HEP Phenomenology·hep-ph
30 papers—22 primary·8 cross-listed·reconstructed*
Neutrino physics is currently suffering from lack of knowledge from at least four major ingredients. One of them is the presence or not of new sterile neutrino states at the mass scale of around 1 eV. Settling this point should be the highest priority for the neutrino community. We will discuss the state-of-the art of experimental searches for sterile neutrinos with accelerators, both at long and short baselines.
V. M. Banda Guzman🇲🇽 · M. Kirchbach🇲🇽
The Bargmann-Wigner (BW) framework describes particles of spin-j in terms of Dirac spinors of rank 2j, obtained as the local direct product of n Dirac spinor copies, with n=2j. Such spinors are reducible, and contain also (j,0)+(0,j)-pure spin representation spaces. The 2(2j+1) degrees of freedom of the latter are identified by a projector given by the n-fold direct product of the covariant parity projector within the Dirac spinor space. Considering totally symmetric tensor spinors one is left with the expected number of 2(2j+1) independent degrees of freedom. The BW projector is of the order in the derivatives, and so are the related spin-j wave equations and associated Lagrangians. High order differential equations can not be consistently gauged, and allow several unphysical aspects, such as non-locality, acausality, ghosts and etc to enter the theory. In order to avoid these difficulties we here suggest a strategy of replacing the high order of the BW wave equations by the universal second order. To do so we replaced the BW projector by one of zeroth order in the derivatives. We built it up from one of the Casimir invariants of the Lorentz group when exclusively acting on spaces of internal spin degrees of freedom. This projector allows one to identify anyone of the irreducible sectors of the primordial rank-2j spinor, in particular (j,0)+(0,j), and without any reference to the external space-time and the four-momentum. The dynamics is then introduced by requiring the (j,0)+ (0,j) sector to satisfy the Klein-Gordon equation. The scheme allows for a consistent minimal gauging.
Ansgar Denner🇩🇪 · Stefan Dittmaier🇩🇪 · Lars Hofer🇪🇸
We present the library Collier for the numerical evaluation of one-loop scalar and tensor integrals in perturbative relativistic quantum field theories. The code provides numerical results for arbitrary tensor and scalar integrals for scattering processes in general quantum field theories. For tensor integrals either the coefficients in a covariant decomposition or the tensor components themselves are provided. Collier supports complex masses, which are needed in calculations involving unstable particles. Ultraviolet and infrared singularities are treated in dimensional regularization. For soft and collinear singularities mass regularization is available as an alternative.
Yonit Hochberg🇺🇸 · Tongyan Lin🇺🇸 · Kathryn M. Zurek🇺🇸
Superconducting targets have recently been proposed for the direct detection of dark matter as light as a keV, via elastic scattering off conduction electrons in Cooper pairs. Detecting such light dark matter requires sensitivity to energies as small as the superconducting gap of O(meV). Here we show that these same superconducting devices can detect much lighter DM, of meV to eV mass, via dark matter absorption on a conduction electron, followed by emission of an athermal phonon. We demonstrate the power of this setup for relic kinetically mixed hidden photons, pseudoscalars, and scalars, showing the reach can exceed current astrophysical and terrestrial constraints with only a moderate exposure.
I. Brivio🇪🇸 · J. Gonzalez-Fraile🇩🇪 · M. C. Gonzalez-Garcia🇪🇸 · L. Merlo🇪🇸
The complete effective chiral Lagrangian for a dynamical Higgs is presented and constrained by means of a global analysis including electroweak precision data together with Higgs and triple gauge boson coupling data from the LHC Run~I. The operators' basis up to next-to-leading order in the expansion consists of 148 (188 considering right-handed neutrinos) flavour universal terms and it is presented here making explicit the custodial nature of the operators. This effective Lagrangian provides the most general description of the physical Higgs couplings once the electroweak symmetry is assumed, and it allows for deviations from the doublet nature of the Standard Model Higgs. The comparison with the effective linear Lagrangian constructed with an exact doublet Higgs and considering operators with at most canonical dimension six is presented. A promising strategy to disentangle the two descriptions consists in analysing i) anomalous signals present only in the chiral Lagrangian and not expected in the linear one, that are potentially relevant for LHC searches, and ii) decorrelation effects between observables that are predicted to be correlated in the linear case and not in the chiral one. The global analysis presented here, that includes several kinematic distributions, is crucial for reducing the allowed parameter space and for controlling the correlations between parameters. This improves previous studies aimed at investigating the Higgs Nature and the origin of the electroweak symmetry breaking.
Marco Fabbrichesi🇮🇹 · Michele Pinamonti🇮🇹 · Alfredo Urbano🇨🇭
We argue that the spin of the 750 GeV resonance can be determined at the 99.7% confidence level in the di-photon channel with as few as 10 fb of luminosity. This result is true if the resonance is produced by gluon fusion (independently of the selection cuts) while an appropriate choice of selection cuts is needed if quark production is sub-dominantly present--which is the case of the Kaluza-Klein gravitational excitation under the hypothesis of a spin-2 resonance. A proportionally larger luminosity is required if the model for the spin-2 resonance includes a dominant production by quarks or in the absence of an efficient separation of the signal from the background.
J. Chakrabortty🇮🇳 · J. Gluza🇵🇱 · T. Jelinski🇵🇱 · T. Srivastava🇮🇳
Left-Right symmetric models with general gauge couplings which include bidoublet and triplet scalar multiplets are studied. Possible scalar mass spectra are outlined by imposing Tree-Unitarity, and Vacuum Stability criteria and also using the bounds on neutral scalar masses which assure the absence of Flavour Changing Neutral Currents (FCNC). We are focusing on mass spectra relevant for the LHC analysis, i.e., the scalar masses are around TeV scale. As all non-standard heavy particle masses are related to the vacuum expectation value (VEV) of the right-handed triplet (), the combined effects of relevant Higgs potential parameters and regulate the lower limits of heavy gauge boson masses. The complete set of Renormalization Group Evolutions for all couplings are provided at the 1-loop level, including the mixing effects in the Yukawa sector. Most of the scalar couplings suffer from the Landau poles at the intermediate scale GeV, which in general coincides with violation of the Tree-Unitarity bounds.
Goran Duplancic🇭🇷 · Bruno Klajn🇭🇷
We present a completely numerical method of calculating one-loop amplitudes. Our approach is built upon two different existing methods: the contour deformation and the extrapolation methods. Taking the best features of each of them, we devise an intuitive, stable and robust procedure which circumvents the problem of large cancellations and related numerical instabilities by calculating the complete amplitude at once. As a proof of concept, we use our method to calculate the benchmark process, as well as the Higgs decay amplitude .
Junfeng Sun🇨🇳 · Yueling Yang🇨🇳 · Qingxia Li🇨🇳 · Gongru Lu🇨🇳 · Jinshu Huang🇨🇳 · Qin Chang🇨🇳
The weak decay is studied with the perturbative QCD approach firstly. It is found that (1) main contributions to branching ratio come from the longitudinal and parallel helicity amplitudes, (2) branching ratio, longitudinal and parallel polarization fractions are sensitive to the wave functions of the meson, (3) branching ratio for the decay can reach up to , which might be promisingly measured by the future experiments.
Directly measuring the Higgs self-coupling is of great importance for testing the Brout-Englert-Higgs mechanism in the Standard Model. As a scattering that contains the direct information from the Higgs self-coupling, we investigate the process in the threshold region. We calculate the one-loop corrections to the cross section and consider the non-perturbative contribution from the Higgs self-interactions in the final state. It is found that the scattering in the nonrelativistic domain could be an especial process to testing the Higgs sector directly.
Kenneth Lane🇺🇸 · Lukas Pritchett🇺🇸
This paper extends an earlier one describing the Higgs boson as a light composite scalar in a strong extended technicolor model of electroweak symmetry breaking. The Higgs mass is made much smaller than by tuning the ETC coupling very close to the critical value for electroweak symmetry breaking. The technicolor interaction, neglected in the earlier paper, is considered here. Its weakness relative to extended technicolor is essential to understanding the lightness of compared to the low-lying spin-one technihadrons. Technicolor cannot be completely ignored, but implementing technigluon exchange together with strong extended technicolor appears difficult. We propose a solution that turns out to leave the results of the earlier paper essentially unchanged. An argument is then presented that masses of the spin-one technifermion bound states, and , are much larger than and, plausibly, controlled by technicolor. Assuming and are in the TeV-energy region, we identify and with the diboson excesses observed near by ATLAS and CMS in LHC Run 1 data, and we discuss their phenomenology for Runs 2 and 3.
Fuminobu Takahashi🇯🇵 · Masaki Yamada🇯🇵 · Norimi Yokozaki🇯🇵
We show that the 750 GeV diphoton excess can be explained by introducing vector-like quarks and hidden fermions charged under a hidden U(1) gauge symmetry, which has a relatively large coupling constant as well as a significant kinetic mixing with U(1). With the large kinetic mixing, the standard model gauge couplings unify around GeV, suggesting the grand unified theory without too rapid proton decay. Our scenario predicts events with a photon and missing transverse momentum, and its cross section is related to that for the diphoton excess through the kinetic mixing. We also discuss other possible collider signatures and cosmology, including various ways to evade constraints on exotic stable charged particles. In some cases where the 750 GeV diphoton excess is due to diaxion decays, our scenario also predicts triphoton and tetraphoton signals.
Tom Kaufmann🇩🇪 · Asmita Mukherjee🇮🇳 · Werner Vogelsang🇩🇪
We argue that the process , for which a photon is observed inside a fully reconstructed jet and is treated as part of the jet, offers new probes of the so far little known fragmentation functions for photons. We present a next-to-leading-order QCD calculation of the cross section for this process in the limit that the jet is relatively narrow. We also investigate the background resulting from the two-photon decay of neutral pions. We present numerical results relevant for possible measurements at the LHC and at RHIC. These suggest that should provide clean access to the photon fragmentation functions, provided an efficient suppression of the background is available in experiment.
Rather than attempting to summarise the full spectrum of recent advances in Beyond the Standard Model (BSM) theory, which are many, in this talk I will instead take the opportunity to focus on two frameworks related to the hierarchy problem currently receiving significant attention. They are the `Twin Higgs' and the `Relaxion'. I will summarise the basic underlying structure of these theories at a non-expert level and highlight some interesting phenomenological signatures or outstanding problems.
Masaki Yamada🇯🇵 · Tsutomu T. Yanagida🇯🇵 · Kazuya Yonekura🇯🇵
We provide a theory with a monopole of a strongly-interacting hidden U(1) gauge symmetry that can explain the 750-GeV diphoton excess reported by ATLAS and CMS. The excess results from the resonance of monopole, which is produced via gluon fusion and decays into two photons. In the low energy, there are only mesons and a monopole in our model because any baryons cannot be gauge invariant in terms of strongly interacting Abelian symmetry. This is advantageous of our model because there is no unwanted relics around the BBN epoch.
Shigehiro Yasui🇯🇵 · Kei Suzuki🇯🇵 · Kazunori Itakura🇯🇵
We discuss the ground state of a quark matter containing heavy quarks as impurities in a simple model which exhibits the QCD Kondo effect. The model includes a current-current interaction with the color exchange between a light quark () and a heavy quark (). We introduce a gap function which represents the correlation between and , and perform the mean-field approximation assuming that heavy quarks are uniformly distributed. Values of the gap measure the strength of mixing between and . The gap equation obtained from the minimum of the thermodynamical potential together with the condition for the heavy-quark number conservation turns out to allow for nonzero values of the gap as the most stable state. We draw a phase diagram in (the light-quark chemical potential) and (an analog of the heavy-quark chemical potential) plane, and identify the region where the QCD Kondo effect occurs.
Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸
Experimental results of the transverse momentum distributions of phi mesons and hyperons produced in gold-gold (Au-Au) collisions with different centrality intervals, measured by the STAR Collaboration at different energies (7.7, 11.5, 19.6, 27, and 39 GeV) in the beam energy scan (BES) program at the relativistic heavy ion collider (RHIC), are approximately described by the single Erlang distribution and the two-component Schwinger mechanism. Meanwhile, the STAR experimental transverse momentum distributions of negatively charged particles, produced in Au-Au collisions at RHIC BES energies, are approximately described by the two-component Erlang distribution and the single Tsallis statistics. The excitation functions of free parameters are obtained from the fit to the experimental data. A weak softest point in the string tension in hyperon spectra is observed at 7.7 GeV.
We present a preliminary study of both Single and Double Parton Scattering contributions to the inclusive 4-jet production in the kt-factorization framework at Leading Order and TeV. We compare our results to collinear results in the literature and to the ATLAS and CMS data at 8 and 7 TeV respectively. We also discuss the importance of double parton scattering for relatively soft cuts on the jet transverse momenta and find out that symmetric cuts do not quite suit well to kt-factorization predictions, because of a kinematic effect suppressing the double parton scattering contribution.
N. Matagne🇧🇪 · Fl. Stancu🇧🇪
The mass spectra of the and multiplets, both belonging to the = 2 band, is reviewed in the expansion method. Previous studies, separately made for each multiplet, are presently updated to the 2014 Particle Data Group. The mass formula including corrections up to and first order in SU(3) flavor symmetry breaking, has the same independent operator basis in both cases. A special emphasis is made on the role of the SU(3) symmetry breaking operators . This can allow for multiplet assignment of and hyperons, which generally is quite difficult to make. Tentative assignments of hyperons with two- and one-star resonances are made to the multiplet. Another important aim is to find out whether or not a common value of the coefficient of the dominant operator in the mass formula, can well fit the present data in both multiplets. A negative answer, which is here the case, implies distinct Regge trajectories for symmetric and mixed symmetric states.
R.B. Appleby🇬🇧 · R.J. Barlow🇬🇧 · J.G Molson🇫🇷 · M. Serluca🇨🇭 · A. Toader🇬🇧
We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation n high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer~,as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC.We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC.
Neutrinos play a key role in core-collapse supernova explosions. Carrying information from deep inside the stellar core, neutrinos are direct probes of the supernova mechanism. Intriguing recent developments on the role of neutrinos in supernovae are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope, and the detection perspectives of the next burst.
The lack of evidence for low energy supersymmetry at the LHC implies a supersymmetry scale in excess a TeV. While this is consistent (and even helpful) with a Higgs boson mass at 125 GeV, simple supersymmetric models with scalar and gaugino mass universality are being pushed into strips of parameter space. These often require coannihilations to obtain an acceptable relic density and the extent of these coannihilation strips will be discussed. In contrast, non-supersymmetric grand unified theories such as SO(10) may also provide a dark matter candidate. Because of the presence of an intermediate scale, these theories may unify gauge couplings, provide for neutrino masses and a suitably long lived proton.
Won-Gi Paeng · Mannque Rho
When a light scalar dilaton and the light-quark vector mesons are incorporated into an effective scale-invariant hidden local symmetric (sHLS) Lagrangian, scale symmetry for and local gauge symmetry for , both invisible in QCD in the vacuum, arise as emergent symmetries at a density above , a phenomenon highly relevant for massive compact stars, hitherto unobserved in standard chiral pertubative approaches. What takes place involves a topology change at , and as the density increases beyond, (1) exposes a parity doubling in the nucleon structure, (2) triggers drastic change in the nuclear tensor force and (3) stiffens the nuclear symmetry energy as density exceeds . It results from an intricate interplay between the two hidden symmetries that the meson moves toward the vector manifestation (VM) fixed point where and the velocity of sound in the dense matter approaches the conformal symmetry value , indicating a presence of an infrared fixed point at which the dilaton mass vanishes.
Janus Weil🇩🇪 · Jan Staudenmaier🇩🇪 · Hannah Petersen🇩🇪
In this work the SMASH model is presented ("Simulating Many Accelerated Strongly-Interacting Hadrons"), a next-generation hadronic transport approach, which is designed to describe the non-equilibrium evolution of hadronic matter in heavy-ion collisions. We discuss first dilepton spectra obtained with SMASH in the few-GeV energy range of GSI/FAIR, where the dynamics of hadronic matter is dominated by the production and decay of various resonance states. In particular we show how electromagnetic transition form factors can emerge in a transport picture under the hypothesis of vector-meson dominance.
Violation of the action-reaction principle is shown to occur in the van der Waals interaction between two atoms, one of which is excited. It is accompanied by the transfer of linear momentum to the electromagnetic vacuum. The vacuum momentum results from the asymmetric interference of the virtual photons scattered off each atom along the interatomic direction, which is in itself a manifestation of the optical theorem. This momentum, of equal strength and opposite direction to the momentum gained by the two-atom system, is ultimately released through directional spontaneous emission. A quantitative prediction of this phenomenon is made in a two-alkali atom system. It is conjectured that action-reaction violation takes place in any asymmetrically excited system.
Z. Fodor🇩🇪 · C. Hoelbling🇩🇪 · S. Krieg🇩🇪 · L. Lellouch🇫🇷 · Th. Lippert🇩🇪 · A. Portelli🇬🇧 · A. Sastre🇩🇪 · K.K. Szabo🇩🇪 · L. Varnhorst🇩🇪
In a previous letter (arXiv:1306.2287) we determined the isospin mass splittings of the baryon octet from a lattice calculation based on quenched QED and QCD simulations with 5 lattice spacings down to , lattice sizes up to and average up-down quark masses all the way down to their physical value. Using the same data we determine here the corrections to Dashen's theorem and the individual up and down quark masses. For the parameter which quantifies violations to Dashens's theorem, we obtain , where the first error is statistical, the second is systematic, and the third is an estimate of the QED quenching error. For the light quark masses we obtain, and in the scheme at and the isospin breaking ratios , and . Our results exclude the solution to the strong CP problem by more than standard deviations.
We construct the gravitational solution of the Witten-Sakai-Sugimoto model by introducing a magnetic field on the flavor brane. With taking into account their backreaction, we re-solve the type IIA supergravity in the presence of the magnetic field. Our calculation shows the gravitational solutions are magnetic-dependent and analytic both in the bubble (confined) and black brane (deconfined) case. We study the dual field theory at the leading order in the ratio of the number of flavors and colors, also in the Veneziano limit. Some physical properties related to the hadronic physics in an external magnetic field are discussed by using our confined backreaction solution holographically. We also investigate the thermodynamics and holographic renormalization of this model in both phases by our solution. Since the backreaction of the magnetic field is considered in our gravitational solution, it allows us to study the Hawking-Page transition with flavors and colors of this model in the presence of the magnetic field. Finally we therefore obtain the holographic phase diagram with the contributions from the flavors and the magnetic field. Our holographic phase diagram is in agreement with lattice QCD result qualitatively, which thus can be interpreted as the inhibition of confinement or chirally broken symmetry by the magnetic field.
Hanna Grönqvist🇫🇷 · Jean-Paul Blaizot🇫🇷 · Jean-Yves Ollitrault🇫🇷
We study the fluctuations of the anisotropy of the energy density profile created in a high-energy collision at the LHC. We show that the anisotropy in harmonic has generic non-Gaussian fluctuations. We argue that these non-Gaussianities have a universal character for small systems such as p+Pb collisions, but not for large systems such as Pb+Pb collisions where they depend on the underlying non-Gaussian statistics of the initial density profile. We generalize expressions for the eccentricity cumulants and previously obtained within the independent-source model to a general fluctuating initial density profile.
Jason S.-Y. Leung🇨🇦 · Zhiqi Huang🇨🇦
We use effective field theory (EFT) formalism to forecast the constraint on Horndeski class of dark energy models with future supernova and galaxy surveys. Previously (Gleyzes {\it et al.}) computed unmarginalized constraints (68\% CL error --) on EFT dark energy parameters by fixing all other parameters. We extend the previous work by allowing all cosmological parameters and nuisance parameters to vary and marginalizing over them. We find that (i) the constraints on EFT dark energy parameters are typically worsen by a factor of few after marginalization, and (ii) the constraint on the dark energy equation of state is not significantly affected by the inclusion of EFT dark energy parameters.
Yoichiro Nambu put a great foot print in nuclear physics in the era of its fundamental developments including his pioneering insight into essential ingredients of repulsive core of nuclear force and its relation to the saturation of nuclear matter. The present review article focuses onto recent developments of the interaction models between colliding nuclei in terms of Brueckner's G-matrix theory staring from realistic nuclear forces and the saturation property of symmetric nuclear matter as well as neutron-star matter. A recently proposed unique scenario of extracting the saturation property of nuclear matter and stiffness of neutron stars through the analysis of nucleus-nucleus elastic scattering in laboratories is presented in some detail.
* 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.