HEP Phenomenology·hep-ph
21 papers—17 primary·4 cross-listed·reconstructed*
Rajiv Gavai🇮🇳 · Ambar Jain🇮🇳 · Rishi Sharma🇮🇳
We propose a new observable, called zeal, to analyze events with jets in heavy ion collisions. The observable measures how a thermal medium affects the multiplicity and distribution of energetic particles in a jet. Using few known models for energy loss and jet quenching, we demonstrate its capability to distinguish the physics of these models.
Joaquín Santos🇪🇸 · Ignasi Rosell🇪🇸 · Antonio Pich🇪🇸 · Juan José Sanz-Cillero🇪🇸
As a first step towards the construction of a general electroweak effective Lagrangian incorporating heavy states, we present here a simplified version where only vector and axial-vector spin-1 triplets are involved. We adopt an effective field theory formalism, implementing the electroweak chiral symmetry breaking SU(2)L x SU(2)R -> SU(2)L+R, which couples the heavy states to the SM fields. At low energies, the heavy degrees of freedom are integrated out from the action and their effects are hidden in the low-energy couplings of the Electroweak Effective Theory, which can be tested experimentally. Short-distance constraints are also implemented, requiring a proper behaviour in the high-energy regime. We analyze the phenomenological constraints from the oblique parameters S and T , at the next- to-leading order. Our results show that present data allow for strongly-coupled scenarios with massive bosons above the TeV scale.
Antonio Dobado🇪🇸 · Rafael L. Delgado🇪🇸 · Felipe J. Llanes-Estrada🇪🇸
If new resonances of the electroweak symmetry breaking sector (longitudinal-gauge and Higgs) bosons are found in the 1-3 TeV region, the right tool to assess their properties and confront experimental data in a largely model-independent yet simple manner is Unitarized Effective Theory. Its ingredients are: 1) custodial symmetry and the Equivalence Theorem, that allow to approximate W_L and Z_L by an isospin-triplet of Goldstone bosons omega^a in the 1-TeV region. 2) The effective coupling of a generic, approximately massless scalar-isoscalar h to those Goldstone bosons, and the chiral Lagrangian describing them, valid up to about 3 TeV. 3) The Inverse Amplitude or other unitarization techniques that allow to extend the reach of perturbation theory to the first resonance in each partial wave. We highlight some of the parameter space that can give rise to 2-TeV resonances, for example a simultaneous scalar-isoscalar and a vector-isovector ones (motivated by the ATLAS excess) and also the potential importance of coupled-channel dynamics between hh and omega omega.
Eduardo C. Andrés🇦🇷 · Leandro Da Rold🇦🇷 · Iván A. Davidovich🇦🇷
We consider one of the most significant deviations from the Standard Model: the forward-backward asymmetry of the b-quark measured at leptonic colliders. We investigate the possibility to solve this discrepancy by introducing new physics at the TeV scale. We focus on models where the Higgs is a pseudo Nambu-Goldstone boson of a new strongly coupled sector with a global SO(5) symmetry broken spontaneously to SO(4). Besides the usual top partners, we introduce bottom partners in the representations 16 and 4 of SO(5) and show that they can improve significantly the fit by correcting the Zbb couplings. We also estimate the corrections to the couplings at one-loop and obtain that the tree-level ones dominate and can give a reliable estimation. We find that the large shift required for Zb_Rb_R leads to light custodians associated to the b-quark, similar to the top partners, as well as a rich phenomenology involving neutral interactions in the bottom-sector.
N. Ghahramany🇮🇷 · A. R. Houshyar🇮🇷
The rare semileptonic decay is analyzed, by using the three-point QCD sum rules. Taking into account the two-gluon condensate contributions, the transition form factors related to this decay are calculated and are used to determine the total decay width and branching fraction. Our findings may be approved by future experiments.
Sahar Bahrami🇨🇦 · Mariana Frank🇨🇦
We analyze the effects of introducing vector-like leptons in the Higgs Triplet Model providing the lightest vector-like neutrino as a Dark Matter candidate. We explore the effect of the relic density constraint on the mass and Yukawa coupling of dark matter, as well as calculate the cross sections for indirect and direct dark matter detection. We show our model predictions for the neutrino and muon fluxes from the Sun, and the restrictions they impose on the parameter space. We show that this model, with a restricted parameter space, is completely consistent with dark matter constraints, and indicate the resulting mass region for the dark matter.
I review TMD factorization and evolution theorems, with an emphasis on the treatment by Collins and originating in the Collins-Soper-Sterman (CSS) formalism. I summarize basic results while attempting to trace their development over that past several decades.
We study the charmed meson pair ( and ) production in annihilation within an effective Lagrangian model that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction amplitudes include terms corresponding to the t-channel , and baryon exchanges and the s-channel excitation, propagation and decay of the (3770) resonance into the charmed mesons. The initial- and final-state distortion effects have been accounted for by using a simple eikonal approximation-based procedure in the same way as was done in our previous study of the reaction within a similar model. The production reaction is dominated by the baryon exchange process, and the corresponding total cross sections are predicted to be in the range of 0.18 - 0.7 b for antiproton beam momenta varying between threshold and 20 . The (3770) resonance contributions have a large influence on the differential cross sections of the production reaction.
J.D. Gomez🇧🇷 · A.A. Natale🇧🇷
We consider the electron-positron annihilation process into hadrons up to and we adopt the smearing method suggest by Poggio, Quinn and Weinberg to confront the experimental data with theory. As a theoretical model we use a QCD coupling constant frozen in the low energy regime, where this coupling can be parameterised in terms of an effective dynamical gluon mass () which is determined through Schwinger-Dyson equations. In order to find the best fit between experimental data and theory we perform a study, that, within the uncertainties of the approach, has a minimum value when is in the range . These values are in agreement with other phenomenological determinations of this ratio and lead to an infrared effective charge . We comment how this effective charge may affect the global duality mass scale that indicates the frontier between perturbative and non-perturbative physics.
Shigeru Odaka🇯🇵 · Yoshimasa Kurihara🇯🇵
We have developed an event generator for direct-photon production in hadron collisions, including associated two-jet production in the framework of the GR@PPA event generator. The event generator consistently combines + 2-jet production processes with the lowest-order + jet and photon-radiation (fragmentation) processes from QCD 2-jet production using a subtraction method. The generated events can be fed to general-purpose event generators to facilitate the addition of hadronization and decay simulations. Using the obtained event information, we can simulate photon isolation and hadron-jet reconstruction at the particle (hadron) level. The simulation reasonably reproduces measurement data obtained at the LHC concerning not only the inclusive photon spectrum, but also the correlation between the photon and jet. The simulation implies that the contribution of the + 2-jet is very large, especially in low photon- ( 50 GeV) regions. Discrepancies observed at low , although marginal, may indicate the necessity for the consideration of further higher-order processes. Unambiguous particle-level definition of the photon-isolation condition for the signal events is desired to be given explicitly in future measurements.
K. Hasegawa🇯🇵 · C.S. Lim🇯🇵 · Nobuhito Maru🇯🇵
In the gauge-Higgs unification with multiple extra spaces, the Higgs self-coupling is of the order of and Higgs is predicted to be light, being consistent with the LHC results. When the gauge group is simple, the weak mixing angle is also predictable. We address a question whether there exists a model of gauge-Higgs unification in 6-dimensional space-time, which successfully predicts the mass ratios of the Higgs boson and weak gauge bosons. First, by use of a useful formula we give a general argument on the condition to get a realistic prediction of the weak mixing angle , and find that triplet and sextet representations of the minimal SU(3) gauge group lead to the realistic prediction. Concerning the Higgs mass, we notice that in the models with one Higgs doublet, the predicted Higgs mass is always the same: . However, by extending our discussion to the models with two Higgs doublets, the situation changes: we obtain an interesting prediction at the leading order of the perturbation. Thus it is possible to recover the observed Higgs mass, 125 GeV, for a suitable choice of the parameter. The situation is in clear contrast to the case of the minimal supersymmetric standard model, where at the classical level and the predicted Higgs mass cannot recover the observed value.
Benjamin Grinstein🇺🇸 · Richard F. Lebed🇺🇸
The model-independent parametrization for exclusive hadronic form factors commonly used for semileptonic decays is generalized to allow for the inclusion of above-threshold resonant poles of known mass and width. We discuss the interpretation of such poles, particularly with respect to the analytic structure of the relevant two-point Green's function in which they reside. Their presence has a remarkably small effect on the parametrization, as we show explicitly for the case of .
B. Ducloué🇫🇮 · T. Lappi🇫🇮 · H. Mäntysaari🇫🇮
We re-evaluate the nuclear suppression of forward production at high energy in the Color Glass Condensate framework. We use the collinear approximation for the projectile proton probed at large and an up to date dipole cross section fitted to HERA data to describe the target in proton-proton collisions. We show that using the Glauber approach to generalize the proton dipole cross section to the case of a nucleus target leads to a nuclear modification factor much closer to LHC data than previous estimates using the same framework.
V.V. Anisovich🇷🇺 · M.A. Matveev🇷🇺 · J. Nyiri🇭🇺 · A.V. Sarantsev🇩🇪 · A.N. Semenova🇷🇺
Non-strange and strange pentaquaks with hidden charm are considered as diquark-diquark-antiquark composite systems. Spin and isospin content of such exotic states is discussed and masses are evaluated.
Yasuhiro Shimizu🇯🇵 · Wen Yin🇯🇵
We suggest a natural split mechanism for sfermions based on =2 supersymmetry (SUSY). =2 SUSY protects a sfermion in an =2 multiplet from gaining weight by SUSY breaking. Therefore, if partly =2 SUSY is effectively obtained, a split spectrum can be realized naturally. As an example of the natural split mechanism, we build a gauge-mediated SUSY breaking-like model assuming =2 SUSY is partly broken in a UV theory. The model explains the Higgs boson mass and the muon anomalous magnetic dipole moment within level with a splitting sfermion spectrum. The model has seven light sparticles described by three free parameters and predicts a new chiral multiplet, sb: the =2 partner of the vector multiplet. The bini, the fermion component of the sb, weighs MeVs. We mention the experimental and the cosmological aspects of the model.
P. Bicudo🇵🇹 · M. Cardoso🇵🇹
We address exotic tetraquark bound states and resonances with a fully unitarized and microscopic quark model. We propose a triple string flip-flop potential, inspired in lattice QCD tetraquarks static potentials and fluxtubes, combining meson-meson and tetraquark potentials. Our potential goes up to the color excited potential, but neglects spin-tensor potentials. To search for bound states and resonances, we first solve the two-body mesonic problem. Then we develop fully unitary techniques to address the four-body tetraquark problem. We fold the four-body Shcrödinger equation with the mesonic wavefunctions, transforming it into a two-body meson-meson problem with non-local potentials. We find bound states for some quark masses numbers, including the one reported in lattice QCD. Moreover, we also find resonances and calculate their masses and widths, by computing the matrix and finding it's pole positions in the complex energy plane, for some quantum numbers. However a detailed analysis of the quantum numbers where binding exists shows a discrepancy with recent lattice QCD results for the tetraquark bound states. We conclude that the string flip-flop models need further improvement.
In gluon fusion both a modified top Yukawa and new colored particles can alter the cross section. However in a large set of composite Higgs models and in realistic areas of the MSSM parameter space, these two effects can conspire and hide new physics in a Standard Model-like inclusive cross section. We first show that it is possible to break this degeneracy in the couplings by demanding a boosted Higgs recoiling against a high- jet. Subsequently we propose an analysis based on this idea in the channels. This measurement allows an alternative determination of the important top Yukawa besides the channel.
Shinsuke Kawai🇰🇷 · Yu Nakayama🇺🇸
Assuming gauge/gravity correspondence we study reheating of the Universe using its holographic dual. Inflaton decay and thermalisation of the decay products correspond to collapse of a spherical shell and formation of a blackhole in the dual anti-de Sitter (AdS) spacetime. The reheating temperature is computed as the Hawking temperature of the developed blackhole probed by a dynamical boundary, and is determined by the inflaton energy density and the AdS radius, with corrections from the dynamics of the shell collapse. For given initial energy density of the inflaton field the holographic model gives significantly lower reheating temperature than the instant reheating scenario, while it is shown to be safely within phenomenological bounds.
J.C. Hardy🇺🇸 · I.S. Towner🇺🇸
The Vud element of the Cabibbo-Kobayashi-Maskawa matrix can be determined from several different experimental approaches: either 0+-to-0+ superallowed nuclear beta decays, neutron decay, nuclear mirror decays, or pion beta decay. Currently all give consistent results but, because the nuclear superallowed value has an uncertainty at least a factor of seven less than all other results, it dominates the result. A new survey of world superallowed-decay data establishes the Ft values of 14 separate superallowed transitions to a precision of order 0.1% or better; and all 14 are statistically consistent with one another. This very robust data set yields the result Vud = 0.97417(21), the value we recommend.
Mihajlo Kornicer (for the BESIII collaboration)🇺🇸
Several states that couple to one light-meson and a heavy-charmonium are recently reported, including the and . These states cannot be interpreted within the constituent quark-model of mesons, and are good candidates for a new form of quark matter, four-quark matter. A review of recent results on new charmonium-like states studied at BESIII is presented.
Ryutaro Matsudo🇯🇵 · Kei-Ichi Kondo🇯🇵
We give a gauge-independent definition of magnetic monopoles in the Yang-Mills theory through the Wilson loop operator. For this purpose, we give an explicit proof of the Diakonov-Petrov version of the non-Abelian Stokes theorem for the Wilson loop operator in an arbitrary representation of the gauge group to derive a new form for the non-Abelian Stokes theorem. The new form is used to extract the magnetic-monopole contribution to the Wilson loop operator in a gauge-invariant way, which enables us to discuss confinement of quarks in any representation from the viewpoint of the dual superconductor vacuum.
* 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.