $Z^{\prime }$ couplings are related to the fermion masses and the CKM matrix, so that we can derive some explicit predictions in flavor physics. We especially discuss $K$-$\overline{K}$ mixing, $B_{(s)}$-$\overline{B_{(s)}}$ mixing, and the (semi)leptonic decays of $K$ and $B$ in our model. We also study the flavor violating $\mu$ and $\tau$ decays and discuss the correlations among the physical observables in this SO(10) GUT framework.

    hep-phhep-exJHEP(2016)·9 citations
11. 11*

    On enhanced corrections from quasi-degenerate states to heavy quarkonium observables

    Yuichiro Kiyo🇯🇵 · Go Mishima🇯🇵 · Yukinari Sumino🇯🇵

    It is well known that in perturbation theory existence of quasi-degenerate states can rearrange the order counting. For a heavy quarkonium system, naively, enhanced effects ($l$-changing mixing effects) could contribute already to the first-order and third-order corrections to the wave function and the energy level, respectively, in expansion in ${\alpha }_s$. We present a formulation and note that the corresponding (lowest-order) corrections vanish due to absence of the relevant off-diagonal matrix elements. As a result, in the quarkonium energy level and leptonic decay width, the enhanced effects are expected to appear, respectively, in the fifth- and fourth-order corrections and beyond.

    hep-phPLB(2016)·1 citation
12. 12*

    Simplified Limits on Resonances at the LHC

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

    In the earliest stages of evaluating new collider data, especially if a small excess may be present, it would be useful to have a method for comparing the data with entire classes of models, to get an immediate sense of which classes could conceivably be relevant. In this paper, we propose a method that applies when the new physics invoked to explain the excess corresponds to the production and decay of a single, relatively narrow, $s$-channel resonance. A simplifed model of the resonance allows us to convert an estimated signal cross section into model-independent bounds on the product of the branching ratios corresponding to production and decay. This quickly reveals whether a given class of models could possibly produce a signal of the required size at the LHC. Our work sets up a general framework, outlines how it operates for resonances with different numbers of production and decay modes, and analyzes cases of current experimental interest, including resonances decaying to dibosons, diphotons, dileptons, or dijets. If the LHC experiments were to report their searches for new resonances beyond the standard model in the simplified limits variable $\zeta$ defined in this paper, that would make it far easier to avoid blind alleys and home in on the most likely candidate models to explain any observed excesses.

    hep-phhep-exPRD(2016)·8 citations
13. 13*

    Doubling Up on Supersymmetry in the Higgs Sector

    John Ellis🇬🇧 · Jérémie Quevillon🇬🇧 · Verónica Sanz🇬🇧

    We explore the possibility that physics at the TeV scale possesses approximate $N=2$ supersymmetry, which is reduced to the $N=1$ minimal supersymmetric extension of the Standard Model (MSSM) at the electroweak scale. This doubling of supersymmetry modifies the Higgs sector of the theory, with consequences for the masses, mixings and couplings of the MSSM Higgs bosons, whose phenomenological consequences we explore in this paper. The mass of the lightest neutral Higgs boson $h$ is independent of $\tan \beta$ at the tree level, and the decoupling limit is realized whatever the values of the heavy Higgs boson masses. Radiative corrections to the top quark and stop squarks dominate over those due to particles in $N=2$ gauge multiplets. We assume that these radiative corrections fix $m_h\simeq 125$ GeV, whatever the masses of the other neutral Higgs bosons $H,A$, a scenario that we term the $h$2MSSM. Since the $H,A$ bosons decouple from the $W$ and $Z$ bosons in the $h$2MSSM at tree level, only the LHC constraints on $H,A$ and $H^{\pm }$ couplings to fermions are applicable. These and the indirect constraints from LHC measurements of $h$ couplings are consistent with $m_A\gtrsim 200$ GeV for $\tan \beta \in (2,8)$ in the $h$2MSSM.

    hep-phhep-exJHEP(2016)·24 citations
14. 14*

    Effective Multi-Higgs Couplings to Gluons

    Michael Spira🇨🇭

    Standard-Model Higgs bosons are dominantly produced via the gluon-fusion mechanism $gg\to H$ at the LHC, i.e. in a loop-mediated process with top loops providing the dominant contribution. For the measured Higgs boson mass of $\sim 125$ GeV the limit of heavy top quarks provides a reliable approximation as long as the relative QCD corrections are scaled with the full mass-dependent LO cross section. In this limit the Higgs coupling to gluons can be described by an effective Lagrangian. The same approach can also be applied to the coupling of more than one Higgs boson to gluons. We will derive the effective Lagrangian for multi-Higgs couplings to gluons up to N${}^4$LO thus extending previous results for more than one Higgs boson. Moreover we discuss gluonic Higgs couplings up to NNLO, if several heavy quarks contribute.

    hep-phJHEP(2016)·50 citations
15. 15*

    Non-zero ${\theta }_{13}$ with Unbroken $\mu -\tau$ Symmetry of the Active Neutrino Mass Matrix in the Presence of a Light Sterile Neutrino

    Debasish Borah🇮🇳

    We revisit the possibility of generating non-zero reactor mixing angle in a scenario where there is a sterile neutrino at the eV scale apart from the usual three sub-eV scale active neutrinos. We show that the $3\times 3$ active neutrino mass matrix can possess a $\mu -\tau$ symmetry and can still be consistent with non-zero value of the reactor mixing angle ${\theta }_{13}$, if this $\mu -\tau$ symmetry is broken in the sterile neutrino sector. We first propose a simple model based on the discrete flavour symmetry $A_4\times Z_3\times Z_3^{\prime }$ to realise such a scenario and then numerically evaluate the complete $3+1$ neutrino parameter space that allows such a possibility. We show that, such a possibility of generating non-zero ${\theta }_{13}$ can in general, remain valid even if the present $3+1$ neutrino global fit data get ruled out by future experiments. We also discuss the possible implications at neutrinoless double beta decay $(0\nu \beta \beta )$ experiments in view of the latest results from KamLAND-Zen experiment.

    hep-phPRD(2017)·14 citations
16. 16*

    Is the newly reported $X(5568)$ a $B\bar{K}$ molecular state?

    Rui Chen🇨🇳 · Xiang Liu🇨🇳

    In this work, we perform a dynamical study of the $B^{(\ast )}$ and $\bar{K}$ interaction and show that the newly reported $X(5568)$ or $X(5616)$ cannot be assigned to be an isovector $B\bar{K}$ or $B^{\ast }\bar{K}$ molecular state. We continue to investigate the isoscalar $B^{(\ast )}\bar{K}$ systems, and the $B^{(\ast )}\bar{K}$ systems with isospin $I=0,1$, and predict the existence of several isoscalar $B^{(\ast )}{\bar{K}}^{(\ast )}$ molecular states. A new task of exploring open-bottom molecular states will be created for future experiments.

    hep-phPRD(2016)·34 citations
17. 17*

    Charmed Mesons and Charmonia: Three-Meson Strong Couplings

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇷🇺 · Hagop Sazdjian🇫🇷 · Silvano Simula🇮🇹

    Revisiting the strong couplings of three mesons, each of which involves at least one charm quark, proves clear disaccord between quark-model and QCD sum-rule results.

    hep-phnucl-thEPJ Web Conf.(2016)·1 citation
18. 18*

    The $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$ in the relativized quark model

    Qi-Fang Lü🇨🇳 · Yu-Bing Dong🇨🇳

    We investigate the masses of $cs\bar{c}\bar{s}$ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential firstly, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schrödinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of $X(4140)$ can be regarded as the $cs\bar{c}\bar{s}$ tetraquark ground states, and the $X(4700)$ can be assigned as the $2S$ excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of $X(4500)$ can be explained as the tetraquark composed of one $2S$ scalar diquark and one scalar antidiquark. In our approach, the $X(4274)$ cannot be explained as a tetraquark state, however, it can be a good candidate of the conventional ${\chi }_{c1}(3^3{P}_1)$ state. In addition, other charmonium-like states ${\chi }_{c0}(3915)$, $X(4350)$, $X(4630)$ and $X(4660)$, as the $cs\bar{c}\bar{s}$ tetraquark states, are also discussed.

    hep-phhep-exnucl-thPRD(2016)·78 citations
19. 19*

    NLO electroweak corrections to off-shell top-antitop production with leptonic decays at the LHC

    Ansgar Denner🇩🇪 · Mathieu Pellen🇩🇪

    For the first time the next-to-leading-order electroweak corrections to the full off-shell production of two top quarks that decay leptonically are presented. This calculation includes all off-shell, non-resonant, and interference effects for the 6-particle phase space. While the electroweak corrections are below one per cent for the integrated cross section, they reach up to 15% in the high-transverse-momentum region of distributions. To support the results of the complete one-loop calculation, we have in addition evaluated the electroweak corrections in two different pole approximations, one requiring two on-shell top quarks and one featuring two on-shell W bosons. While the former deviates by up to 10% from the full calculation for certain distributions, the latter provides a very good description for most observables. The increased centre-of-mass energy of the LHC makes the inclusion of electroweak corrections extremely relevant as they are particularly large in the Sudakov regime where new physics is expected to be probed.

    hep-phJHEP(2016)·97 citations
20. 20*

    Can the $750GeV$ enhancement be a signal of light magnetic monopoles?

    L.N. Epele · H. Fanchiotti · C.A · García Canal · V.A. Mitsou · V. Vento

    The announced ~ 3 {\sigma} enhancement in the inclusive {\gamma} {\gamma} -spectrum at ~ 750 GeV made by the ATLAS and CMS collaborations at LHC might indicate the existence of a monopole-antimonopole bound state: monopolium. In here we revisit our calculation of 2012 from a more general perspective and see that this resonance, if confirmed, might be a first signal of the existence of magnetic monopoles.

    hep-ph17 citations
21. 21*

    Flavon-induced connections between lepton flavour mixing and charged lepton flavour violation processes

    Silvia Pascoli🇬🇧 · Ye-Ling Zhou🇬🇧

    In leptonic flavour models with discrete flavour symmetries, couplings between flavons and leptons can result in special flavour structures after they gain vacuum expectation values. At the same time, they can also contribute to the other lepton-flavour-violating processes. We study the flavon-induced LFV 3-body charged lepton decays and radiative decays and we take as example the $A_4$ discrete symmetry. In $A_4$ models, a $Z_3$ residual symmetry roughly holds in the charged lepton sector for the realisation of tri-bimaximal mixing at leading order. The only processes allowed by this symmetry are ${\tau }^{-}\to {\mu }^{+}{e}^{-}{e}^{-},e^{+}{\mu }^{-}{\mu }^{-}$, and the other 3-body and all radiative decays are suppressed by small $Z_3$-breaking effects. These processes also depend on the representation the flavon is in, whether pseudo-real (case i) or complex (case ii). We calculate the decay rates for all processes for each case and derive their strong connection with lepton flavour mixing. In case i, sum rules for the branching ratios of these processes are obtained, with typical examples $\text{Br}({\tau }^{-}\to {\mu }^{+}{e}^{-}{e}^{-})\approx \text{Br}({\tau }^{-}\to e^{+}{\mu }^{-}{\mu }^{-})$ and $\text{Br}({\tau }^{-}\to e^{-}\gamma )\approx \text{Br}({\tau }^{-}\to {\mu }^{-}\gamma )$. In case ii, we observe that the mixing between two $Z_3$-covariant flavons plays an important role. All processes are suppressed by charged lepton masses and current experimental constraints allow the electroweak scale and the flavon masses to be around hundreds of GeV. Our discussion can be generalised in other flavour models with different flavour symmetries.

    hep-phJHEP(2016)·24 citations
22. 22*

    Pictures of Particle Production in Proton-Nucleus Collisions

    Alfred H. Mueller🇺🇸

    This work focuses on gluon(jet) production in dilute(proton)-dense(nucleus) collisions. Depending on the frame and gauge, gluon production can be viewed as a freeing of gluons coming from either the proton wave function or from the nucleus wave function. These (apparently) very different pictures must lead to the same result and the purpose of this paper is to see how that happens. The focus is on gluons having $k_{\perp }\sim Q_S$ or gluons in the scaling region $k_{\perp }/Q_S\gg 1$. In the McLerran-Venugopalan(MV) model with $k_{\perp }\sim Q_S$ we are able to derive gluon production in a way that (graphically) manifestly shows $k_{\perp }$-factorization in terms of the number density of gluons in the nuclear wave function. We presume that this picture, and $k_{\perp }$-factorization, continues to hold in the presence of small-$x$ evolution although we have not been able to explicitly verify this. Our result is in agreement with usual $k_{\perp }$-factorization where the gluon number density of the nucleus does not appear in an explicit way.

    hep-phActa Phys.Polon.B(2016)·4 citations
23. 23*

    Quasi-Dirac neutrinos at the LHC

    G. Anamiati🇪🇸 · M. Hirsch🇪🇸 · E. Nardi🇮🇹

    Lepton number violation is searched for at the LHC using same-sign leptons plus jets. The standard lore is that the ratio of same-sign lepton to opposite-sign lepton events, $R_{ll}$, is equal to $R_{ll}=1$ ($R_{ll}=0$) for Majorana (Dirac) neutrinos. We argue that for "quasi-Dirac" neutrinos, $R_{ll}$ can have any value between 0 and 1, the precise value being controlled by the mass splitting versus the width of the quasi-Dirac resonances. A measurement of $R_{ll}\ne 0,1$ would then contain valuable information about the origin of neutrino masses. We consider as an example the inverse seesaw mechanism in a left-right symmetric scenario, which is phenomenologically particularly interesting since all the heavy states in the high energy completion of the model could be within experimental reach. A prediction of this scenario is a correlation between the values of $R_{ll}$ and the ratio between the rates for heavy neutrino decays into standard model gauge bosons, and into three body final states $ljj$ mediated by off-shell $W_R$ exchange.

    hep-phJHEP(2016)·122 citations
24. 24*

    Yukawa CFTs and Emergent Supersymmetry

    Lin Fei🇺🇸 · Simone Giombi🇺🇸 · Igor R. Klebanov🇺🇸 · Grigory Tarnopolsky🇺🇸

    We study conformal field theories with Yukawa interactions in dimensions between 2 and 4; they provide UV completions of the Nambu-Jona-Lasinio and Gross-Neveu models which have four-fermion interactions. We compute the sphere free energy and certain operator scaling dimensions using dimensional continuation. In the Gross-Neveu CFT with $N$ fermion degrees of freedom we obtain the first few terms in the $4-ϵ$ expansion using the Gross-Neveu-Yukawa model, and the first few terms in the $2+ϵ$ expansion using the four-fermion interaction. We then apply Pade approximants to produce estimates in $d=3$. For $N=1$, which corresponds to one 2-component Majorana fermion, it has been suggested that the Yukawa theory flows to a $\mathcal{N}=1$ supersymmetric CFT. We provide new evidence that the $4-ϵ$ expansion of the $N=1$ Gross-Neveu-Yukawa model respects the supersymmetry. Our extrapolations to $d=3$ appear to be in good agreement with the available results obtained using the numerical conformal bootstrap. Continuation of this CFT to $d=2$ provides evidence that the Yukawa theory flows to the tri-critical Ising model. We apply a similar approach to calculate the sphere free energy and operator scaling dimensions in the Nambu-Jona-Lasinio-Yukawa model, which has an additional $U(1)$ global symmetry. For $N=2$, which corresponds to one 2-component Dirac fermion, this theory has an emergent supersymmetry with 4 supercharges, and we provide new evidence for this.

    ↳ hep-thcond-mat.str-elhep-phPTEP(2016)·139 citations
25. 25*

    SUSY breaking after inflation in supergravity with inflaton in a massive vector multiplet

    Yermek Aldabergenov🇯🇵 · Sergei V. Ketov🇯🇵

    We propose a limited class of models, describing interacting chiral multiplets with a non-minimal coupling to a vector multiplet, in curved superspace of $N=1$ supergravity. Those models are suitable for the inflationary model building in supergravity with inflaton assigned to a massive vector multiplet and spontaneous SUSY breaking in Minkowski vacuum after inflation, for any values of the inflationary parameters $n_s$ and $r$, and any scale of SUSY breaking.

    ↳ hep-thgr-qchep-phPLB(2016)·30 citations
26. 26*

    Randall-Sundrum brane-world in modified gravity

    Hiroshi Nakada🇯🇵 · Sergei V. Ketov🇯🇵

    We modify Randall-Sundrum model of brane-world (with two branes) by adding the scalar curvature squared term in five dimensions. We find that it does not destabilize Randall-Sundrum solution to the hierarchy problem of the Standard Model in particle physics.

    ↳ hep-thgr-qchep-phPRD(2016)·8 citations
27. 27*

    Revisit of the interacting holographic dark energy model after Planck 2015

    Lu Feng🇨🇳 · Xin Zhang🇨🇳

    We investigate the observational constraints on the interacting holographic dark energy model. We consider five typical interacting models with the interaction terms $Q=3\beta H{\rho }_{\mathrm{de}}$, $Q=3\beta H{\rho }_{\mathrm{c}}$, $Q=3\beta H({\rho }_{\mathrm{de}}+{\rho }_{\mathrm{c}})$, $Q=3\beta H\sqrt{{\rho }_{\mathrm{de}}{\rho }_{\mathrm{c}}}$, and $Q=3\beta H\frac{{\rho }_{\mathrm{de}}{\rho }_c}{{\rho }_{\mathrm{de}}+{\rho }_{\mathrm{c}}}$, respectively, where $\beta$ is a dimensionless coupling constant. The observational data we use in this paper include the JLA compilation of type Ia supernovae data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the Hubble constant direct measurement. We make a comparison for these five interacting holographic dark energy models by employing the information criteria, and we find that, within the framework of holographic dark energy, the $Q=3\beta H\frac{{\rho }_{\mathrm{de}}{\rho }_{\mathrm{c}}}{{\rho }_{\mathrm{de}}+{\rho }_{\mathrm{c}}}$ model is most favored by current data, and the $Q=3\beta H{\rho }_{\mathrm{c}}$ model is relatively not favored by current data. For the $Q=3\beta H{\rho }_{\mathrm{de}}$ and $Q=3\beta H\frac{{\rho }_{\mathrm{de}}{\rho }_{\mathrm{c}}}{{\rho }_{\mathrm{de}}+{\rho }_{\mathrm{c}}}$ models, a positive coupling $\beta$ can be detected at more than 2$\sigma$ significance.

    ↳ astro-ph.COgr-qchep-phJCAP(2016)·77 citations
28. 28*

    Detecting supernova neutrinos with iron and lead detectors

    Abhijit Bandyopadhyay (RKMVU)🇮🇳 · Pijushpani Bhattacharjee (SINP)🇮🇳 · Sovan Chakraborty (IIT-Guwahati)🇩🇪 · Kamales Kar (RKMVU)🇮🇳 · Satyajit Saha (SINP)🇮🇳

    Supernova (SN) neutrinos can excite the nuclei of various detector materials beyond their neutron emission thresholds through charged current (CC) and neutral current (NC) interactions. The emitted neutrons, if detected, can be a signal for the supernova event. Here we present the results of our study of SN neutrino detection through the neutron channel in lead (${}^{208}\mathrm{Pb}$) and iron (${}^{56}\mathrm{Fe}$) detectors for realistic neutrino fluxes and energies given by the recent Basel/Darmstadt simulations for a 18 solar mass progenitor SN at a distance of 10 kpc. We find that, in general, the number of neutrons emitted per kTon of detector material for the neutrino luminosities and average energies of the different neutrino species as given by the Basel/Darmstadt simulations are significantly lower than those estimated in previous studies based on the results of earlier SN simulations. At the same time, we highlight the fact that, although the total number of neutrons produced per kTon in a iron detector is more than an order of magnitude lower than that for lead, the dominance of the flavor blind NC events in the case of iron, as opposed to dominance of ${\nu }_e$ induced CC events in the case of lead, offers a complementarity between the two detector materials so that simultaneous detection of SN neutrinos in a lead and a sufficiently large iron detector suitably instrumented for neutron detection may allow estimating the fraction of the total $\mu$ and $\tau$ flavored neutrinos in the SN neutrino flux and thereby probing the emission mechanism as well as flavor oscillation scenarios of the SN neutrinos.

    ↳ astro-ph.HEhep-phnucl-exPRD(2017)·14 citations
29. 29*

    Redshift drift constraints on holographic dark energy

    Dong-Ze He🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    The Sandage-Loeb (SL) test is a promising method for probing dark energy because it measures the redshift drift in the spectra of Lyman-$\alpha$ forest of distant quasars, covering the "redshift desert" of $2\lesssim z\lesssim 5$, which is not covered by existing cosmological observations. Therefore, it could provide an important supplement to current cosmological observations. In this paper, we explore the impact of SL test on the precision of cosmological constraints for two typical holographic dark energy models, i.e., the original holographic dark energy (HDE) model and the Ricci holographic dark energy (RDE) model. To avoid data inconsistency, we use the best-fit models based on current combined observational data as the fiducial models to simulate 30 mock SL test data. The results show that SL test can effectively break the existing strong degeneracy between the present-day matter density ${\Omega }_{m0}$ and the Hubble constant $H_0$ in other cosmological observations. For the considered two typical dark energy models, not only can a 30-year observation of SL test improve the constraint precision of ${\Omega }_{m0}$ and $h$ dramatically, but can also enhance the constraint precision of the model parameters $c$ and $\alpha$ significantly.

    ↳ astro-ph.COhep-phSCPMA(2017)·20 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.