HEP Phenomenology·hep-ph
29 papers—24 primary·5 cross-listed·reconstructed*
We review the next generation global PDF sets: NNPDF3.0, MMHT14 and CT14. We describe the global datasets, particularly the new data from LHC Run 1, recent developments in QCD theory and PDF methodology, improvements in combination and delivery, and future prospects for parton determination at Run 2.
Doojin Kim🇺🇸 · Jong-Chul Park🇰🇷
We propose a novel mechanism enabling us to have a continuum bump as a signature of gamma-ray excess in indirect detection experiments of dark matter (DM), postulating a generic dark sector having (at least) two DM candidates. With the assumption of non-zero mass gap between the two DM candidates, the heavier one directly communicates to the partner of the lighter one. Such a partner then decays into a lighter DM particle along with an "axion-like" particle (ALP) or dark "pion", which subsequently decays into a pair of photons, via a more-than-one step cascade decay process. Since the cascade is initiated by the dark partner obtaining a non-trivial fixed boost factor, a continuum gamma-ray energy spectrum naturally arises even with a particle directly decaying into two photons. We apply the main idea to the energy spectrum of the GeV gamma-rays from around the Galactic Center (GC), and find that the relevant observational data is well-reproduced by the theory expectation predicted by the proposed mechanism. Remarkably, the relevant energy spectrum has a robust peak at half the mass of the ALP or dark pion, as opposed to popular DM models directly annihilating to Standard Model particles where physical interpretations of the energy peak are not manifest. Our data analysis reports substantially improved fits, compared to those annihilating DM models, and ~900 MeV mass of the ALP or dark pion.
Matthew R. Buckley🇺🇸 · Dorival Goncalves🇬🇧
Characterizing the 125 GeV Higgs is a critical component of the physics program at the LHC Run II. In this Letter, we consider associated production in the dileptonic mode. We demonstrate that the difference in azimuthal angle between the leptons from top decays can directly reveal the CP-structure of the top-Higgs coupling with the sensitivity of the measurement substantiality enhanced in the boosted Higgs regime. We first show how to access this channel via jet-substructure tagging, then demonstrate the ability of the new variable to measure CP. Our analysis includes all signal and background samples simulated via the MC@NLO algorithm including hadronization and underlying-event effects. Using boosted Higgs substructure with dileptonic tops, we find that the top-Higgs coupling strength and the CP structure can be directly probed with achievable luminosity at the 13 TeV LHC.
Wolfgang Altmannshofer🇨🇦 · Stefania Gori🇨🇦 · Alexander L. Kagan🇺🇸 · Luca Silvestrini🇮🇹 · Jure Zupan🇺🇸
A discovery of the flavor violating decay h --> tau mu at the LHC would require extra sources of electroweak symmetry breaking (EWSB) beyond the Higgs in order to reconcile it with the bounds from tau --> mu gamma, barring fine-tuned cancellations. In fact, an h --> tau mu decay rate at a level indicated by the CMS measurement is easily realized if the muon and electron masses are due to a new source of EWSB, while the tau mass is due to the Higgs. We illustrate this with two examples: a two Higgs doublet model, and a model in which the Higgs is partially composite, with EWSB triggered by a technicolor sector. The 1st and 2nd generation quark masses and CKM mixing can also be assigned to the new EWSB source. Large deviations in the flavor diagonal lepton and quark Higgs Yukawa couplings are generic. If the muon mass is due to a rank 1 mass matrix contribution, a novel Yukawa coupling sum rule holds, providing a precision test of our framework. Flavor violating quark and lepton (pseudo)scalar couplings combine to yield a sizable B_s --> tau mu decay rate, which could be O(100) times larger than the SM B_s --> mu mu decay rate.
Daniel R. Bolton🇺🇸 · Raul A. Briceno🇺🇸 · David J. Wilson🇺🇸
We present a determination of the isovector, -wave scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using MeV. The finite volume spectra are described using extensions of Lüscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at MeV. The scattering phase shift is found to be in good agreement with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a -resonance pole at . The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.
M. Nebot🇵🇹 · Joao P. Silva🇵🇹
Flavour changing neutral scalar interactions are a standard feature of generic multi Higgs models. These are constrained by mixing in the neutral meson systems. We consider situations where there are natural cancellations in such contributions. In particular, when the spin 0 particle has both scalar and pseudoscalar couplings, one may have a self-cancellation. We illustrate one such partial cancellation with BGL models. We also inquire whether the flavour changing quark interactions can lead to new production mechanisms for a neutral scalar at LHC.
Bo Wang🇨🇳 · Hao Xu🇨🇳 · Xiang Liu🇨🇳 · Dian-Yong Chen🇨🇳 · Susana Coito🇨🇳 · Estia Eichten🇺🇸
Very recently, the Belle and BESIII experiments observed a new charmonium-like state , which is a good candidate for the -wave charmonium . Because the is just near the threshold, the decay can be a golden channel to test the significance of coupled-channel effects. In this work, this decay is considered including both the hidden-charm dipion and the usual quantum chromodynamics multipole expansion (QCDME) contributions. The partial decay width, the dipion invariant mass spectrum distribution , and the corresponding distribution are computed. Many parameters are determined from existing experimental data, so the results depend mainly only on one unknown phase between the QCDME and hidden-charm dipion amplitudes.
G. Belanger🇫🇷 · J. Da Silva🇬🇧 · T. Perrillat-Bottonet🇫🇷 · A. Pukhov🇷🇺
Limits on dark matter spin dependent elastic scattering cross section on protons derived from IceCube data are obtained for different dark matter annihilation channels using micrOMEGAs. The uncertainty on the derived limits, estimated by using different neutrino spectra, can reach a factor two. For all dark matter annihilation channels except for quarks, the limits on the spin dependent cross section are more stringent than those obtained in direct detection experiments. The new functions that allow to derive those limits are described.
Min He🇨🇳 · Xiao-Gang He🇨🇳 · Guan-Nan Li🇹🇼
Several baryons containing a heavy b-quark, the b-baryons, have been discovered. The charmless two-body decays of b-baryons can provide a new platform for CP violating studies in a similar way as charmless two-body decays of B-meson. In b-baryon decays there are new CP violating observable related to baryon polarization. We show that in the flavor limit there exist relations involve different combinations of the decay amplitudes compared with those in CP violating rate asymmetry. These new relations therefore provide interesting tests for the mechanism of CP in the standard model (SM) and flavor symmetry. Future data from LHCb can test these relations.
We discuss the Top Mode pseudo Nambu-Goldstone boson Higgs (TMpNGBH) model which has recently been proposed as a variant of the top quark condensate model in light of the 125 GeV Higgs boson discovered at the LHC. In this talk, we focus on the vacuum alignment and the phenomenologies of characteristic particles of the TMpNGBH model.
J. Vijande🇪🇸 · A. Valcarce🇪🇸
We present a plausible mechanism for the origin of the mesons in the heavy meson spectra within a standard quark-model picture. We discuss the conditions required for the existence of four--quark bound states or resonances contributing to the heavy meson spectra, being either compact or molecular. We concentrate on charmonium and bottomonium spectra, where several new states, difficult to understand as simple quark-antiquark pairs, have been reported by different experimental collaborations. The pivotal role played by entangled meson-meson thresholds is emphasized.
T.F. Carames🇪🇸 · A. Valcarce🇪🇸
We study possible multiquark contributions to the charm baryon spectrum by considering higher order Fock space components. For this purpose we perform two different calculations. In a first approach we do a coupled-channel calculation of the system looking for molecular states. In a second step we allow for the coupling to a heavy baryon--light meson two-hadron system looking for compact exotic five--quark structures. Both calculations have been done within the framework of a chiral constituent quark model. The model, tuned in the description of the baryon and meson spectra as well as the interaction, provides parameter-free predictions for charm molecular or compact two-hadron systems. Unlike the system, no sharp quark-Pauli effects are found. However, the existence of different two-hadron thresholds for the five-quark system will make the coupled-channel dynamics relevant. Only a few channels are candidates to lodge molecular or compact hadrons with a five-quark structure, being specially relevant the and channels. The identification of molecular states and/or compact hadrons with multiquark components either with or without exotic quantum numbers is a challenge of different collaborations like ANDA, LHCb, ExHIC or J-PARC.
Eung Jin Chun🇰🇷 · Zhaofeng Kang🇰🇷 · Michihisa Takeuchi🇯🇵 · Yue-Lin Sming Tsai🇯🇵
The lepton-sepcific (or type X) 2HDM (L2HDM) is an attractive new physics candidate explaining the muon anomaly requiring a light CP-odd boson and large . This scenario leads to -rich signatures, such as , and , which can be readily accessible at the LHC. We first study the whole L2HDM parameter space to identify allowed regions of extra Higgs boson masses as well as two couplings and which determine the 125 GeV Higgs boson decays and , respectively. This motivates us to set up two regions of interest: (A) , and (B) , for which derive the current constraints by adopting the chargino-neutralino search at the LHC8, and then analyze the LHC14 prospects by implementing -tagging algorithm. A correlated study of the upcoming precision determination of the 125 GeV Higgs boson decay properties as well as the observation of multi-tau events at the next runs of LHC will be able to shed light on the L2HDM option for the muon .
Guillermo Garcia Fernandez🇪🇸 · Jesus Guerrero Rojas🇪🇸 · Felipe J. Llanes-Estrada (U. Complutense Madrid)🇪🇸
The gauge symmetry of the Standard Model is SU(3)_c x SU(2)_L x U(1)_Y for unknown reasons. One aspect that can be addressed is the low dimensionality of all its subgroups. Why not much larger groups like SU(7), or for that matter, SP(38) or E7? We observe that fermions charged under large groups acquire much bigger dynamical masses, all things being equal at a high e.g. GUT scale, than ordinary quarks. Should such multicharged fermions exist, they are too heavy to be observed today and have either decayed early on (if they couple to the rest of the Standard Model) or become reliquial dark matter (if they don't). The result follows from strong antiscreening of the running coupling for those larger groups (with an appropriately small number of flavors) together with scaling properties of the Dyson-Schwinger equation for the fermion mass.
Ali H. Chamseddine🇱🇧 · Alain Connes🇫🇷 · Walter D. van Suijlekom🇳🇱
We analyze the running at one-loop of the gauge couplings in the spectral Pati-Salam model that was derived in the framework of noncommutative geometry. There are a few different scenario's for the scalar particle content which are determined by the precise form of the Dirac operator for the finite noncommutative space. We consider these different scenarios and establish for all of them unification of the Pati-Salam gauge couplings. The boundary conditions are set by the usual RG flow for the Standard Model couplings at an intermediate mass scale at which the Pati-Salam symmetry is broken.
Fa Peng Huang🇨🇳 · Chong Sheng Li🇨🇳
We study the electroweak baryogenesis in the framework of the effective field theory. Our study shows that by introducing a light singlet scalar particle and a dimension-5 operator, it can provide the strong first order phase transition and the source of the CP-violation during the phase transition, and then produce abundant particle phenomenology at zero temperature. We also show the constraints on the new physics scale from the observed baryon-to-photon ratio, the low-energy experiments, and the LHC data.
Michelangelo L. Mangano🇨🇭 · Tilman Plehn🇩🇪 · Peter Reimitz🇩🇪 · Torben Schell🇩🇪 · Hua-Sheng Shao🇨🇭
We propose a measurement of the top Yukawa coupling at a 100 TeV hadron collider, based on boosted Higgs and top decays. We find that the top Yukawa coupling can be measured to 1%, with excellent handles for reducing systematic and theoretical uncertainties, both from side bands and from ratios.
Michal Praszalowicz🇵🇱 · Anna Francuz🇵🇱
Analyzing recent ALICE data on inelastic pp scattering at the LHC energies we show that charged particle distributions exhibit geometrical scaling (GS). We show also that the inelastic cross-section is scaling as well and that in this case the quality of GS is better than for multiplicities. Moreover, exponent characterizing the saturation scale is for the cross-section scaling compatible with the one found in deep inelastic ep scattering at HERA. Next, by parametrizing charged particles distributions by the Tsallis-like formula, we find a somewhat unexpected solution that still exhibits GS, but differs from the "standard" one where the Tsallis temperature is proportional to the saturation scale.
Zhan Sun🇨🇳 · Xing-Gang Wu🇨🇳 · Hong-Fei Zhang🇨🇳
We present a systematical study on the prompt production in association with a pair via the process, , within the framework of non-relativistic QCD at the future high-energy collider - International Linear Collider (ILC), including both direct and feed-down contributions. For direct production, the states with color-octet channels, especially the and ones, provide dominant contribution to the production cross-section, which are about fifty-two times over that of the color-singlet one. This is clearly shown by the transverse momentum () and rapidity distributions. The feed-down contribution from and () is sizable, which is about to the total prompt cross-section. Besides the yields, we also calculate the polarization parameter . In small region, the polarization of the prompt is longitudinal due to large contributions through the channel, and becomes transverse in high region due to channel. Thus the production via photon-photon collisions at the ILC shall provide a useful platform for testing the color-octet mechanism.
S. Gariazzo🇮🇹 · C. Giunti🇮🇹 · M. Laveder🇮🇹 · Y.F. Li🇨🇳 · E.M. Zavanin🇧🇷
The theory and phenomenology of light sterile neutrinos at the eV mass scale is reviewed. The reactor, Gallium and LSND anomalies are briefly described and interpreted as indications of the existence of short-baseline oscillations which require the existence of light sterile neutrinos. The global fits of short-baseline oscillation data in 3+1 and 3+2 schemes are discussed, together with the implications for beta-decay and neutrinoless double-beta decay. The cosmological effects of light sterile neutrinos are briefly reviewed and the implications of existing cosmological data are discussed. The review concludes with a summary of future perspectives.
According to the long-standing received wisdom, a "small" value of the Higgs mass - as for instance implied by general unitarity constraints - is highly "unnatural" and essentially new physics to be present at or near currently accessible energy scales. Following the discovery of a new, Higgslike boson at the LHC facility in 2012, but with no sign of new physics after having explored a large region of parameter space, a dilemma thus seems to present itself : either the newly discovered boson is indeed the long-sought Higgs boson of the standard model of particle physics (or some appropriate variant of that model) and the new physics at the TeV scale, supposedly required by the naturalness argument, is still waiting to be discovered, possibly by LHC-II, or the identification of the new boson as the Higgs cannot be maintained. It is shown that this apparent dilemma is in fact a false one, in that nothing in contemporary particle physics dictates that a small Higgs mass be unnatural in any way.
We study the regularization dependence on the quenched Schwinger-Dyson equations in general gauge by applying the two types of regularizations, the four and three dimensional momentum cutoffs. The obtained results indicate that the solutions are not drastically affected by the choice of two different cutoff prescriptions. We then think that both the regularizations can nicely be adopted in the analyses for the Schwinger-Dyson equations.
T.F. Carames🇪🇸 · A. Valcarce🇪🇸
We study the two-baryon system with two units of charm looking for the possible existence of a loosely bound state resembling the dibaryon. We make use of a chiral constituent quark model tuned in the description of the baryon and meson spectra as well as the interaction. The presence of the heavy quarks makes the interaction simpler than in light baryon systems. We analyze possible quark-Pauli effects that would be present in spin-isospin saturated channels. Our results point to the non-existence of a charmed -like dibaryon, although it may appear as a resonance above the threshold.
Reggeon unitarity and non-abelian gauge field copies are focussed on as two Gribov discoveries that, it is suggested, may ultimately be seen as the most significant and that could, in the far distant future, form the cornerstones of his legacy. The crucial role played by the Gribov ambiguity in the construction of gauge theory bound-state amplitudes via reggeon unitarity is described. It is suggested that the existence of a physical, unitary, S-Matrix in a gauge theory is a major requirement that could even determine the theory.
Ezequiel Koile🇦🇷 · Nicolas Kovensky🇦🇷 · Martin Schvellinger🇦🇷
Differential cross sections of deep inelastic scattering of charged leptons from hadrons are investigated by using the gauge/string duality. We consider vector mesons derived from different holographic dual models obtaining a general expression. We focus on the strongly coupled regime of dual gauge theories for different values of the Bjorken parameter. We find new predictions which are particularly interesting for differential scattering cross sections of polarized leptons scattered off polarized vector mesons. We also carry out a detailed comparison of the moments of the structure functions with lattice QCD results.
H. Garcilazo🇲🇽 · A. Valcarce🇪🇸
It has been recently suggested the existence of a neutral bound state of two neutrons and a hyperon, . We point out that using either simple separable potentials or a full-fledged calculation with realistic baryon-baryon interactions derived from the constituent quark cluster model there is no possibility for the existence of such a bound state. For this purpose, we performed a full Faddeev calculation of the system in the channel using the interactions derived from the constituent quark cluster model which describe well the two-body and data and the hypertriton.
Rutger H. Boels🇩🇪 · Wadim Wormsbecher🇩🇪
Conformal invariance is spontaneously broken in many physical systems leading to the appearance of a single massless Goldstone mode in the spectrum, the dilaton. The dilaton soft limit is shown to generically encode the action of both the dilatation and the special conformal transformation on observables. For massive on-shell legs these take the form of sub-leading soft theorems. At loop level, we show how anomalous dimensions for coupling constants and fields can be included. We illustrate the general analysis with a variety of formal and phenomenological applications.
Laura Tolos🇩🇪 · Juergen Schaffner-Bielich🇩🇪 · Yannick Dengler
We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron star matter and white dwarf material. We consider non-self annihilating dark matter with an equation-of-state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses or lower and radii about one meter for weakly interacting dark matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses or lower and radii of a kilometer. These objects could be formed primordially and accrete white dwarf material subsequently. They could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed 2 pulsars set limits on the amount of dark matter inside neutron stars which is, at most, .
When averages of different experimental determinations of the same quantity are computed, each with statistical and systematic error components, then frequently the statistical and systematic components of the combined error are quoted explicitly. These are important pieces of information since statistical errors scale differently and often more favorably with the sample size than most systematical or theoretical errors. In this communication we describe a transparent procedure by which the statistical and systematic error components of the combination uncertainty can be obtained. We develop a general method and derive a general formula for the case of Gaussian errors with or without correlations. The method can easily be applied to other error distributions, as well. For the case of two measurements, we also define disparity and misalignment angles, and discuss their relation to the combination weight factors.
* 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.