HEP Phenomenology·hep-ph
19 papers—14 primary·5 cross-listed·reconstructed*
Lecture notes from the 2017 Les Houches Summer School on Effective Field Theories. The lectures covered introductory material on EFTs as used in high energy physics to compute experimentally observable quantities. Other lectures at the school covered a wide range of applications in greater depth.
Dorival Goncalves🇺🇸 · Kyoungchul Kong🇺🇸 · Jeong Han Kim🇺🇸
Constraining the Higgs boson properties is a cornerstone of the LHC program. We study the potential to directly probe the Higgs-top CP-structure via the channel at the LHC with the Higgs boson decaying to a bottom pair and top-quarks in the dileptonic mode. We show that a combination of laboratory and rest frame observables display large CP-sensitivity, exploring the spin correlations in the top decays. To efficiently reconstruct our final state, we present a method based on simple mass minimization and prove its robustness to shower, hadronization and detector effects. In addition, the mass reconstruction works as an extra relevant handle for background suppression. Based on our results, we demonstrate that the Higgs-top CP-phase can be probed up to at the high luminosity LHC.
Radiation spectra from ultra-relativistic electrons in thin [] and thick [] targets are discussed. The method of simplified averaging is described by examples of Landau-Pomeranchuk-Migdal effect and radiation at doughnut scattering. General infrared and ultraviolet asymptotic properties of radiation spectra are discussed.
Yuki Adachi🇯🇵 · Nobuhito Maru🇯🇵
We propose a new model of 5D gauge-Higgs unification with a successful electroweak symmetry breaking and a realistic Higgs boson mass. In our model, the representations of the fermions are very simple, the and representations of gauge group. Employing the anti-periodic boundary conditions for reduces massless exotic fermions and simplifies the brane localized mass terms. We calculate the 1-loop Higgs potential in detail and find that a realistic electroweak symmetry breaking and the observed Higgs mass are obtained.
Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷
The Kaon direct CP violation below the experimental data of a in the standard model, which is calculated using the RBC-UKQCD lattice and a large dual QCD, indicates the necessity of a new physics effect. In order to resolve the insufficient , we study the charged-Higgs contributions in a generic two-Higgs-doublet model. If we assume that the origin of the CP-violation phase is uniquely from the Kobayashi-Maskawa (KM) phase when the constraints from the - and -meson mixings, , and Kaon indirect CP violating parameter are simultaneously taken into account, it is found that the Kaon direct CP violation through the charged-Higgs effects can reach . Moreover, with the constrained values of the parameters, the branching ratios of the rare decays can be and , where the results can be tested through the NA62 experiment at CERN and the KOTO experiment at J-PARC, respectively.
A new QCD calculation of the B parameter of mixing is presented. It makes use of polynomial kernels in dispersion integrals in order to practically eliminate the contributions of the unknown pseudoscalar strange continuum. This approach avoids the arbitrariness and instability inherent to the Borel exponential kernels used in previous sum rules calculations. A simultaneous calculation of the mixed quark gluon condensate which enters in the expression for B is presented. Finally the K-meson decay constant is calculated to five loop
B. Ananthanarayan🇮🇳 · Johan Bijnens🇸🇪 · Samuel Friot🇫🇷 · Shayan Ghosh🇮🇳
In this work, we consider expressions for the masses and decay constants of the pseudoscalar mesons in chiral perturbation theory. These involve sunset diagrams and their derivatives evaluated at (). Recalling that there are three mass scales in this theory, , and , there are instances when the finite part of the sunset diagrams do not admit an expression in terms of elementary functions, and have therefore been evaluated numerically in the past. In a recent publication, an expansion in the external momentum was performed to obtain approximate analytic expressions for and , the pion mass and decay constant. We provide fully analytic exact expressions for and , the kaon and eta masses, and and , the kaon and eta decay constants. These expressions, calculated using Mellin-Barnes methods, are in the form of double series in terms of two mass ratios. A numerical analysis of the results to evaluate the relative size of contributions coming from loops, chiral logarithms as well as phenomenological low-energy constants is presented. We also present a set of approximate analytic expressions for , , and that facilitate comparisons with lattice results. Finally, we show how exact analytic expressions for and may be obtained, the latter having been used in conjunction with the results for to produce a recently published analytic representation of .
Kingman Cheung🇹🇼 · Wai-Yee Keung🇺🇸 · Po-Yan Tseng🇯🇵
We show that a novel decay mode of the bound state of stop-anti-stop pair in the ground state may have a significant branching ratio if the violating mixing appears in the stop sector, even after we apply the stringent constraint from the measurement of the electric dipole moment (EDM) of the electron. We show that the branching ratio can be as large as 10% in some parameter space that it may be detectable at the LHC.
Sheng-Quan Wang🇨🇳 · Xing-Gang Wu🇨🇳 · Wen-Long Sang🇨🇳 · Stanley J. Brodsky🇺🇸
The next-to-next-to-leading order (NNLO) pQCD prediction for the form factor was evaluated in 2015 using nonrelativistic QCD (NRQCD). A strong discrepancy between the NRQCD prediction and the BaBar measurements was observed. Until now there has been no solution for this puzzle. In this paper, we present a NNLO analysis by applying the Principle of Maximum Conformality (PMC) to set the renormalization scale. By carefully dealing with the light-by-light diagrams at the NNLO level, the resulting high precision PMC prediction agrees with the BaBar measurements within errors, and the conventional renormalization scale uncertainty is eliminated. The PMC is consistent with all of the requirements of the renormalization group, including scheme-independence. The application of the PMC thus provides a rigorous solution for the form factor puzzle, emphasizing the importance of correct renormalization scale-setting. The results also support the applicability of NRQCD to hard exclusive processes involving charmonium.
Marco Claudio Traini🇮🇹 · Jean-Paul Blaizot🇫🇷
Fluctuations play an important role in diffractive production of vector mesons. It was in particular recently suggested, based on the Impact-Parameter dependent Saturation model (IPSat), that geometrical fluctuations triggered by the motion of the constituent quarks within the protons could explain incoherent diffractive processes observed at HERA. We propose a variant of the IPSat model which includes spatial and symmetry correlations between constituent quarks, thereby reducing the number of parameters needed to describe diffractive vector meson production to a single one, the size of the gluon cloud around each valence quark. The application to , and diffractive electron and photon production cross sections reveal the important role of geometrical fluctuations in incoherent channels, while other sources of fluctuations are needed to fully account for electroproduction of light mesons, as well as photo production of mesons at small momentum transfer.
R. Baier🇩🇪 · A. Rebhan🇦🇹 · M. Wödlinger🇦🇹
The low-energy light-by-light cross section as determined by the nonlinear Euler-Heisenberg QED Lagrangian is evaluated in the presence of constant magnetic fields in the center-of-mass system of the colliding photons. This cross section has a complicated dependence on directions and polarizations. The overall magnitude decreases as the magnetic field is increased from zero, but this trend is reversed for ultrastrong magnetic fields , where the cross section eventually grows quadratically with the magnetic field strength perpendicular to the collision axis. This effect is due to interactions involving the lowest Landau level of virtual Dirac particles; it is absent in scalar QED. An even more dramatic effect is found for virtual charged vector mesons where the one-loop cross section diverges at the critical field strength due to an instability of the lowest Landau level and the possibility of the formation of a superconducting vacuum state. We also discuss (the absence of) implications for the recent observation of light-by-light scattering in heavy-ion collisions.
Zhi-Gang Wang🇨🇳 · Jun-Xia Zhang🇨🇳
In this article, we study the axialvector-diquark-scalar-diquark-antiquark type charmed pentaquark states with with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension in a consistent way. In calculations, we separate the contributions of the negative parity and positive parity pentaquark states unambiguously, and choose three sets input parameters to study the masses and pole residues of the charmed pentaquark states and in details. Then we estimate the masses of the charmed pentaquark states , , and with to be according to the breaking effects, which is compatible with the , , , .
Ram Brustein🇮🇱 · Yael Raveh🇮🇱
We investigate the possible detection of the Hypercharge Axion (HCA) in colliders. The HCA is a hypothetical pseudoscalar that couples to weak hypercharge topological density and could potentially explain the dominance of matter over antimatter in the observable universe. If the HCA exists, it can be produced in colliders via vector boson fusion or in association with a photon or with a Z boson, and detected by looking for its decay into photons or Z bosons. We find that for certain values of the HCA mass and coupling scales, both of the order of a TeV, existing data from the Large Hadron Collider (LHC) can already put interesting constraints and in future colliders, such as the High Luminosity LHC, the accessible detection range is increased significantly.
Hai Tao Li🇺🇸 · Jian Wang🇩🇪
We calculate the -jettiness soft function for production up to next-to-next-to-leading order in QCD, which is an important ingredient of the -jettiness subtraction method for predicting the differential cross sections of massive coloured particle productions. The divergent parts of the results have been checked using the renormalization group equations controlled by the soft anomalous dimension.
Heling Deng🇺🇸 · Mark P. Hertzberg🇺🇸 · Mohammad Hossein Namjoo🇺🇸 · Ali Masoumi🇺🇸
Recently there has been much interest in light dark matter, especially ultra-light axions, as they may provide a solution to the core-cusp problem at the center of galaxies. Since very light bosons can have a de Broglie wavelength that is of astrophysical size, they can smooth out the centers of galaxies to produce a core, as opposed to vanilla dark matter models, and so it has been suggested that this solves the core-cusp problem. In this work, we critically examine this claim. While an ultra-light particle will indeed lead to a core, we examine whether the relationship between the density of the core and its radius matches the data over a range of galaxies. We first review data that shows the core density of a galaxy varies as a function of the core radius as with . We then compare this to theoretical models. We examine a large class of light scalar dark matter models, governed by some potential . For simplicity, we take the scalar to be complex with a global symmetry in order to readily organize solutions by a conserved particle number. However, we expect our central conclusions to persist even for a real scalar, and furthermore, a complex scalar matches the behavior of a real scalar in the non-relativistic limit, which is the standard regime of interest. For any potential , we find the relationship between and for ground state solutions is always in one of the following regimes: (i) , or (ii) , or (iii) unstable, and so it never matches the data. We also find similar conclusions for virialized dark matter, more general scalar field theories, degenerate fermion dark matter, superfluid dark matter, and general polytropes. We conclude that the solution to the core-cusp problem is more likely due to either complicated baryonic effects or some other type of dark matter interactions.
Kazuhiro Kogai🇯🇵 · Takahiko Matsubara🇯🇵 · Atsushi J. Nishizawa🇯🇵 · Yuko Urakawa🇯🇵
In this paper, we explore a detectable imprint of massive fields with integer spins , which may be predicted from string theory. It was shown that such a massive non-zero spin field can generate the squeezed primordial bispectrum which depends on the angle between the two wavenumbers. We show that considering the contribution from the massive spin-2 field, the angular dependent primordial non-Gaussianity (PNG) yields a strong scale dependence in the bias parameter for the galaxy alignment, which becomes prominent at small scales. As another example of an angular dependent PNG, we also consider the primordial bispectrum where the angular dependence was introduced by a vector field, while breaking the global rotational symmetry. As a consequence, we find that the B-mode cosmic shear and non-diagonal components do not vanish. These aspects provide qualitative differences from the PNG sourced by massive non-zero spin fields.
Vladimir M. Braun🇩🇪 · Yao Ji🇩🇪 · Alexander N. Manashov🇩🇪
It was found that renormalization group equations in the heavy-quark effective theory (HQET) for the operators involving one effective heavy quark and light degrees of freedom are completely integrable in some cases and are related to spin chain models with the Hamiltonian commuting with the nondiagonal entry of the monodromy matrix. In this work we provide a more complete mathematical treatment of such spin chains in the QISM framework. We also discuss the relation of integrable models that appear in the HQET context with the large-spin limit of integrable models in QCD with light quarks. We find that the conserved charges and the "ground state" wave functions in HQET models can be obtained from the light-quark counterparts in a certain scaling limit.
Nikos Irges🇬🇷 · Fotis Koutroulis🇬🇷
We initiate the continuum description of a non-perturbative 5d lattice Yang-Mills model with 4d boundaries using the -expansion. In its simplest version classically the bulk has an gauge symmetry and on the boundary there is an Abelian-Higgs system with zero scalar potential. In part I we compute the Renormalization Group flows and related quantities in a limit where the boundary decouples from the bulk.
Chris Kouvaris🇩🇰 · Peter Tinyakov🇧🇪 · Michel H.G. Tytgat🇧🇪
We propose a mechanism that can convert a sizeable fraction of neutron stars into black holes with mass , too light to be produced via standard stellar evolution. We show that asymmetric fermionic dark matter of mass TeV, with attractive self-interaction within the range that alleviates the problems of collisionless cold dark matter, can accumulate in a neutron star and collapse, forming a seed black hole that converts the rest of the star to a solar mass black hole. We estimate the fraction of neutron stars that can become black holes without contradicting existing neutron star observations. Like neutron stars, such solar mass black holes could be in binary systems, which may be searched for by existing and forthcoming gravitational wave detectors. The (non-)observation of binary mergers of solar mass black holes may thus test the specific nature of the dark matter.
* 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.