PaperPanorama

HEP Phenomenology·hep-ph

Mon·May 23, 2016

26 papers15 primary·11 cross-listed·reconstructed*

  1. 01*

    Direct Search Implications for a Custodially-Embedded Composite Top

    R. Sekhar Chivukula🇺🇸 · Roshan Foadi🇫🇮 · Dennis Foren🇺🇸 · Elizabeth H. Simmons🇺🇸

    We assess current experimental constraints on the bi-doublet + singlet model of top compositeness previously proposed in the literature. This model extends the standard model's spectrum by adding a custodially-embedded vector-like electroweak bi-doublet of quarks and a vector-like electroweak singlet quark. While either of those states alone would produce a model in tension with constraints from precision electroweak data, in combination they can produce a viable model. We show that current precision electroweak data, in the wake of the Higgs discovery, accommodate the model and we explore the impact of direct collider searches for the partners of the top quark.

    hep-phPRD(2016)·0 citations
  2. 02*

    Higgs lepton flavour violation: UV completions and connection to neutrino masses

    Juan Herrero-Garcia🇸🇪 · Nuria Rius🇪🇸 · Arcadi Santamaria🇪🇸

    We study lepton violating Higgs (HLFV) decays, first from the effective field theory (EFT) point of view, and then analysing the different high-energy realizations of the operators of the EFT, highlighting the most promising models. We argue why two Higgs doublet models can have a , and why this rate is suppressed in all other realizations including vector-like leptons. We further discuss HLFV in the context of neutrino mass models: in most cases it is generated at one loop giving always and typically much less, which is beyond experimental reach. However, both the Zee model and extended left-right symmetric models contain extra doublets coupled to leptons and could in principle account for the observed excess, with interesting connections between HLFV and neutrino parameters.

    hep-phJHEP(2016)·58 citations
  3. 03*

    Running vacuum in the Universe and the time variation of the fundamental constants of Nature

    Harald Fritzsch🇩🇪 · Joan Sola🇪🇸 · Rafael C. Nunes🇧🇷

    We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newton's constant) within the context of the so-called running vacuum models (RVM's) of the cosmic evolution. Recently, compelling evidence has been provided showing that these models are able to fit the main cosmological data (SNIa+BAO+H(z)+LSS+BBN+CMB) significantly better than the concordance CDM model. Specifically, the vacuum parameters of the RVM (i.e. those responsible for the dynamics of the vacuum energy) prove to be nonzero at a confidence level . Here we use such remarkable status of the RVM's to make definite predictions on the cosmic time variation of the fundamental constants. It turns out that the predicted variations are close to the present observational limits. Furthermore, we find that the time variation of the dark matter particles should be crucially involved in the total mass variation of our Universe. A positive measurement of this kind of effects could be interpreted as strong support to the "micro and macro connection" (viz. the dynamical feedback between the evolution of the cosmological parameters and the time variation of the fundamental constants of the microscopic world), previously proposed by two of us (HF and JS).

    hep-phastro-ph.COgr-qchep-thEPJC(2017)·69 citations
  4. 04*

    Exploiting jet binning to identify the initial state of high-mass resonances

    Markus A. Ebert🇩🇪 · Stefan Liebler🇩🇪 · Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Kerstin Tackmann🇩🇪 · Lisa Zeune🇳🇱

    If a new high-mass resonance is discovered at the Large Hadron Collider, model-independent techniques to identify the production mechanism will be crucial to understand its nature and effective couplings to Standard Model particles. We present a powerful and model-independent method to infer the initial state in the production of any high-mass color-singlet system by using a tight veto on accompanying hadronic jets to divide the data into two mutually exclusive event samples (jet bins). For a resonance of several hundred GeV, the jet binning cut needed to discriminate quark and gluon initial states is in the experimentally accessible range of several tens of GeV. It also yields comparable cross sections for both bins, making this method viable already with the small event samples available shortly after a discovery. Theoretically, the method is made feasible by utilizing an effective field theory setup to compute the jet cut dependence precisely and model independently and to systematically control all sources of theoretical uncertainties in the jet binning, as well as their correlations. We use a 750 GeV scalar resonance as an example to demonstrate the viability of our method.

    hep-phhep-exPRD(2016)·29 citations
  5. 05*

    Singlet-Catalyzed Electroweak Phase Transitions in the 100 TeV Frontier

    Ashutosh V. Kotwal🇺🇸 · Michael J. Ramsey-Musolf🇺🇸 · Jose Miguel No🇬🇧 · Peter Winslow🇺🇸

    We study the prospects for probing a gauge singlet scalar-driven strong first order electroweak phase transition with a future proton-proton collider in the 100 TeV range. Singlet-Higgs mixing enables resonantly-enhanced di-Higgs production, potentially aiding discovery prospects. We perform Monte Carlo scans of the parameter space to identify regions associated with a strong first-order electroweak phase transition, analyze the corresponding di-Higgs signal, and select a set of benchmark points that span the range of di-Higgs signal strengths. For the and final states, we investigate discovery prospects for each benchmark point for the high luminosity phase of the Large Hadron Collider and for a future collider with = 50, 100, or 200 TeV. We find that any of these future collider scenarios could significantly extend the reach beyond that of the high luminosity LHC, and that with = 100 TeV (200 TeV) and 30 ab, the full region of parameter space favorable to strong first order electroweak phase transitions is almost fully (fully) discoverable.

    hep-phPRD(2016)·116 citations
  6. 06*

    Vincia for Hadron Colliders

    Nadine Fischer🇦🇺 · Stefan Prestel🇺🇸 · Mathias Ritzmann🇳🇱 · Peter Skands🇦🇺

    We present the first public implementation of antenna-based QCD initial- and final-state showers. The shower kernels are antenna functions, which capture not only the collinear dynamics but also the leading soft (coherent) singularities of QCD matrix elements. We define the evolution measure to be inversely proportional to the leading poles, hence gluon emissions are evolved in a measure inversely proportional to the eikonal, while processes that only contain a single pole (e.g., ) are evolved in virtuality. Non-ordered emissions are allowed, suppressed by an additional power of . Recoils and kinematics are governed by exact on-shell phase-space factorisations. This first implementation is limited to massless QCD partons and colourless resonances. Tree-level matrix-element corrections are included for QCD up to (4 jets), and for Drell-Yan and Higgs production up to ( + 3 jets). The resulting algorithm has been made publicly available in Vincia 2.0.

    hep-phEPJC(2016)·116 citations
  7. 07*

    Employing Helicity Amplitudes for Resummation in SCET

    Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Wouter J. Waalewijn🇳🇱

    Helicity amplitudes are the fundamental ingredients of many QCD calculations for multi-leg processes. We describe how these can seamlessly be combined with resummation in Soft-Collinear Effective Theory (SCET), by constructing a helicity operator basis for which the Wilson coefficients are directly given in terms of color-ordered helicity amplitudes. This basis is crossing symmetric and has simple transformation properties under discrete symmetries.

    hep-phnucl-th2 citations
  8. 08*

    Few remarks on the Higgs boson decays in gauge-Higgs unification

    K. Hasegawa🇯🇵 · C. S. Lim🇯🇵

    In the scenario of gauge-Higgs unification, the origin of the Higgs boson is higher dimensional gauge boson. Reflecting its origin, very characteristic predictions are made of the Higgs boson interactions in this scenario. Especially, a remarkable claim has been made: the contribution of non-zero Kaluza-Klein modes to the Higgs decay exactly vanishes in the minimal SU(3) electro-weak unified model, at least at the one-loop level. In this brief report, in order to see whether this prediction is a general feature of the scenario or the consequence of the specific choice of the model, matter content or the order of perturbative expansion, we perform an operator analysis. We demonstrate that there does not exist any relevant operator, respecting the gauge symmetry SU(3) in the bulk. We also comment on the possibly important contribution to the photonic decay due to the non-zero Kaluza-Klein modes of light quarks.

    hep-phPRD(2016)·5 citations
  9. 09*

    Leptonic Precision Test of Leptophilic Two-Higgs-Doublet Model

    Eung Jin Chun🇰🇷 · Jinsu Kim🇰🇷

    The type X (lepton-specific) two-Higgs-doublet model at large becomes leptophilic and thus allows a light pseudoscalar accommodating the observed muon deviation without conflicting with various hadronic constraints. On the other hand, it is strongly constrained by leptonic precision observables such as lepton universality test in the neutral and charged currents. Treating all the lepton universality data in a consistent way, we show how the current data constrain the parameter space of and for given degenerate masses of heavy Higgs bosons and . While no overlapping region is found at , a sizable region is still viable at for masses at around 200400 GeV.

    hep-phJHEP(2016)·92 citations
  10. 10*

    in a strongly coupled QFT

    Namit Mahajan🇮🇳

    We consider theory with the coupling being large, and calculate shear viscosity to entropy density ratio (). The final result for has a form remarkably similar to that obtained from string theory calculations via the AdS/CFT conjecture. The method adopted can be used to compute quantities of interest in other theories as well with some modifications and reveals some very interesting features within the considered theory.

    hep-phhep-th1 citation
  11. 11*

    Towards a unified explanation of , and anomalies in a left-right model with leptoquarks

    Diganta Das🇮🇳 · Chandan Hati🇮🇳 · Girish Kumar🇮🇳 · Namit Mahajan🇮🇳

    We present a unified explanation for the -decay anomalies in and together with the anomalous muon magnetic moment, consistent with the constraints from the current measurements of leptonic decay rates and , mixings, within the framework of a minimal left-right symmetric gauge theory motivated by one of the low-energy subgroups of naturally accommodating leptoquarks.

    hep-phPRD(2016)·158 citations
  12. 12*

    Multi-Higgs production in gluon fusion at 100 TeV

    Celine Degrande🇬🇧 · Valentin V. Khoze🇬🇧 · Olivier Mattelaer🇬🇧

    We carry out a detailed study of multi-Higgs production processes in the gluon fusion channel in the high energy regime relevant to Future Circular hadron colliders and in the high-Higgs-multiplicity limit (> 20). Our results are based on the computation of the leading polygons - the triangles, boxes, pentagons and hexagons - to the scattering processes, further combined with the subsequent branchings to reach high final state multiplicities. The factorial growth of the number of diagrams leads to an exponential enhancement of such large multiplicity cross-sections and, ultimately, in breaking of perturbativity. We find that the characteristic energy and multiplicity scales where these perturbative rates become highly enhanced and grow with increasing energy are within the 100 TeV regime with of the order of 130 Higgses (or more) in the final state. We also show that already for a 50 TeV hadron collider the perturbative cross-sections for 140 bosons are at picobarn level.

    hep-phPRD(2016)·21 citations
  13. 13*

    Non-linear Higgs portal to Dark Matter

    Rocío del Rey Bajo🇪🇸

    The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the interactions of gauge bosons and the physical Higgs particle to a scalar singlet Dark Matter candidate in an effective description. The main phenomenological differences with respect to the standard scenario can be seen in the Dark Matter relic abundance, in direct/indirect searches and in signals at colliders.

    hep-ph1 citation
  14. 14*

    Note on predictions for quarkonia using a three-loop static potential

    Noah Green🇺🇸 · Wayne W. Repko🇺🇸 · Stanley F. Radford🇺🇸

    We extend our treatment of the the spectroscopy and decays of the charm-strange quarkonium system to include the effect of using the full three-loop QCD correction to the static short distance potential. As before, our potential model consists of the relativistic kinetic energy term, a scalar linear confining term including its relativistic corrections and the perturbative QCD spin-dependent terms. A set of unperturbed wave functions for the various states is obtained using a variational technique that is further constrained by requiring that the wave functions also satisfy the relativistic virial theorem. These are then used in a perturbative treatment of the potential to fit the mass spectrum of the system and calculate the radiative decay widths. Our results accurately describe the spectrum and are compatible with the little data that is available for the radiative decays of the states.

    hep-phNPA(2017)·11 citations
  15. 15*

    Accuracy and Precision in Collider Event Shapes

    Daniel W. Kolodrubetz🇺🇸

    In this thesis, we discuss and investigate the use of Soft-Collinear Effective Theory (SCET) for high precision calculations. In the first part of the work, we present an extraction of the strong coupling, and the leading nonperturbative parameter , using the event shape C-parameter. By comparing lepton collider data to the C-parameter cross section, we extract values and with for bins of data. The later parts of this thesis are dedicated to using on-shell helicity methods to extend SCET beyond leading power. We present a complete set of scalar helicity building blocks and describe an interesting angular momentum selection rule that restricts how these building blocks can be assembled.

    hep-ph2 citations
  16. 16*

    The fate of non-polynomial interactions in scalar field theory

    I. Hamzaan Bridle🇬🇧 · Tim R. Morris🇬🇧

    We present an exact RG (renormalization group) analysis of -invariant scalar field theory about the Gaussian fixed point. We prove a series of statements that taken together show that the non-polynomial eigen-perturbations found in the LPA (local potential approximation) at the linearised level, do not lead to new interactions, \textit{i.e.} enlarge the universality class, neither in the LPA or treated exactly. Non-perturbatively, their RG flow does not emanate from the fixed point. For the equivalent Wilsonian effective action they can be re-expressed in terms of the usual couplings to polynomial interactions, which can furthermore be tuned to be as small as desired for all finite RG time. For the infrared cutoff Legendre effective action, this can also be done for the infrared evolution. We explain why this is nevertheless consistent with the fact that the large field behaviour is fixed by these perturbations.

    hep-thcond-mat.stat-mechhep-phPRD(2016)·28 citations
  17. 17*

    A New Approach to Non-Abelian Hydrodynamics

    Jose J. Fernandez-Melgarejo🇺🇸 · Soo-Jong Rey🇰🇷 · Piotr Surówka🇺🇸

    We present a new approach to describe hydrodynamics carrying non-Abelian macroscopic degrees of freedom. Based on the Kaluza-Klein compactification of a higher-dimensional neutral dissipative fluid on a group manifold, we obtain a d=4 colored dissipative fluid coupled to Yang-Mills gauge field. We calculate the transport coefficients of the new fluid, which show the non-Abelian character of the gauge group. In particular, we obtain group-valued terms in the gradient expansions and response quantities such as the conductivity matrix and the chemical potentials. While using SU(2) for simplicity, this approach is applicable to any gauge group. Resulting a robust description of non-Abelian hydrodynamics, we discuss some links between this system and quark-gluon plasma and fluid/gravity duality.

    hep-thcond-mat.str-elhep-phJHEP(2017)·10 citations
  18. 18*

    hi_class: Horndeski in the Cosmic Linear Anisotropy Solving System

    Miguel Zumalacarregui🇸🇪 · Emilio Bellini🇪🇸 · Ignacy Sawicki🇨🇿 · Julien Lesgourgues🇩🇪 · Pedro G. Ferreira🇬🇧

    We present the public version of hi_class (www.hiclass-code.net), an extension of the Boltzmann code CLASS to a broad ensemble of modifications to general relativity. In particular, hi_class can calculate predictions for models based on Horndeski's theory, which is the most general scalar-tensor theory described by second-order equations of motion and encompasses any perfect-fluid dark energy, quintessence, Brans-Dicke, and covariant Galileon models. hi_class has been thoroughly tested and can be readily used to understand the impact of alternative theories of gravity on linear structure formation as well as for cosmological parameter extraction.

    astro-ph.COgr-qchep-phhep-thJCAP(2017)·243 citations
  19. 19*

    Softness and Amplitudes' Positivity for Spinning Particles

    Brando Bellazzini🇫🇷

    We derive positivity bounds for scattering amplitudes of particles with arbitrary spin using unitarity, analyticity and crossing symmetry. The bounds imply the positivity of certain low-energy coefficients of the effective action that controls the dynamics of the light degrees of freedom. We show that low-energy amplitudes strictly softer than do not admit unitary ultraviolet completions unless the theory is free. This enforces a bound on the energy growth of scattering amplitudes in the region of validity of the effective theory. We discuss explicit examples including the Goldstino from spontaneous supersymmetry breaking, and the theory of a spin-1/2 fermion with a shift symmetry.

    hep-thhep-phJHEP(2017)·201 citations
  20. 20*

    High Energy Neutrinos from Recent Blazar Flares

    Francis Halzen🇺🇸 · Ali Kheirandish🇺🇸

    The energy density of cosmic neutrinos measured by IceCube matches the one observed by Fermi in extragalactic photons that predominantly originate in blazars. This has inspired attempts to match Fermi sources with IceCube neutrinos. A spatial association combined with a coincidence in time with a flaring source may represent a smoking gun for the origin of the IceCube flux. In June 2015, the Fermi Large Area Telescope observed an intense flare from blazar 3C 279 that exceeded the steady flux of the source by a factor of forty for the duration of a day. We show that IceCube is likely to observe neutrinos, if indeed hadronic in origin, in data that are still blinded at this time. We also discuss other opportunities for coincident observations that include a recent flare from blazar 1ES 1959+650 that previously produced an intriguing coincidence with AMANDA observations.

    astro-ph.HEhep-phApJ(2016)·28 citations
  21. 21*

    Cosmological backreaction in higher-derivative gravity expansions

    Anthony W. H. Preston🇬🇧

    We calculate a general effective stress-energy tensor induced by cosmological inhomogeneity in effective theories of gravity where the action is Taylor-expandable in the Riemann tensor and covariant derivatives of the Riemann tensor. This is of interest as an effective fluid that might provide an alternative to the cosmological constant, but it also applies to gravitational waves. We use an adaptation of Green and Wald's weak-averaging framework, which averages over perturbations in the field equation where the perturbation length scales are small compared to the averaging scale. In this adaptation, the length scale of the effective theory, , is also taken to be small compared with the averaging scale. This ensures that the perturbation length scales remain in fixed proportion to the length scale of the effective theory as the cosmological averaging scale is taken to be large. We find that backreaction from higher-derivative terms in the effective action can continue to be important in the late universe, given a source of sufficiently high-frequency metric perturbations. This backreaction might also provide a window on exotic particle physics in the far ultraviolet.

    gr-qcastro-ph.COhep-phhep-thJCAP(2016)·9 citations
  22. 22*

    A low-mass dark matter search using ionization signals in XENON100

    XENON100 Collaboration: E. Aprile · J. Aalbers · F. Agostini · M. Alfonsi · F. D. Amaro · M. Anthony · F. Arneodo · P. Barrow · L. Baudis · B. Bauermeister · M. L. Benabderrahmane · T. Berger and 98 other authors

    We perform a low-mass dark matter search using an exposure of 30\,kgyr with the XENON100 detector. By dropping the requirement of a scintillation signal and using only the ionization signal to determine the interaction energy, we lowered the energy threshold for detection to 0.7\,keV for nuclear recoils. No dark matter detection can be claimed because a complete background model cannot be constructed without a primary scintillation signal. Instead, we compute an upper limit on the WIMP-nucleon scattering cross section under the assumption that every event passing our selection criteria could be a signal event. Using an energy interval from 0.7\,keV to 9.1\,keV, we derive a limit on the spin-independent WIMP-nucleon cross section that excludes WIMPs with a mass of 6\,GeV/ above \,cm at 90\% confidence level.

    astro-ph.COhep-exhep-phphysics.ins-detPRD(2016)·183 citations
  23. 23*

    Reheating in Gauss-Bonnet-coupled inflation

    Carsten van de Bruck🇬🇧 · Konstantinos Dimopoulos🇬🇧 · Chris Longden🇬🇧

    We investigate the feasibility of models of inflation with a large Gauss-Bonnet coupling at late times, which have been shown to modify and prevent the end of inflation. Despite the potential of Gauss-Bonnet models in predicting favourable power spectra, capable of greatly lowering the tensor-to-scalar-ratio compared to now-disfavoured models of standard chaotic inflation, it is important to also understand in what context it is possible for post-inflationary (p)reheating to proceed and hence recover an acceptable late-time cosmology. We argue that in the previously-studied inverse power law coupling case, reheating cannot happen due to a lack of oscillatory solutions for the inflaton, and that neither instant preheating nor gravitational particle production would avoid this problem due to the persistence of the inflaton's energy density, even if it were to partially decay. Hence we proceed to define a minimal generalisation of the model which can permit perturbative reheating and study the consequences of this, including heavily modified dynamics during reheating and predictions of the power spectra.

    astro-ph.COgr-qchep-phhep-thPRD(2016)·79 citations
  24. 24*

    Probing inflation models with gravitational waves

    Valerie Domcke🇫🇷

    A direct detection of primordial gravitational waves is the ultimate probe for any inflation model. While current CMB bounds predict the generic scale-invariant gravitational wave spectrum from slow-roll inflation to be below the reach of upcoming gravitational wave interferometers, this prospect may dramatically change if the inflaton is a pseudoscalar. In this case, a coupling to any abelian gauge field leads to a tachyonic instability for the latter and hence to a new source of gravitational waves, directly related to the dynamics of inflation. In this contribution we discuss how this setup enables the upcoming gravitational wave interferometers advanced LIGO/VIRGO and eLISA to probe the microphysics of inflation, distinguishing between different universality classes of single-field slow-roll inflation models. We find that the prime candidate for an early detection is a Starobinsky-like model.

    astro-ph.COhep-ph3 citations
  25. 25*

    Deciphering the Dipole Anisotropy of Galactic Cosmic Rays

    Markus Ahlers🇺🇸

    Recent measurements of the dipole anisotropy in the arrival directions of Galactic cosmic rays (CRs) indicate a strong energy dependence of the dipole amplitude and phase in the TeV-PeV range. We argue here that these observations can be well understood within standard diffusion theory as a combined effect of (i) one or more local sources at Galactic longitude 120deg < l < 300deg dominating the CR gradient below 0.1-0.3 PeV, (ii) the presence of a strong ordered magnetic field in our local environment, (iii) the relative motion of the solar system, and (iv) the limited reconstruction capabilities of ground-based observatories. We show that an excellent candidate of the local CR source responsible for the dipole anisotropy at 1-100 TeV is the Vela supernova remnant.

    astro-ph.HEhep-exhep-phPRL(2016)·87 citations
  26. 26*

    Linearized Boltzmann transport model for jet propagation in the quark-gluon plasma: Heavy quark evolution

    Shanshan Cao🇺🇸 · Tan Luo🇨🇳 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳

    A Linearized Boltzmann Transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the meson suppression and elliptic flow observed at the LHC and RHIC. The prediction for the Pb-Pb collisions at =5.02~TeV is provided.

    nucl-thhep-phnucl-exPRC(2016)·314 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.