HEP Phenomenology·hep-ph
11 papers—10 primary·1 cross-listed·reconstructed*
I review the physics case for flavour violating axions. In particular, I argue that relaxing the assumption of the universality of the Peccei-Quinn current opens up new pathways, including: the relaxation of the Supernova bound on the axion mass, a possible connection with the Standard Model flavour puzzle and the experimental opportunity of discovering the axion via flavoured axion searches.
Ruben Oncala🇫🇷 · Kalliopi Petraki🇫🇷
The formation of stable or meta-stable bound states can dramatically affect the phenomenology of dark matter (DM). Although the capture into bound states via emission of a vector is known to be significant, the capture via scalar emission suffers from cancellations that render it important only within narrow parameter space. While this is true for neutral scalar mediators, here we show that bound-state formation via emission of a charged scalar can be extremely significant. To this end, we consider DM charged under a dark force and coupled also to a light complex scalar that is charged under the same gauge symmetry. We compute the cross-sections for bound-state formation via emission of the charged scalar, and show that they can exceed those for capture via vector emission, as well as annihilation, by orders of magnitude. This holds even for very small values of the DM coupling to the charged scalar, and remains true in the limit of global symmetry. We then compute the DM thermal freeze-out, and find that the capture into meta-stable bound states via emission of a charged scalar can cause a late period of significant DM depletion. Our results include analytical expressions in the Coulomb limit, and are readily generalisable to non-Abelian interactions. We expect them to have implications for Higgs-portal scenarios of multi-TeV WIMP DM, as well as scenarios that feature dark Higgses or (darkly-)charged inert scalars, including models of self-interacting DM.
Prolay Chanda🇺🇸 · Saleh Hamdan🇺🇸 · James Unwin🇺🇸
It is quite conceivable that dark matter freeze-out occurred during an early period of matter domination, in which case the evolution and relic abundance differ from standard freeze-out calculations which assume a radiation dominated universe. Here we re-examine the classic models in which dark matter interactions with the Standard Model are mediated via either the Higgs or boson in the context of matter dominated freeze-out. We highlight that while these classic models are largely excluded by searches in the radiation dominated case, matter dominated freeze-out can relax these limits and thus revive the Higgs and portals. Additionally, we discuss the distinctions between matter dominated freeze-out and decoupling during the transition from matter domination to radiation domination, and we comment on the parameter regimes which lead to non-negligible dark matter production during this transition.
Mingyang Sun🇺🇸 · Ying Chen🇨🇳 · Gen Wang🇺🇸 · Andrei Alexandru🇺🇸 · Shao-Jing Dong🇺🇸 · Terrence Draper🇺🇸 · Jacob Fallica🇺🇸 · Ming Gong🇨🇳 · Frank X. Lee🇺🇸 · Anyi Li🇺🇸 · Jian Liang🇺🇸 · Keh-Fei Liu🇺🇸 · Nilmani Mathur🇮🇳 · Yi-Bo Yang🇨🇳
The Roper state is extracted with valence overlap fermions on a -flavor domain-wall fermion lattice (spacing fm and MeV) using both the Sequential Empirical Bayes (SEB) method and the variational method. The results are consistent, provided that a large smearing-size interpolation operator is included in the variational calculation to have better overlap with the lowest radial excitation. Similar calculations carried out for an anisotropic clover lattice with similar parameters find the Roper MeV higher than that of the overlap fermion. The fact that the prediction of the Roper state by overlap fermions is consistently lower than those of clover fermions, chirally improved fermions, and twisted-mass fermions over a wide range of pion masses has been dubbed a "Roper puzzle." To understand the origin of this difference, we study the hairpin -diagram in the isovector scalar meson () correlator in the quenched approximation. Comparing the correlators for clover and overlap fermions, at a pion mass of 290 MeV, we find that the spectral weight of the ghost state with clover fermions is smaller than that of the overlap at fm and fm, whereas the whole correlators of clover and overlap at fm coincide within errors. This suggests that chiral symmetry is restored for clover at fm and that the Roper should come down at and below this . We conclude that this work supports a resolution of the "Roper puzzle" due to -graph type chiral dynamics. This entails coupling to higher components in the Fock space (e.g. , states) to induce the effective flavor-spin interaction between quarks as prescribed in the chiral quark model, resulting in the parity-reversal pattern as observed in the experimental excited states of and .
Lev Lipatov was a giant in the field of strong interactions and a dominant force in high-energy QCD for many decades. His work deeply influenced both how we think about QCD and how we perform calculations in the theory. Below we describe the work in two related research directions: the physics of parton saturation and proton spin at small . Both developments would have been impossible without Lipatov's groundbreaking work. Saturation physics would not have happened without the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation. The recent progress in our theoretical understanding of the proton spin contribution coming from small- partons started with the seminal paper by Kirschner and Lipatov resumming double logarithms of energy in the Reggeon evolution.
Kohei Kamada🇯🇵 · Jun'ya Kume🇯🇵 · Yusuke Yamada🇯🇵 · Jun'ichi Yokoyama🇯🇵
We revisit the gravitational leptogenesis scenario in which the inflaton is coupled to gravity by the Chern-Simons term and the lepton asymmetry is generated through the gravitational anomaly in the lepton number current during inflation. We constrain the possible model parameter space by requiring the absence of ghost modes below the Planck scale, which would suggest the breakdown of the effective theory, and evaluate the net baryon asymmetry for various reheating processes. We find that the mechanism with these requirements is insufficient to explain the observed baryon asymmetry of the Universe for standard reheating scenarios. We show that, however, with the kination scenario realized in e.g. the k- and G-inflation models, a sufficient baryon asymmetry can be generated within a feasible range of the model parameters.
Philipp Isserstedt🇩🇪 · Michael Buballa🇩🇪 · Christian S. Fischer🇩🇪 · Pascal J. Gunkel🇩🇪
We summarize our results on baryon number fluctuations at nonzero temperature and chemical potential. They are obtained from solutions of a coupled set of Dyson-Schwinger equations for the quark and gluon propagators of QCD in Landau gauge with quark flavors. In comparison with preliminary STAR data, our results are compatible with a critical endpoint at large chemical potential and a freeze-out line that bends below it.
Abdel Nasser Tawfik (Nile U., ECTP and Johann Wolfgang Goethe-Universitat)🇪🇬 · Carsten Greiner (Johann Wolfgang Goethe-Universitat)🇩🇪
For temperatures ranging from a few MeV up to TeV and energy density up to GeV/fm, the bulk viscosity is calculated in non-perturbation (up, down, strange, charm, and bottom) and perturbation theories with up, down, strange, charm, bottom, and top quark flavors, at vanishing baryon-chemical potential. To these calculations, results deduced from the effective QCD-like model, the Polyakov linear-sigma model (PLSM), are also integrated in. The PLSM merely comes up with essential contributions for the vacuum and thermal condensations of the gluons and the quarks (up, down, strange, and charm flavors). Furthermore, the thermal contributions of the photons, neutrinos, charged leptons, electroweak particles, and scalar Higgs boson, are found very significant along the entire range of and and therefore could be well integrated in. We present the dimensionless quantity , where is a perturbative scale and is the entropy density and conclude that exponentially decreases with increasing . We also conclude that the resulting with the non-perturbative and perturbative QCD contributions non-monotonically increases with increasing . But with nearly-entire standard model contributions considered in the present study, almost-linearly increases with increasing . Apparently, these results offer a great deal to explore in astrophysics, cosmology, and nuclear collisions.
C. Ayala🇨🇱 · S. V. Mikhailov🇷🇺 · A. V. Pimikov🇨🇳 · N. G. Stefanis🇩🇪
We consider the lightcone sum-rule (LCSR) description of the pion-photon transition form factor in combination with the renormalization group of QCD. The emerging scheme represents a certain version of Fractional Analytic Perturbation Theory and significantly extends the applicability domain of perturbation theory towards lower momenta GeV. We show that the predictions calculated herewith agree very well with the released preliminary data of the BESIII experiment, which have very small errors just in this region, while the agreement with other data at higher is compatible with the LCSR predictions obtained recently by one of us using fixed-order perturbation theory.
V. P. Goncalves🇧🇷 · G. Sampaio dos Santos🇧🇷 · C. R. Sena🇧🇷
In this paper we present a comprehensive analysis of the exclusive heavy quark photoproduction in , and collisions at LHC and FCC energies using the color dipole formalism and taking into account of nonlinear corrections to the QCD dynamics. We estimate the rapidity distributions and cross sections for the charm and bottom production considering three phenomenological models for the dipole-proton scattering amplitude that are able to describe the HERA data. Our results indicate that a future experimental analysis of this process is feasible, which will allow us to improve our understanding of the QCD dynamics.
The present practice of Asymptotic Safety in gravity is in conflict with explicit calculations in low energy quantum gravity. This raises the question of whether the present practice meets the Weinberg condition for Asymptotic Safety. I argue, with examples, that the running of and found in Asymptotic Safety are not realized in the real world, with reasons which are relatively simple to understand. A comparison/contrast with quadratic gravity is also given, which suggests a few obstacles that must be overcome before the Lorentzian version of the theory is well behaved. I make a suggestion on how a Lorentzian version of Asymptotic Safety could potentially solve these problems.
* 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.