HEP Phenomenology·hep-ph
24 papers—17 primary·7 cross-listed·reconstructed*
Jambul Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪 · Dmitrij Siemens🇩🇪 · De-Liang Yao🇩🇪
We calculate the width of the delta resonance at leading two-loop order in baryon chiral perturbation theory. This gives a correlation between the leading pion-nucleon-delta and pion-delta couplings, which is relevant for the analysis of pion-nucleon scattering and other processes.
P. Kotko🇺🇸 · A.M. Stasto🇺🇸 · M. Strikman🇺🇸
The crucial parameter of the current Monte Carlo models of high energy hadron-hadron interaction is the transverse momentum cutoff for parton-parton interactions which slowly grows with energy and regularizes the cross section. This modification of the collinear factorization formula goes beyond the leading power and thus a natural question arises if such cutoff can be extracted from a formalism which takes into account power corrections. In this work, we consider the High Energy Factorization (HEF) valid at small and a new model, based on a similar principle to HEF, which in addition has a limit respecting the Dokshitzer-Dyakonov-Troyan formula for the dijet momentum disbalance spectrum. Minijet cross section and its suppression is then analyzed in two ways. First, we study minijets directly in the low- region, and demonstrate that higher twist corrections do generate suppression of the inclusive jet production cross section though these effects are not leading to the increase of the cutoff with incident energy. Second, we consider hard inclusive dijet production where Multi Parton Interactions (MPIs) with minijets produce power corrections. We introduce an observable constructed from differential cross section in the ratio of dijet disbalance to the average dijet and demonstrate that the region is sensitive to the cutoff in the MPI minijet models. The energy dependence of the cutoff is reflected in the energy dependence of the bimodality coefficient of the distribution. We compare calculated from , where one can conveniently control MPIs by the program parameters, and HEF for a few unintegrated gluon distributions (UGDs). We find that the energy dependence of is very sensitive to the particular choice of UGD and in some models it resembles predictions of the Monte Carlo models.
Kaustubh Agashe🇺🇸 · Peizhi Du🇺🇸 · Sungwoo Hong🇺🇸 · Raman Sundrum🇺🇸
Warped higher-dimensional compactifications with "bulk" standard model, or their AdS/CFT dual as the purely 4D scenario of Higgs compositeness and partial compositeness, offer an elegant approach to resolving the electroweak hierarchy problem as well as the origins of flavor structure. However, low-energy electroweak/flavor/CP constraints and the absence of non-standard physics at LHC Run 1 suggest that a "little hierarchy problem" remains, and that the new physics underlying naturalness may lie out of LHC reach. Assuming this to be the case, we show that there is a simple and natural extension of the minimal warped model in the Randall-Sundrum framework, in which matter, gauge and gravitational fields propagate modestly different degrees into the IR of the warped dimension, resulting in rich and striking consequences for the LHC (and beyond). The LHC-accessible part of the new physics is AdS/CFT dual to the mechanism of "vectorlike confinement", with TeV-scale Kaluza-Klein excitations of the gauge and gravitational fields dual to spin-0,1,2 composites. Unlike the minimal warped model, these low-lying excitations have predominantly flavor-blind and flavor/CP-safe interactions with the standard model. Remarkably, this scenario also predicts small deviations from flavor-blindness originating from virtual effects of Higgs/top compositeness at TeV, with subdominant resonance decays into Higgs/top-rich final states, giving the LHC an early "preview" of the nature of the resolution of the hierarchy problem. Discoveries of this type at LHC Run 2 would thereby anticipate (and set a target for) even more explicit explorations of Higgs compositeness at a 100 TeV collider, or for next-generation flavor tests.
Stefan Berge🇩🇪 · Susanne Westhoff🇩🇪
The top-antitop energy asymmetry is a promising observable of the charge asymmetry in jet-associated top-quark pair production at the LHC. We present new predictions of the energy asymmetry in proton-proton collisions at 13 TeV, including QCD corrections at the next-to-leading perturbative order. The effect of QCD corrections on the observable is moderate. With suitable phase-space cuts, the asymmetry can be enhanced at the cost of reducing the cross section. For instance, for a cross section of after cuts, we predict an energy asymmetry of at the next-to-leading order in QCD. We also investigate scale uncertainties and parton-shower effects, which partially cancel in the normalized asymmetry. Our results provide a sound basis for a measurement of the energy asymmetry at the LHC during run II.
Manfred Lindner🇩🇪 · Alexander Merle🇩🇪 · Moritz Platscher🇩🇪 · Carlos E. Yaguna🇩🇪
We demonstrate that the condition of vacuum stability severely restricts scenarios with fermionic WIMP dark matter in the scotogenic model. The sizable Yukawa couplings that are required to satisfy the dark matter constraint via thermal freeze-out in these scenarios tend to destabilise the vacuum at scales below that of the heaviest singlet fermion, rendering the model inconsistent from a theoretical point of view. By means of a scan over the parameter space, we study the impact of these renormalisation group effects on the viable regions of this model. Our analysis shows that a fraction of more than 90% of the points compatible with all known experimental constraints - including neutrino masses, the dark matter density, and lepton flavour violation - is actually inconsistent.
Andrey Katz🇨🇭 · Antonio Riotto🇨🇭
We propose a novel mechanism for production of baryonic asymmetry in the early Universe. The mechanism takes advantage of the strong first order phase transition that produces runaway bubbles in the hidden sector that propagate almost without friction with ultra-relativistic velocities. Collisions of such bubbles can non-thermally produce heavy particles that further decay out-of-equilibrium into the SM and produce the observed baryonic asymmetry. This process can proceed at the very low temperatures, providing a new mechanism of post-sphaleron baryogenesis. In this paper we present a fully calculable model which produces the baryonic asymmetry along these lines as well as evades all the existing cosmological constraints. We emphasize that the Gravitational Waves signal from the first order phase transition is completely generic and can potentially be detected by the future eLISA interferometer. We also discuss other potential signals, which are more model dependent, and point out the unresolved theoretical questions related to our proposal.
D. A. Fogaça🇧🇷 · S. M. Sanches Jr.🇧🇷 · T. F. Motta🇧🇷 · F. S. Navarra🇧🇷
Some time ago we have derived from the QCD Lagrangian an equation of state (EOS) for the cold quark matter, which can be considered an improved version of the MIT bag model EOS. Compared to the latter, our equation of state reaches higher values of the pressure at comparable baryon densities. This feature is due to perturbative corrections and also to non-perturbative effects. Later we applied this EOS to the study of compact stars, discussing the absolute stability of quark matter and computing the mass-radius relation for self-bound (strange) stars. We found maximum masses of the sequences with more than two solar masses, in agreement with the recent experimental observations. In the present work we include the magnetic field in the equation of state and study how it changes the stability conditions and the mass-radius curves.
Philip Bechtle🇩🇪 · Howard E. Haber🇺🇸 · Sven Heinemeyer🇪🇸 · Oscar Stål🇸🇪 · Tim Stefaniak🇺🇸 · Georg Weiglein🇩🇪 · Lisa Zeune🇳🇱
We perform a parameter scan of the phenomenological Minimal Supersymmetric Standard Model (pMSSM) with eight parameters taking into account the experimental Higgs boson results from Run I of the LHC and further low-energy observables. We investigate various MSSM interpretations of the Higgs signal at 125 GeV. First, we consider the case where the light CP-even Higgs boson of the MSSM is identified with the discovered Higgs boson. In this case it can impersonate the SM Higgs-like signal either in the decoupling limit, or in the limit of alignment without decoupling. In the latter case, the other states in the Higgs sector can also be light, offering good prospects for upcoming LHC searches and for searches at future colliders. Second, we demonstrate that the heavy CP-even Higgs boson is still a viable candidate to explain the Higgs signal - albeit only in a highly constrained parameter region, that will be probed by LHC searches for the CP-odd Higgs boson and the charged Higgs boson in the near future. As a guidance for such searches we provide new benchmark scenarios that can be employed to maximize the sensitivity of the experimental analysis to this interpretation.
Pearl Sandick🇺🇸 · Kuver Sinha🇺🇸 · Fei Teng🇺🇸
We consider direct detection prospects for a class of simplified models of fermionic dark matter (DM) coupled to left and right-handed Standard Model fermions via two charged scalar mediators with arbitrary mixing angle . DM interactions with the nucleus are mediated by higher electromagnetic moments, which, for Majorana DM, is the anapole moment. After giving a full analytic calculation of the anapole moment, including its dependence, and matching with limits in the literature, we compute the DM-nucleon scattering cross-section and show the LUX and future LZ constraints on the parameter space of these models. We then compare these results with constraints coming from -LAT continuum and line searches. Results in the supersymmetric limit of these simplified models are provided in all cases. We find that future direct detection experiments will be able to probe most of the parameter space of these models for GeV DM and lightest mediator mass larger than the DM mass. The direct detection prospects dwindle for larger DM mass and larger mass gap between the DM and the lightest mediator mass, although appreciable regions are still probed for GeV DM and lightest mediator mass larger than the DM mass. The direct detection bounds are also attenuated near certain "blind spots" in the parameter space, where the anapole moment is severely suppressed due to cancellation of different terms. We carefully study these blind spots and the associated -LAT signals in these regions.
Radovan Dermisek🇺🇸 · Enrico Lunghi🇺🇸 · Seodong Shin🇺🇸
One of the cleanest signatures of a heavy Higgs boson in models with vectorlike leptons is which, in two Higgs doublet model type-II, can even be the dominant decay mode of heavy Higgses. Among the decay modes of the standard model like Higgs boson, , we consider and as representative channels with sizable and negligible background, respectively. We obtained new model independent limits on production cross section for this process from recasting existing experimental searches and interpret them within the two Higgs doublet model. In addition, we show that these limits can be improved by about two orders of magnitude with appropriate selection cuts immediately with existing data sets. We also discuss expected sensitivities with integrated luminosity up to 3 ab and present a brief overview of other channels.
Michal Czakon🇩🇪 · David Heymes🇬🇧 · Alexander Mitov🇬🇧
We demonstrate that a purposefully normalised NNLO top pair invariant mass differential spectrum can have very small theoretical uncertainty and, in particular, a small sensitivity to the top quark mass. Such observable can thus be a very effective bump-hunting tool for resonances decaying to top pair events during LHC Run II and beyond. To illustrate how the approach works, we concentrate on one specific example of current interest, namely, the possible 750 GeV di-gamma excess resonance Phi. Considering only theoretical uncertainties, we demonstrate that it is possible to distinguish pp -> Phi -> tt signals studied in the recent literature [Hespel, Maltoni and Vryonidou, arXiv:1606.04149] from the pure SM background with very high significance. Alternatively, in case of non-observation, a strong upper limit on the decay rate Phi -> tt can be placed.
J. Armando Arroyo🇲🇽 · Saul Ramos-Sanchez🇲🇽
Models endowed with Higgs portals can probe into the hidden sectors of particle physics while providing stable dark matter candidates. Previous tree-level computations in such scenarios have shown that experimental bounds constrain dark matter to a very narrow region in parameter space. Aiming at improving the study of the implications of those constraints, we inspect one-loop corrections to the annihilation cross section for scalar dark matter into observable fermions. We find that these loop contributions might be enough to drastically change those results by deforming in about 10% the allowed parameter space for dark matter particles with masses even below 1 TeV. These findings encourage further investigation.
B. R. Ko🇰🇷 · H. Themann🇺🇸 · W. Jang🇰🇷 · J. Choi🇰🇷 · D. Kim🇰🇷 · M. J. Lee🇰🇷 · J. Lee · E. Won🇰🇷 · Y. K. Semertzidis🇰🇷
We review a recent letter published in Phys. Rev. Lett. , 161804 (2016) of which the main argument is that the mode dependent magnetic form factors at axion haloscopes depend on the position of the cavity inside the solenoid while the corresponding electric form factors do not. We, however, find no such dependence, which is also equivalent to the statement that the electric and corresponding magnetic energy stored in the cavity modes are the same regardless of the position of the cavity inside the solenoid. Furthermore, we extend the statement to the cases satisfying , where is a static magnetic field provided by a magnet at an axion haloscope. Two typical magnets, solenoidal and toroidal, satisfy , thus the electric and corresponding magnetic energy stored in the cavity modes are always the same in both cases. The energy, however, is independent of the position of the cavity in axion haloscopes with a solenoid, but depends on those with a toroidal magnet.
Tseh Liou🇺🇸 · A. H. Mueller🇺🇸 · S. Munier🇫🇷
We address the general features of event-by-event fluctuations of the multiplicity of gluons produced in the scattering of a dilute hadron off a large nucleus at high energy in the fragmentation region of the dilute hadron. We relate these fluctuations to the stochasticity of the number of quanta contained in the hadron at the time of the interaction. For simplicity, we address the ideal case in which the hadron is an onium, and investigate different kinematical regimes in rapidity and onium size. We show that at large rapidity, the multiplicity distribution exhibits an exponential tail in the large-multiplicity region, which is qualitatively consistent with the proton-nucleus data. But interestingly enough, the exponential shape is determined by confinement.
Tanumoy Mandal🇸🇪 · Prashanth Jaikumar🇺🇸
We investigate the effect of turning on temperature for the charge neutral phase of two-flavor color superconducting (2SC) dense quark matter in presence of constant external magnetic field. Within the Nambu-Jona-Lasinio model, by tuning the diquark coupling strength, we study the interdependent evolution of the quark Bardeen-Cooper-Schrieffer gap and dynamical mass as functions of temperature and magnetic field. We find that magnetic field GeV ( G) leads to anomalous temperature behavior of the gap in the gapless 2SC phase (moderately strong coupling), reminiscent of previous results in the literature found in the limit of weak coupling without magnetic field. The 2SC gap in the strong coupling regime is abruptly quenched at ultrahigh magnetic field due to the mismatched Fermi surfaces of up and down quarks imposed by charge neutrality and oscillation of the gap due to Landau level quantization. The dynamical quark mass also displays strong oscillation and magnetic catalysis at high magnetic field, although the latter effect is tempered by nonzero temperature. We discuss the implications for newly born compact stars with superconducting quark cores.
Robert Fleischer🇳🇱 · Ruben Jaarsma🇳🇱 · K. Keri Vos🇳🇱
The -spin symmetry provides a powerful tool to extract the angle of the Unitarity Triangle and the - mixing phase from CP violation in the , system. LHCb has obtained first results with uncertainties at the level. Due to -spin-breaking corrections, it will be challenging to reduce the uncertainty below at Belle II and the LHCb upgrade. We propose a new strategy, using as input and utilizing , decays, which allows an extraction of with a future theoretical precision of up to , thereby matching the experimental prospects. Since is dominated by penguin topologies, new sources of CP violation may be revealed.
In this work I present the interpretation of the ATLAS search of same-sign lepton production in association with -jets in the context of the 4-top quark signal from sgluon decays. I show that using just 3.2/fb data sample from Run 2 the exclusion limit is already competitive with the Run 1 one. Public data allow to exclude sgluons with masses up to 0.95 TeV. Prospects for the total Run 2 integrated luminosity of 100/fb are briefly discussed.
Andrew D. Bond🇬🇧 · Daniel F. Litim🇬🇧
We classify the weakly interacting fixed points of general gauge theories coupled to matter and explain how the competition between gauge and matter fluctuations gives rise to a rich spectrum of high- and low-energy fixed points. The pivotal role played by Yukawa couplings is emphasized. Necessary and sufficient conditions for asymptotic safety of gauge theories are also derived, in conjunction with strict no go theorems. Implications for phase diagrams of gauge theories and physics beyond the Standard Model are indicated.
The existence of the classical black hole solutions of the Einstein-Yang-Mills-Higgs equations with non-abelian Yang-Mills-Higgs hair, which we will also refer to as "magnetic monopole black hole solutions", implies that not all classical stationary magnetically charged black holes can be uniquely described by their asymptotic characteristics. In fact, in a certain domain of parameters, there exist different spherically-symmetric, non-rotating and asymptotically-flat classical black hole solutions of the EYMH equations which have the same ADM mass and the same magnetic charge but significantly different geometries in the near-horizon regions. (These are black hole solutions which are described by a Reissner-Nordström metric on the one hand and the hairy magnetic monopole black hole solutions which are described by a metric which is not of Reissner-Nordström form on the other hand.) One can experimentally distinguish such black holes with same asymptotic characteristics but different near-horizon geometries classically by probing the near-horizon regions of the black holes. We argue that one way to probe the near-horizon region of a black hole which allows to distinguish magnetically charged black holes with same asymptotic characteristics but different near-horizon geometries is by classical scattering of waves. Using the example of a minimally-coupled massless probe scalar field scattered by magnetically charged black holes which can be obtained as solutions of the EYMH equations with a Higgs triplett and gauge group SU(2) in the limit of an infinite Higgs self-coupling constant we show how, in this case, the scattering cross sections differ for the magnetically charged black holes with different near-horizon geometries but same asymptotic characteristics. We find in particular that the characteristic glory peaks in the cross sections are located at different scattering angles.
Sandeep Chatterjee🇮🇳 · Ajay Kumar Dash🇮🇳 · Bedangadas Mohanty🇮🇳
We study the data on mean hadron yields and contrast the chemical freezeout conditions in p+p, p+Pb and Pb+Pb at the Large Hadron Collider (LHC) energies. We study several schemes for freezeout that mainly differ in the way strangeness is treated: i. strangeness freezes out along with the non-strange hadrons in complete equilibrium (1CFO), ii. strangeness freezes out along with non-strange hadrons with an additional parameter accounting for non-equilibrium production of strangeness (1CFO+), and iii. strangeness freezes out earlier than non-strange hadrons and in thermal equilibrium (2CFO). A comparison of the chisquares of the fits indicate a dependence of the freezeout scheme on the system size. The minimum bias p+p and different centralities of p+Pb and peripheral Pb+Pb data prefer 1CFO with approaching unity as we go from p+p to central p+Pb and peripheral Pb+Pb. On the other hand, the mid-central to central Pb+Pb data prefer 2CFO over 1CFO+. Such system size dependence of freezeout scheme could be an indication of the additional interaction in Pb+Pb over p+Pb and p+p.
Sai Wang🇨🇳 · Yi-Fan Wang🇨🇳 · Dong-Mei Xia🇨🇳 · Xin Zhang🇨🇳
Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass by using recent cosmological observations. We consider two typical dark energy models, namely, the CDM model and the holographic dark energy (HDE) model, which both have an additional free parameter compared with the CDM model. We employ the Planck 2015 data of CMB temperature and polarization anisotropies, combined with low-redshift measurements on BAO distance scales, type Ia supernovae, Hubble constant, and Planck lensing. Compared to the CDM model, our study shows that the upper limit on becomes much looser in the CDM model while much tighter in the HDE model. In the HDE model, we obtain the CL upper limit for three degenerate neutrinos. This might be the most stringent constraint on by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal of the normal hierarchy is slightly smaller than that of the inverted hierarchy.
Valentin Lefranc🇫🇷 · Emmanuel Moulin🇫🇷 · Paolo Panci🇫🇷 · Filippo Sala🇫🇷 · Joseph Silk🇫🇷
We provide CTA sensitivities to Dark Matter (DM) annihilation in -ray lines, from the observation of the Galactic Center (GC) as well as, for the first time, of dwarf Spheroidal galaxies (dSphs). We compare the GC reach with that of dSphs as a function of a putative core radius of the DM distribution, which is itself poorly known. We find that the currently best dSph candidates constitute a more promising target than the GC, for core radii of one to a few kpc. We use the most recent instrument response functions and background estimations by CTA, on top of which we add the diffuse photon component. Our analysis is of particular interest for TeV-scale electroweak multiplets as DM candidates, such as the supersymmetric Wino and the Minimal Dark Matter fiveplet, whose predictions we compare with our projected sensitivities.
Johannes M. Henn🇩🇪 · Bernhard Mistlberger🇨🇭
We compute the three-loop four-gluon scattering amplitude in maximally supersymmetric Yang-Mills theory, including its full color dependence. Our result is the first complete computation of a non-planar four-particle scattering amplitude to three loops in four-dimensional gauge theory and consequently provides highly non-trivial data for the study of non-planar scattering amplitudes. We present the amplitude as a Laurent expansion in the dimensional regulator to finite order, with coefficients composed of harmonic poly-logarithms of uniform transcendental weight, and simple rational prefactors. Our computation provides an independent check of a recent result for three-loop corrections to the soft anomalous dimension matrix that predicts the general infrared singularity structure of massless gauge theory scattering amplitudes. Taking the Regge limit of our result, we determine the three-loop gluon Regge trajectory. We also find agreement with very recent predictions for sub-leading logarithms.
The ground-state hyperfine splitting of antihydrogen promises one of the most sensitive tests of CPT symmetry. The ASACUSA collaboration is pursuing a measurement of this splitting in a Rabi-type experiment using a polarized beam from a CUSP magnet at the Antiproton Decelerator of CERN. With the initial intention of characterizing the Rabi apparatus, a polarized source of cold hydrogen was built and the transition of hydrogen was measured to a few ppb precision. A measurement of the transition is being prepared. The availability of this beam opens the possibility to perform first measurements of some coefficients within the nonminimal Standard-Model Extension.
* 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.