Wed·Dec 23, 2015Wednesday·December 23, 2015

1. 01*

   750 GeV Diphotons from a D3-brane

   Jonathan J. Heckman🇺🇸

   Motivated by the recently reported diphoton excess at 750 GeV observed by both CMS and ATLAS, we study string-based particle physics models which can accommodate this signal. Quite remarkably, although Grand Unified Theories in F-theory tend to impose tight restrictions on candidate extra sectors, the case of a probe D3-brane near an E-type Yukawa point naturally leads to a class of strongly coupled models capable of accommodating the observed signature. In these models, the visible sector is realized by intersecting 7-branes, and the 750 GeV resonance is a scalar modulus associated with motion of the D3-brane in the direction transverse to the Standard Model 7-branes. Integrating out heavy 3-7 string messenger states leads to dimension five operators for gluon fusion production and diphoton decays. Due to the unified structure of interactions, these models also predict that there should be additional decay channels to ZZ and Z gamma. We also comment on models with distorted unification, where both the production mechanism and decay channels can differ.

   hep-phhep-thNPB(2016)·123 citations
2. 02*

   Perturbativity, vacuum stability and inflation in the light of 750 GeV diphoton excess

   Mansi Dhuria🇮🇳 · Gaurav Goswami🇮🇳

   The recent observation of the 750 GeV diphoton excess at 13 TeV LHC has motivated many scenarios of physics beyond the Standard Model. In this work, we begin by showing that many models which explain the observed excess tend to get strongly coupled well below the Planck scale. We then study a simple scenario involving colored vector-like fermions with exotic charges, which is expected to stay weakly coupled till the Planck scale. We find the conditions under which this happens, derive the Renormalization Group equations for such models and solve them to show that perturbativity till Planck scale can be maintained for a very reasonable choice of parameters. Finally, we discuss issues related to vacuum stability and the possibility of inflation in the scenarios we study.

   hep-phastro-ph.COPRD(2016)·115 citations
3. 03*

   The 750 GeV diphoton excess at the LHC and dark matter constraints

   Xiao-Jun Bi🇨🇳 · Qian-Fei Xiang🇨🇳 · Peng-Fei Yin🇨🇳 · Zhao-Huan Yu🇦🇺

   The recent reported 750 GeV diphoton excess at the 13 TeV LHC is explained in the framework of effective field theory assuming the diphoton resonance is a scalar (pseudoscalar) particle. It is found that the large production rate and the broad width of this resonance are hard to simultaneously explain if only visible final states are considered. Therefore an invisible decay channel to dark matter (DM) is strongly favored by the diphoton excess with a broad width, given a large coupling of the new scalar to DM. We set constraints on the parameter space in this scenario using the results from LHC Run 1, DM relic density, and DM direct and indirect detection experiments. We find that the DM searches can exclude a large portion of the parameter regions accounting for the diphoton excess with a broad width.

   hep-phNPB(2016)·130 citations
4. 04*

   Suppressing gravitino thermal production with a temperature-dependent messenger coupling

   Marcin Badziak🇵🇱 · Ioannis Dalianis🇬🇷 · Zygmunt Lalak🇵🇱

   We show that the constraints on GMSB theories from the gravitino cosmology can be significantly relaxed if the messenger-spurion coupling is temperature dependent. We demonstrate this novel mechanism in a scenario in which this coupling depends on the VEV of an extra singlet field $S$ that interacts with the thermalized plasma which can result in a significantly suppressed gravitino production rate. In such a scenario the relic gravitino abundance is determined by the thermal dynamics of the $S$ field and it is easy to fit the observed dark matter abundance evading the stringent constraints on the reheating temperature, thus making gravitino dark matter consistent with thermal leptogenesis.

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

   Model-independent combination of diphoton constraints at 750 GeV

   Jong Soo Kim🇪🇸 · Krzysztof Rolbiecki🇪🇸 · Roberto Ruiz de Austri🇪🇸

   Motivated by the recent diphoton excess reported by both the ATLAS and CMS collaborations, we provide a model-independent combination of diphoton results obtained at $\sqrt{s}=8$ and 13 TeV at the LHC. We consider resonant s-channel production of a spin-0 and spin-2 particle with a mass of 750 GeV that subsequently decays to two photons. The size of the excess reported by ATLAS appears to be in slight tension with other measurements under the spin-2 particle hypothesis.

   hep-phEPJC(2016)·105 citations
6. 06*

   Effective interpretations of a diphoton excess

   Laure Berthier🇩🇰 · James M. Cline🇨🇦 · William Shepherd🇩🇰 · Michael Trott🇩🇰

   We discuss some consistency tests that must be passed for a successful explanation of a diphoton excess at larger mass scales, generated by a scalar or pseudoscalar state, possibly of a composite nature, decaying to two photons. Scalar states at mass scales above the electroweak scale decaying significantly into photon final states generically lead to modifications of Standard Model Higgs phenomenology. We characterise this effect using the formalism of Effective Field Theory (EFT) and study the modification of the effective couplings to photons and gluons of the Higgs. The modification of Higgs phenomenology comes about in a variety of ways. For scalar $0^{+}$states, the Higgs and the heavy boson can mix. Lower energy phenomenology gives a limit on the mixing angle, which gets generated at one loop in any such theory explaining the diphoton excess. Even if the mixing angle is set to zero, we demonstrate that a relation exists between lower energy Higgs data and a massive scaler decaying to diphoton final states. If the new boson is a pseudoscalar, we note that if it is composite, it is generic to have an excited scalar partner that can mix with the Higgs, which has a stronger coupling to photons. In the case of a pseudoscalar, we also characterize how lower energy Higgs phenomenology is directly modified using EFT, even without assuming a scalar partner of the pseudoscalar state. We find that naturalness concerns can be accommodated, and that pseudoscalar models are more protected from lower energy constraints.

   hep-phJHEP(2016)·110 citations
7. 07*

   Implications of SUSY Searches for Physics Beyond the Standard Model

   Nathaniel Craig🇺🇸

   I discuss some essential features of the electroweak hierarchy problem and the ensuing motivation for weak-scale supersymmetry. Taking the hierarchy problem seriously, null results in searches for SUSY at the LHC favor specific regions of SUSY parameter space. More broadly, they suggest investigating a variety of alternative approaches to the hierarchy problem with diverse experimental signatures.

   hep-ph2 citations
8. 08*

   Exploring the Hadronic Axion Window via Delayed Neutralino Decay to Axinos at the LHC

   C.S. Redino🇺🇸 · D. Wackeroth🇺🇸

   The addition of the QCD axion to the Minimal Supersymmetric Standard Model (MSSM) not only solves the strong CP problem but also modifies the dark sector with new dark matter candidates. While SUSY axion phenomenology is usually restricted to searches for the axion itself or searches for the ordinary SUSY particles, this work focuses on scenarios where the axion's superpartner, the axino, may be detectable at the Large Hadron Collider (LHC) in the decays of neutralinos displaced from the primary vertex. In particular, we focus on the KSVZ axino within the hadronic axion window. The decay length of neutralinos in this scenario easily fits the ATLAS detector for SUSY spectra expected to be testable at the 14 TeV LHC. We compare this signature of displaced decays to axinos to other well motivated scenarios containing a long lived neutralino which decays inside the detector. These alternative scenarios can in some cases very closely mimic the expected axino signature, and the degree to which they are distinguishable is discussed. We also briefly comment on the cosmological viability of such a scenario.

   hep-phPRD(2016)·4 citations
9. 09*

   The 750 GeV Diphoton Excess May Not Imply a 750 GeV Resonance

   Won Sang Cho🇰🇷 · Doojin Kim🇺🇸 · Kyoungchul Kong🇺🇸 · Sung Hak Lim🇰🇷 · Konstantin T. Matchev🇺🇸 · Jong-Chul Park🇰🇷 · Myeonghun Park🇰🇷

   We discuss non-standard interpretations of the 750 GeV diphoton excess recently reported by the ATLAS and CMS Collaborations which do not involve a new, relatively broad, resonance with a mass near 750 GeV. Instead, we consider the sequential cascade decay of a much heavier, possibly quite narrow, resonance into two photons along with one or more invisible particles. The resulting diphoton invariant mass signal is generically rather broad, as suggested by the data. We examine three specific event topologies - the antler, the sandwich, and the 2-step cascade decay, and show that they all can provide a good fit to the observed published data. In each case, we delineate the preferred mass parameter space selected by the best fit. In spite of the presence of invisible particles in the final state, the measured missing transverse energy is moderate, due to its anti- correlation with the diphoton invariant mass. We comment on the future prospects of discriminating with higher statistics between our scenarios, as well as from more conventional interpretations.

   hep-phhep-exPRL(2016)·123 citations
10. 10*

    LHC diphotons from electroweakly pair-produced composite pseudoscalars

    James M. Cline🇨🇦 · Zuowei Liu🇨🇳

    Motivated by excess diphoton events reported by ATLAS and CMS, we show that composite pseudoscalars, bound states of heavy fermions under a new confining gauge theory, can be pair-produced by Drell-Yan production if the constituent particles are electrically charged. The decays of these pion-like bound states into two photons can explain the observed events near 750 GeV. The model predicts that there should be significant numbers of 4-photon events from decays of the pseudoscalar pairs, as well as same-sign dilepton pairs at a somewhat lower invariant mass, or multijet signals, coming from decays of charge-2 pseudoscalars. These states and their decays are necessary for avoiding stable charged baryon-like relics in the new confining sector. A neutral baryon-like dark matter candidate of mass $\sim N_c\times 375$ GeV is a further prediction of the model, for SU($N_c$) confining gauge group.

    hep-ph104 citations
11. 11*

    Flavor Anomalies, the Diphoton Excess and a Dark Matter Candidate

    Martin Bauer🇩🇪 · Matthias Neubert🇩🇪

    We argue that the diphoton excess recently reported by ATLAS and CMS can be explained, along with several anomalies seen in the flavor sector, in models where a Standard-Model singlet scalar resonance with mass $M\approx 750$ GeV is produced in gluon fusion via loops containing a scalar color- triplet leptoquark $\varphi$. For a leptoquark mass $M_{\varphi }\lesssim$ 1 TeV, the production cross section is naturally in the 10 fb range. A large $S\to \gamma \gamma$ branching ratio can be obtained by coupling the scalar S to new color-singlet fermions $\chi$ with electroweak scale masses, which can be part of an $SU(2{)}_L$ multiplet, whose neutral component has the right mass and quantum numbers to be a dark matter candidate. Our model reveals a connection between flavor anomalies, the nature of dark matter and a new scalar, which acts as a mediator to the dark sector. The loop-mediated decay $S\to {\tau }^{+}{\tau }^{-}$ could be a striking signature of this model.

    hep-phPRD(2016)·140 citations
12. 12*

    Tricking Landau-Yang: How to obtain the diphoton excess from a vector resonance

    Mikael Chala🇩🇪 · Michael Duerr🇩🇪 · Felix Kahlhoefer🇩🇪 · Kai Schmidt-Hoberg🇩🇪

    We show that contrary to naive expectations the recently observed diphoton excess can be explained by a vector resonance, which decays to a photon and a light scalar $s$, followed by a decay of the scalar into two photons: $Z^{\prime }\to \gamma s\to 3\gamma$. As the two photons from the scalar decay are highly boosted, the experimental signature is an apparent diphoton final state. In fact all the necessary ingredients are naturally present in $Z^{\prime }$ models: Additional fermions with electroweak quantum numbers are required in order to render the theory anomaly free and naturally induce the required effective couplings, while the hidden Higgs which gives mass to the $Z^{\prime }$ can be very light. In particular no new coloured states are required in this framework. We also show that in such a setup the width of the resonance can be rather large, while all couplings remain perturbative.

    hep-phPLB(2016)·137 citations
13. 13*

    Extension of $\nu$MSM model and possible explanations of recent astronomical and collider observations

    Krishna Kulkarni🇮🇳

    Here I present the extension to $\nu$MSM model by adding a $U(1{)}^{\prime }$ gauge symmetry under which right-handed fermions including sterile neutrinos and exotic Higgs scalar are charged. This model explains 3.5 keV line observed by XMM-Newton telescope as well as Galactic Center Excess(GCE) detected by Fermi-LAT satellite. The proposed model also accounts for recent diphoton excess of mass around 750 GeV produced in ATLAS and CMS detectors. Cosmological inconsistencies such as baryon asymmetry can also be explained. Verification of presented model is possible with current experimental techniques and limitations. Careful validation and analysis of the model needs to be done in future.

    hep-ph29 citations
14. 14*

    One jet to rule them all: monojet constraints and invisible decays of a 750 GeV diphoton resonance

    Daniele Barducci🇫🇷 · Andreas Goudelis🇦🇹 · Suchita Kulkarni🇦🇹 · Dipan Sengupta🇫🇷

    The ATLAS and CMS collaborations recently reported a mild excess in the diphoton final state pointing to a resonance with a mass of around 750 GeV and a potentially large width. We consider the possibility of a scalar resonance being produced via gluon fusion and decaying to electroweak gauge bosons, jets and pairs of invisible particles, stable at collider scales. We compute limits from monojet searches on such a resonance and test their compatibility with the requirement for a large width. We also study whether the stable particle can be a a dark matter candidate and investigate the corresponding relic density constraints along with the collider limits. We show that monojet searches rule out a large part of the available parameter space and point out scenarios where a broad diphoton resonance can be reconciled with monojet constraints.

    hep-phhep-exJHEP(2016)·124 citations
15. 15*

    Jet fragmentation functions in proton-proton collisions using soft-collinear effective theory

    Yang-Ting Chien🇺🇸 · Zhong-Bo Kang🇺🇸 · Felix Ringer🇺🇸 · Ivan Vitev🇺🇸 · Hongxi Xing🇺🇸

    The jet fragmentation function describes the longitudinal momentum distribution of hadrons inside a reconstructed jet. We study the jet fragmentation function in proton-proton collisions in the framework of soft-collinear effective theory (SCET). We find that, up to power corrections, the jet fragmentation function can be expressed as the ratio of the fragmenting jet function and the unmeasured jet function. Using renormalization group techniques, we are able to resum large logarithms of jet radii R in the perturbative expansion of the cross section. We use our theoretical formalism to describe the jet fragmentation functions for light hadron and heavy meson production measured at the Large Hadron Collider (LHC). Our calculations agree very well with the experimental data for the light hadron production. On the other hand, although our calculations for the heavy meson production inside jets are consistent with the PYTHIA simulation, they fail to describe the LHC data. We find that the jet fragmentation function for heavy meson production is very sensitive to the gluon-to-heavy-meson fragmentation function.

    hep-phhep-exnucl-exnucl-thJHEP(2016)·75 citations
16. 16*

    Vector Dark Matter through a Radiative Higgs Portal

    Anthony DiFranzo🇺🇸 · Patrick J. Fox🇺🇸 · Tim M.P. Tait🇺🇸

    We study a model of spin-1 dark matter which interacts with the Standard Model predominantly via exchange of Higgs bosons. We propose an alternative UV completion to the usual Vector Dark Matter Higgs Portal, in which vector-like fermions charged under SU(2)${}_W\times$ U(1)${}_Y$ and under the dark gauge group, U(1)${}^{\prime }$, generate an effective interaction between the Higgs and the dark matter at one loop. We explore the resulting phenomenology and show that this dark matter candidate is a viable thermal relic and satisfies Higgs invisible width constraints as well as direct detection bounds.

    hep-phJHEP(2016)·52 citations
17. 17*

    Global Analyses of Neutrino Oscillation Experiments

    M.C. Gonzalez-Garcia🇪🇸 · Michele Maltoni🇪🇸 · Thomas Schwetz🇩🇪

    We summarize the determination of some neutrino properties from the global analysis of solar, atmospheric, reactor, and accelerator neutrino data in the framework of three-neutrino mixing as well as in some extended scenarios such as the mixing with eV-scale sterile neutrinos invoked for the interpretation of the short baseline anomalies, and the presence of non-standard neutrino interactions.

    hep-phastro-ph.SRhep-exNPB(2016)·230 citations
18. 18*

    Beyond Higgs Couplings: Probing the Higgs with Angular Observables at Future $e^{+}{e}^{-}$ Colliders

    Nathaniel Craig🇺🇸 · Jiayin Gu🇨🇳 · Zhen Liu🇺🇸 · Kechen Wang🇨🇳

    We study angular observables in the $e^{+}{e}^{-}\to ZH\to {\ell }^{+}{\ell }^{-}b\bar{b}$ channel at future circular $e^{+}{e}^{-}$ colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy $\sqrt{s}=$ 240 GeV and 5 (30) ${\mathrm{ab}}^{-1}$ integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgs-strahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementary sensitivity to rate measurements when constraining various tensor structures arising from new physics. We further find that angular asymmetries provide a novel means of both probing BSM corrections to the $HZ\gamma$ coupling and constraining the "blind spot" in indirect limits on supersymmetric scalar top partners.

    hep-phhep-exJHEP(2016)·56 citations
19. 19*

    The LHC diphoton resonance from gauge symmetry

    Sofiane M. Boucenna🇮🇹 · Stefano Morisi🇮🇹 · Avelino Vicente🇪🇸

    Motivated by what is possibly the first sign of new physics seen at the LHC, the diphoton excess at $750$ GeV in ATLAS and CMS, we present a model that provides naturally the necessary ingredients to explain the resonance. The simplest phenomenological explanation for the diphoton excess requires a new scalar state, $X(750)$, as well as additional vector-like (VL) fermions introduced in an ad-hoc way in order to enhance its decays into a pair of photons and/or increase its production cross-section. We show that the requiered VL quarks and their couplings can emerge naturally from a complete framework based on the $SU(3{)}_L\otimes U(1{)}_{\mathcal{X}}$ gauge symmetry.

    hep-phPRD(2016)·123 citations
20. 20*

    GENIE Production Release 2.10.0

    M. Alam🇮🇳 · C. Andreopoulos🇬🇧 · M. Athar🇮🇳 · A. Bodek🇺🇸 · E. Christy🇺🇸 · B. Coopersmith🇺🇸 · S. Dennis🇬🇧 · S. Dytman🇺🇸 · H. Gallagher🇺🇸 · N. Geary🇺🇸 · T. Golan🇵🇱 · R. Hatcher🇺🇸 and 9 other authors

    GENIE is a neutrino Monte Carlo event generator that simulates the primary interaction of a neutrino with a nuclear target, along with the subsequent propagation of the reaction products through the nuclear medium. It additionally contains libraries for fully-featured detector geometries and for managing various types of neutrino flux. This note details recent updates to GENIE, in particular changes introduced into the newest production release, version 2.10.0.

    hep-phhep-ex26 citations
21. 21*

    The quark susceptibility in a generalized dynamical quasiparticle model

    Hamza Berrehrah🇩🇪 · Wolfgang Cassing🇩🇪 · Elena Bratkovskaya🇩🇪 · Thorsten Steinert🇩🇪

    The quark susceptibility ${\chi }_q$ at zero and finite quark chemical potential provides a critical benchmark to determine the quark-gluon-plasma (QGP) degrees of freedom in relation to the results from lattice QCD (lQCD) in addition to the equation of state and transport coefficients. Here we extend the familiar dynamical-quasiparticle model (DQPM) to partonic propagators that explicitly depend on the three-momentum with respect to the partonic medium at rest in order to match perturbative QCD (pQCD) at high momenta. Within the extended dynamical-quasi-particle model (DQPM${}^{\ast }$) we reproduce simultaneously the lQCD results for the quark number density and susceptibility and the QGP pressure at zero and finite (but small) chemical potential ${\mu }_q$. The shear viscosity $\eta$ and the electric conductivity ${\sigma }_e$ from the extended quasiparticle model (DQPM${}^{\ast }$) also turn out in close agreement with lattice results for ${\mu }_q$ =0. The DQPM${}^{\ast }$, furthermore, allows to evaluate the momentum $p$, temperature $T$ and chemical potential ${\mu }_q$ dependencies of the partonic degrees of freedom also for larger ${\mu }_q$ which are mandatory for transport studies of heavy-ion collisions in the regime 5 GeV $<\sqrt{s_{NN}}<$ 10 GeV.

    hep-phnucl-thPRC(2016)·28 citations
22. 22*

    Flavor-Universal Form of Neutrino Oscillation Probabilities in Matter

    Hisakazu Minakata🇧🇷

    We construct a new perturbative framework to describe neutrino oscillation in matter with the unique expansion parameter \epsilon, which is defined as \Delta m^2_{21} / \Delta m^2_{ren} with the renormalized atmospheric \Delta m^2_{ren} \equiv \Delta m^2_{31} - s^2_{12} \Delta m^2_{21}. It allows us to derive the maximally compact expressions of the oscillation probabilities in matter to order \epsilon in the form akin to those in vacuum. This feature allows immediate physical interpretation of the formulas, and facilitates understanding of physics of neutrino oscillations in matter. Moreover, quite recently, we have shown that our three-flavor oscillation probabilities P(\nu_\alpha \rightarrow \nu_\beta) in all channels can be expressed in the form of universal functions of L/E. The \nu_e disappearance oscillation probability P(\nu_e \rightarrow \nu_e) has a special property that it can be written as the two-flavor form which depends on the single frequency. This talk is based on the collaborating work with Stephen Parke [1].

    hep-ph0 citations
23. 23*

    Photon and neutrino-pair emission from circulating quantum ions

    M. Yoshimura🇯🇵 · N. Sasao🇯🇵

    The recent proposal of photon and neutrino pair beam is extensively investigated. Production rates, both differential and total, of single photon, two-photon and neutrino-pair emitted from quantum ions in circular motion are calculated for any velocity of ion. This part is an extension of our previous results at highest energies to lower energies of circulating ions, and helps much to identify the new process at a low energy ion ring. We clarify how to utilize the circulating ion for a new source of coherent neutrino beam despite of much stronger background photons. Once one verifies that the coherence is maintained in the initial phases of time evolution after laser irradiation, large background photon emission rates are not an obstacle against utilizing the extracted neutrino pair beam.

    hep-phhep-exPRD(2016)·5 citations
24. 24*

    Vector Leptoquarks and the 750 GeV Diphoton Resonance at the LHC

    Christopher W. Murphy🇮🇹

    The ATLAS and CMS collaborations recently presented evidence of a resonance decaying to pairs of photons around 750 GeV. In addition, the BaBar, Belle, and LHCb collaborations have evidence of lepton non-universality in the semileptonic decays of $B$ mesons. In this work, we make a first step towards a unified explanation of these anomalies. Specifically, we extend the Standard Model by including vector leptoquarks and a scalar singlet that couples linearly to pairs of the leptoquarks. We find there is parameter space that gives the correct cross section for a putative 750 GeV resonance decaying to photons that is consistent with unitarity, measurements of the properties of the 125 GeV Higgs boson, and direct searches for resonances in other channels. In addition, we also show that constraints can be derived on any Beyond the Standard Model explanation of the 750 GeV resonance where the only new particles are scalars, which are strong enough to rule out certain types of models entirely.

    hep-phPLB(2016)·136 citations
25. 25*

    $E_6$ Inspired SUSY Benchmarks, Dark Matter Relic Density and a 125 GeV Higgs

    P. Athron (1)🇦🇺 · D. Harries (2)🇦🇺 · R. Nevzorov (2)🇦🇺 · A. G. Williams (2) ((1) Monash University, (2) University of Adelaide)🇦🇺

    We explore the relic density of dark matter and the particle spectrum within a constrained version of an $E_6$ inspired SUSY model with an extra $U(1{)}_N$ gauge symmetry. In this model a single exact custodial symmetry forbids tree-level flavor-changing transitions and the most dangerous baryon and lepton number violating operators. We present a set of benchmark points showing scenarios that have a SM-like Higgs mass of 125 GeV and sparticle masses above the LHC limits. They lead to striking new physics signatures which may be observed during run II of the LHC and can distinguish this model from the simplest SUSY extensions of the SM. At the same time these benchmark scenarios are consistent with the measured dark matter abundance and necessarily lead to large dark matter direct detection cross sections close to current limits and observable soon at the XENON1T experiment.

    hep-phPLB(2016)·44 citations
26. 26*

    Sudakov Resummations in Mueller-Navelet Dijet Production

    A. H. Mueller🇺🇸 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸

    In high energy hadron-hadron collisions, dijet production with large rapidity separation proposed by Mueller and Navelet, is one of the most interesting processes which can help us to directly access the well-known Balitsky-Fadin-Kuraev-Lipatov evolution dynamics. The objective of this work is to study the Sudakov resummation of Mueller-Navelet jets. Through the one-loop calculation, Sudakov type logarithms are obtained for this process when the produced dijets are almost back-to-back. These results could play an important role in the phenomenological study of dijet correlations with large rapidity separation at the LHC.

    hep-phnucl-thJHEP(2016)·55 citations
27. 27*

    Chiral methods at the electroweak scale

    Oscar Cata🇩🇪

    I review the main features of the effective field theory (EFT) behind scenarios of dynamical electroweak symmetry breaking, placing particular emphasis on the systematics and the parallels that can be drawn with Chiral Perturbation Theory. The notion of chiral dimensions will be introduced and shown to be the right tool to describe nonlinear expansions. I will also discuss why such an EFT is of interest in phenomenological studies at the LHC. The most important aspect is that the EFT is engineered to recover the Standard Model in a particular limit, and therefore provides a general framework to test the Higgs hypothesis. Additionally, I will argue that the $\kappa$ formalism used currently by experimental collaborations to study Higgs couplings at the LHC can actually be embedded into this EFT. This not only gives the $\kappa$ parametrization a solid QFT foundation but also shows the way to improve it systematically, and in particular how to upgrade analyses on Higgs processes from the level of rates to the level of distributions.

    hep-phPoS(2015)·0 citations
28. 28*

    Baryon octet distribution amplitudes in Wandzura-Wilczek approximation

    I.V. Anikin🇷🇺 · A.N. Manashov🇩🇪

    We study higher twist distribution amplitudes for the SU_F(3) baryon octet. We identify independent functions for all baryons in the isospin symmetry limit and calculate the Wandzura-Wilczek contributions to the twist-4 and 5 distributions amplitudes.

    hep-phPRD(2016)·5 citations
29. 29*

    $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ decays at large recoil in the Standard Model: a theoretical reappraisal

    Marco Ciuchini🇮🇹 · Marco Fedele🇮🇹 · Enrico Franco🇮🇹 · Satoshi Mishima🇯🇵 · Ayan Paul🇮🇹 · Luca Silvestrini🇮🇹 · Mauro Valli🇮🇹

    We critically reassess the theoretical uncertainties in the Standard Model calculation of the $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$ observables, focusing on the low $q^2$ region. We point out that even optimized observables are affected by sizable uncertainties, since hadronic contributions generated by current-current operators with charm are difficult to estimate, especially for $q^2\sim 4m_c^2\simeq 6.8$ GeV${}^2$. We perform a detailed numerical analysis and present both predictions and results from the fit obtained using most recent data. We find that non-factorizable power corrections of the expected order of magnitude are sufficient to give a good description of current experimental data within the Standard Model. We discuss in detail the $q^2$ dependence of the corrections and their possible interpretation as shifts of the Standard Model Wilson coefficients.

    hep-phJHEP(2016)·285 citations
30. 30*

    LHC diphoton 750 GeV resonance as an indication of $SU(3{)}_c\times SU(3{)}_L\times U(1{)}_X$ gauge symmetry

    A. E. Cárcamo Hernández🇨🇱 · Ivan Nisandzic🇩🇪

    The LHC collaborations ATLAS and CMS recently reported on the excess of the events in the diphoton final states at the invariant mass of about $750\text{GeV}$. In this article we speculate on the possibility that the excess arises from the neutral CP-even component $\varphi$ of the scalar triplet $\Phi$ of the $SU(3{)}_c\times SU(3{)}_L\times U(1{)}_X$ $(3\text{-}3\text{-}1)$ model that has a $U(1{)}_X$ charge equal to $X=-1/3$ and acquires a vacuum expectation value larger than the electroweak symmetry breaking scale. The interactions of the scalar field $\varphi$ to the photon- and gluon-pairs are mediated by the virtual vector-like fermions which appear as components of the anomaly-free chiral fermion representations of the $3\text{ -}3\text{-}1$ gauge group.

    hep-phEPJC(2016)·124 citations
31. 31*

    $B_{s,d}^{\ast }\to {\mu }^{+}{\mu }^{-}$ and its impact on $B_{s,d}\to {\mu }^{+}{\mu }^{-}$

    Guang-Zhi Xu🇨🇳 · Yue Qiu🇨🇳 · Cheng-Ping Shen🇨🇳 · Yu-Jie Zhang🇨🇳

    The decay of $B_{s,d}^{\ast }\to {\mu }^{+}{\mu }^{-}$~ and its impact on $B_{s,d}\to {\mu }^{+}{\mu }^{-}$ is studied here. The ${\mu }^{+}{\mu }^{-}$ decay widths of vector mesons $B_{s,d}^{\ast }$ are about a factor of 700 larger than the corresponding scalar mesons $B_{s,d}$. The obtained ratio of the branching fractions $Br(B_{s,d}^{\ast }\to {\mu }^{+}{\mu }^{-})/Br(B_{s,d}\to {\mu }^{+}{\mu }^{-})$ is about $\frac{0.3\times \mathrm{eV}}{\Gamma (B_{s,d}^{\ast }\to B_{s,d}\gamma )}$. At the same time, the hadronic contribution $B_{s,d}\to B_{s,d}^{\ast }\gamma \to {\mu }^{+}{\mu }^{-}$ is estimated too. The relative increase of the amplitude of $B_{s,d}\to {\mu }^{+}{\mu }^{-}$ is about $(0.01\pm 0.006)\sqrt{\frac{\Gamma (B_{s,d}^{\ast }\to B_{s,d}\gamma )}{100\mathrm{eV}}}$. If we choose $\Gamma (B_{s,d}^{\ast }\to B_{s,d}\gamma )=2$eV, the branching fractions of the vector mesons to lepton pair are $(6.2\pm 0.6)\times 10^{-10}$ and $(1.7\pm 0.2)\times 10^{-11}$ for $B_s^{\ast }$ and $B_d^{\ast }$ respectively. If we choose $\Gamma (B_{s,d}^{\ast }\to B_{s,d}\gamma )=200$eV, the updated branching fractions of the scalar mesons to muon pair are $(3.78\pm 0.25)\times 10^{-9}$ and $(1.09\pm 0.09)\times 10^{-10}$ for $B_s$ and $B_d$ respectively. Further studies on $B_{s,d}^{\ast }$ are usefully here, including dielectron decay, two-body decay with $J/\psi$, and so on.

    hep-phEPJC(2016)·18 citations
32. 32*

    Transverse spin azimuthal asymmetries at COMPASS: SIDIS Multi-D analysis & Drell-Yan

    Bakur Parsamyan🇮🇹

    COMPASS is a high-energy physics experiment operating on the M2 beam line at the SPS at CERN. Using high energy muon and hadron beams the experiment covers broad range of physics aspects in the field of the hadron structure and spectroscopy. One of the important objectives of the COMPASS experiment is the exploration of transverse spin structure of the nucleon via study of spin (in)dependent azimuthal asymmetries with semi-inclusive deep inelastic scattering (SIDIS) processes and starting from 2014 also with Drell-Yan (DY) reactions. Experimental results obtained by COMPASS for azimuthal effects in SIDIS play an important role in the general understanding of the three-dimensional nature of the nucleon. Giving access to the entire "twist-2" set of transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FFs) COMPASS data trigger constant theoretical interest and are being widely used in phenomenological analyses and global data fits. In particular, unique x-$Q^2$-z-pT multidimensional results for transverse spin asymmetries recently obtained by COMPASS will serve as a direct and unprecedented input for TMD $Q^2$-evolution related studies, one of the hottest topics in the field of spin-physics. In addition, measurement of the Sivers and all other azimuthal effects in polarized Drell-Yan at COMPASS will reveal another side of the spin-puzzle providing a link between SIDIS and Drell-Yan branches. This will be a unique possibility to test universality and key-features of TMD PDFs using essentially the same experimental setup and exploring the same kinematical domain. In this review main focus will be given to the very recent results obtained by the collaboration for multi-dimensional transverse spin asymmetries and to the physics aspects of COMPASS polarized Drell-Yan program.

    ↳ hep-exhep-ph2 citations
33. 33*

    Dark matter-radiation interactions: the structure of Milky Way satellite galaxies

    J. A. Schewtschenko🇬🇧 · C. M. Baugh🇬🇧 · R. J. Wilkinson🇬🇧 · C. Boehm🇬🇧 · S. Pascoli🇬🇧 · T. Sawala🇫🇮

    In the thermal dark matter (DM) paradigm, primordial interactions between DM and Standard Model particles are responsible for the observed DM relic density. In Boehm et al. (2014), we showed that weak-strength interactions between DM and radiation (photons or neutrinos) can erase small-scale density fluctuations, leading to a suppression of the matter power spectrum compared to the collisionless cold DM (CDM) model. This results in fewer DM subhaloes within Milky Way-like DM haloes, implying a reduction in the abundance of satellite galaxies. Here we use very high resolution N-body simulations to measure the dynamics of these subhaloes. We find that when interactions are included, the largest subhaloes are less concentrated than their counterparts in the collisionless CDM model and have rotation curves that match observational data, providing a new solution to the "too big to fail" problem.

    ↳ astro-ph.COhep-phMNRAS(2016)·79 citations
34. 34*

    Radio detection prospects for a bulge population of millisecond pulsars as suggested by Fermi LAT observations of the inner Galaxy

    Francesca Calore🇳🇱 · Mattia Di Mauro🇺🇸 · Fiorenza Donato🇮🇹 · Jason W.T. Hessels🇳🇱 · Christoph Weniger🇳🇱

    Analogously to globular clusters, the dense stellar environment of the Galactic center has been proposed to host a large population of as-yet undetected millisecond pulsars (MSPs). Recently, this hypothesis found support in the analysis of gamma rays from the inner Galaxy seen by the Large Area Telescope (LAT) aboard the Fermi satellite, which revealed a possible excess of diffuse GeV photons in the inner 15 deg about the Galactic center (Fermi GeV excess). The excess can be interpreted as the collective emission of thousands of MSPs in the Galactic bulge, with a spherical distribution that strongly peaks towards the Galactic center. In order to fully establish the MSP interpretation, it is essential to find corroborating evidence in multi-wavelength searches, most notably through the detection of radio pulsation from individual bulge MSPs. Based on globular cluster observations and the gamma-ray emission from the inner Galaxy, we investigate the prospects for detecting MSPs in the Galactic bulge. While previous pulsar surveys failed to identify this population, we demonstrate that, in the upcoming years, new large-area surveys with focus on regions a few degrees north or south of the Galactic center should lead to the detection of dozens of bulge MSPs. Additionally, we show that, in the near future, deep targeted searches of unassociated Fermi sources should be able to detect the first few MSPs in the bulge. The prospects for these deep searches are enhanced by a tentative gamma-ray/radio correlation that we infer from high-latitude gamma-ray MSPs. Such detections would constitute the first clear discoveries of field MSPs in the Galactic bulge, with far-reaching implications for gamma-ray observations, the formation history of the central Milky Way and strategy optimization for future radio observations.

    ↳ astro-ph.HEhep-phApJ(2016)·108 citations
35. 35*

    Electromagnetic and gravitational radiation from massless particles

    D.V. Gal'tsov🇷🇺

    We demonstrate that full description of both electromagnetic and gravitational radiation from massless particles lies outside the scope of classical theory. Synchrotron radiation from the hypothetical massless charge in quantum electrodynamics in external magnetic field has finite total power while the corresponding classical formula diverges in the massless limit. We argue that in both cases classical theory describes correctly only the low-frequency part of the spectra, while the total power diverges because of absence of the UV frequency cutoff. Failure of description of gravitational radiation from massless particles by classical General Relativity may be considered as another appeal for quantization of gravity apart from the problem of singularities.

    ↳ hep-thastro-ph.HEgr-qchep-ph0 citations
36. 36*

    On the EFT of Large Scale Structures in Redshift Space

    Matthew Lewandowski🇺🇸 · Leonardo Senatore🇺🇸 · Francisco Prada🇪🇸 · Cheng Zhao🇨🇳 · Chia-Hsun Chuang🇪🇸

    We further develop the description of redshift space distortions within the Effective Field Theory of Large Scale Structures. First, we generalize the counterterms to include the effect of baryonic physics and primordial non-Gaussianity. Second, we evaluate the IR-resummation of the dark matter power spectrum in redshift space. This requires us to identify a controlled approximation that makes the numerical evaluation straightforward and efficient. Third, we compare the predictions of the theory at one loop with the power spectrum from numerical simulations up to $\ell =6$. We find that the IR-resummation allows us to correctly reproduce the BAO peak. The $k$-reach, or equivalently the precision for a given $k$, depends on additional counterterms that need to be matched to simulations. Since the non-linear scale for the velocity is expected to be longer than the one for the overdensity, we consider a minimal and a non-minimal set of counterterms. The quality of our numerical data makes it hard to firmly establish the performance of the theory at high wavenumbers. Within this limitation, we find that the theory at redshift $z=0.56$ and up to $\ell =2$ matches the data to percent level approximately up to $k\sim 0.13h\mathrm{Mp}{\mathrm{c}}^{-1}$ or $k\sim 0.18h\mathrm{Mp}{\mathrm{c}}^{-1}$, depending on the number of counterterms used, with potentially large improvement over former analytical techniques.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·112 citations
37. 37*

    Non-compact nonlinear sigma models

    Claudia de Rham🇺🇸 · Andrew J. Tolley🇺🇸 · Shuang-Yong Zhou🇺🇸

    The target space of a nonlinear sigma model is usually required to be positive definite to avoid ghosts. We introduce a unique class of nonlinear sigma models where the target space metric has a Lorentzian signature, thus the associated group being non-compact. We show that the would-be ghost associated with the negative direction is fully projected out by 2 second-class constraints, and there exist stable solutions in this class of models. This result also has important implications for Lorentz--invariant massive gravity: There exist stable nontrivial vacua in massive gravity that are free from any linear vDVZ--discontinuity and a ${\Lambda }_2$ decoupling limit can be defined on these vacua.

    ↳ hep-thastro-ph.COgr-qchep-phPLB(2016)·29 citations
38. 38*

    Standard Model in multiscale theories and observational constraints

    Gianluca Calcagni🇪🇸 · Giuseppe Nardelli🇮🇹 · David Rodríguez-Fernández🇪🇸

    We construct and analyze the Standard Model of electroweak and strong interactions in multiscale spacetimes with (i) weighted derivatives and (ii) $q$-derivatives. Both theories can be formulated in two different frames, called fractional and integer picture. By definition, the fractional picture is where physical predictions should be made. (i) In the theory with weighted derivatives, it is shown that gauge invariance and the requirement of having constant masses in all reference frames make the Standard Model in the integer picture indistinguishable from the ordinary one. Experiments involving only weak and strong forces are insensitive to a change of spacetime dimensionality also in the fractional picture, and only the electromagnetic and gravitational sectors can break the degeneracy. For the simplest multiscale measures with only one characteristic time, length and energy scale $t_{\ast }$, ${\ell }_{\ast }$ and $E_{\ast }$, we compute the Lamb shift in the hydrogen atom and constrain the multiscale correction to the ordinary result, getting the absolute upper bound $t_{\ast }<10^{-23}\mathrm{s}$. For the natural choice ${\alpha }_0=1/2$ of the fractional exponent in the measure, this bound is strengthened to $t_{\ast }<10^{-29}\mathrm{s}$, corresponding to ${\ell }_{\ast }<10^{-20}\mathrm{m}$ and $E_{\ast }>28\mathrm{TeV}$. Stronger bounds are obtained from the measurement of the fine-structure constant. (ii) In the theory with $q$-derivatives, considering the muon decay rate and the Lamb shift in light atoms, we obtain the independent absolute upper bounds $t_{\ast }<10^{-13}\mathrm{s}$ and $E_{\ast }>35\text{MeV}$. For ${\alpha }_0=1/2$, the Lamb shift alone yields $t_{\ast }<10^{-27}\mathrm{s}$, ${\ell }_{\ast }<10^{-19}\mathrm{m}$ and $E_{\ast }>450\text{GeV}$.

    ↳ hep-thhep-phPRD(2016)·21 citations
39. 39*

    Non-equilibrium dynamics and phase transitions

    Romuald A. Janik🇵🇱 · Jakub Jankowski🇵🇱 · Hesam Soltanpanahi🇵🇱

    We study the poles of the retarded Green's functions of strongly coupled field theories exhibiting a variety of phase structures from a crossover up to a first order phase transition. These theories are modeled by a dual gravitational description. The poles of the holographic Green's functions appear at the frequencies of the quasinormal modes of the dual black hole background. We establish that near the transition, in all cases considered, the applicability of a hydrodynamic description breaks down already at lower momenta than in the conformal case. We establish the appearance of the spinodal region in the case of the first order phase transition at temperatures for which the speed of sound squared is negative. An estimate of the preferential scale attained by the unstable modes is also given. We additionally observe a novel diffusive regime for sound modes for a range of wavelengths.

    ↳ hep-thhep-phPRL(2016)·44 citations
40. 40*

    Conserved Charge Fluctuations from Lattice QCD and the Beam Energy Scan

    F. Karsch🇩🇪 · A. Bazavov🇺🇸 · H.-T. Ding🇨🇳 · P. Hegde🇨🇳 · O. Kaczmarek🇩🇪 · E. Laermann🇩🇪 · Swagato Mukherjee🇺🇸 · H. Ohno🇺🇸 · P. Petreczky🇺🇸 · C. Schmidt🇩🇪 · S. Sharma🇺🇸 · W. Soeldner🇩🇪 · P. Steinbrecher🇩🇪 · M. Wagner🇺🇸

    We discuss the next-to-leading order Taylor expansion of ratios of cumulants of net-baryon number fluctuations. We focus on the relation between the skewness ratio, $S_B{\sigma }_B={\chi }_3^B/{\chi }_1^B$, and the kurtosis ratio, ${\kappa }_B{\sigma }_B^2={\chi }_4^B/{\chi }_2^B$. We show that differences in these two cumulant ratios are small for small values of the baryon chemical potential. The next-to-leading order correction to ${\kappa }_B{\sigma }_B^2$ however is approximately three times larger than that for $S_B{\sigma }_B$. The former thus drops much more rapidly with increasing beam energy, $\sqrt{s_{NN}}$. We argue that these generic patterns are consistent with current data on cumulants of net-proton number fluctuations measured by the STAR Collaboration at $\sqrt{s_{NN}}\ge 19.6$~GeV.

    ↳ hep-lathep-phNPA(2016)·28 citations
41. 41*

    The unreasonable effectiveness of hydrodynamics in heavy ion collisions

    Jacquelyn Noronha-Hostler🇺🇸 · Jorge Noronha🇧🇷 · Miklos Gyulassy🇺🇸

    Event-by-event hydrodynamic simulations of AA and pA collisions involve initial energy densities with large spatial gradients. This is associated with the presence of large Knudsen numbers ($K_n\approx 1$) at early times, which may lead one to question the validity of the hydrodynamic approach in these rapidly evolving, largely inhomogeneous systems. A new procedure to smooth out the initial energy densities is employed to show that the initial spatial eccentricities, ${\epsilon }_n$, are remarkably robust with respect to variations in the underlying scale of initial energy density spatial gradients, $\lambda$. For $\sqrt{s_{NN}}=2.76$ TeV LHC initial conditions generated by the MCKLN code, ${\epsilon }_n$ (across centralities) remains nearly constant if the fluctuation scale varies by an order of magnitude, i.e., when $\lambda$ varies from 0.1 to 1 fm. Given that the local Knudsen number $K_n\approx \frac{1}{\lambda }$, the robustness of the initial eccentricities with respect to changes in the fluctuation scale suggests that the vn's cannot be used to distinguish between events with large $K_n$ from events where $K_n$ is in the hydrodynamic regime. We use the 2+1 Lagrangian hydrodynamic code v-USPhydro to show that this is indeed the case: anisotropic flow coefficients computed within event-by-event viscous hydrodynamics are only sensitive to long wavelength scales of order $\frac{1}{{\Lambda }_{QCD}}\approx 1$ fm and are incredibly robust with respect to variations in the initial local Knudsen number. This robustness can be used to justify the somewhat unreasonable effectiveness of the nearly perfect fluid paradigm in heavy ion collisions.

    ↳ nucl-thhep-phNPA(2016)·18 citations
42. 42*

    Long wavelength perfect fluidity from short distance jet transport in quark-gluon plasmas

    Jiechen Xu🇺🇸 · Jinfeng Liao🇺🇸 · Miklos Gyulassy🇺🇸

    We build a new phenomenological framework that bridges the long wavelength bulk viscous transport properties of the strongly-coupled quark-gluon plasma (sQGP) and short distance hard jet transport properties in the QGP. The full nonperturbative chromo-electric (E) and chromo-magnetic (M) structure of the near "perfect fluid" like sQGP in the critical transition region are integrated into a semi-Quark-Gluon-Monopole Plasma (sQGMP) model lattice-compatibly and implemented into the new CUJET3.0 jet quenching framework. All observables computed from CUJET3.0 are found to be consistent with available data at RHIC and LHC simultaneously. A quantitative connection between the shear viscosity and jet transport parameter is rigorously established within this framework. We deduce the $T=160-600$ MeV dependence of the QGP's $\eta /s$: its near vanishing value in the near $T_c$ regime is determined by the composition of E and M charges, it increases as $T$ rises, and its high $T$ limit is fixed by color screening scales.

    ↳ nucl-thhep-phnucl-exNPA(2016)·0 citations
43. 43*

    Could reggeon field theory be an effective theory for QCD in the Regge limit?

    Jochen Bartels🇩🇪 · Carlos Contreras🇨🇱 · Gian Paolo Vacca🇮🇹

    In this paper we investigate the possibility whether, in the extreme limit of high energies and large transverse distances, reggeon field theory might serve as an effective theory of high energy scattering for strong interactions. We analyse the functional renormalization group equations (flow equations) of reggeon field theory and search for fixed points in the space of (local) reggeon field theories. We study in complementary ways the candidate for the scaling solution, investigate its main properties and briefly discuss possible physical interpretations.

    ↳ hep-thhep-phJHEP(2016)·23 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.