HEP Phenomenology·hep-ph

Mon·May 9, 2016Monday·May 9, 2016

15 papers—12 primary·3 cross-listed·reconstructed*

01*
Direct and Semi-Direct Approaches to Lepton Mixing with a Massless Neutrino
Stephen F. King🇬🇧 · Patrick Otto Ludl🇬🇧
We discuss the possibility of enforcing a massless Majorana neutrino in the direct and semi-direct approaches to lepton mixing, in which the PMNS matrix is partly predicted by subgroups of a discrete family symmetry, extending previous group searches up to order 1535. We find a phenomenologically viable scheme for the semi-direct approach based on $Q (648)$ which contains $Δ (27)$ and the quaternion group as subgroups. This leads to novel predictions for the first column of the PMNS matrix corresponding to a normal neutrino mass hierarchy with $m_{1} = 0$ , and sum rules for the mixing angles and phase which are characterised by the solar angle being on the low side $θ_{12} \sim 3 1^{\circ}$ and the Dirac (oscillation) CP phase $δ$ being either about $\pm 4 5^{\circ}$ or $\pm π$ .
hep-phJHEP(2016)·24 citations
02*
Matched predictions for the $b b ˉ H$ cross section at the 13 TeV LHC
Marco Bonvini🇬🇧 · Andrew S. Papanastasiou🇬🇧 · Frank J. Tackmann🇩🇪
We present up-to-date matched predictions for the $b b ˉ H$ inclusive cross section at the LHC at $s = 13$ TeV. Using a previously developed method, our predictions consistently combine the complete NLO contributions that are present in the 4-flavor scheme calculation, including finite b-quark mass effects as well as top-loop induced $Y_{b} Y_{t}$ interference contributions, with the resummation of collinear logarithms of $m_{b} / m_{H}$ as present in the 5-flavor scheme calculation up to NNLO. We provide a detailed estimate of the perturbative uncertainties of the matched result by examining its dependence on the factorization and renormalization scales, the scale of the Yukawa coupling, and also the low b-quark matching scale in the PDFs. We motivate the use of a central renormalization scale of $m_{H}$ /2, which is halfway between the values typically chosen in the 4-flavor and 5-flavor scheme calculations. We evaluate the parametric uncertainties due to the PDFs and the b-quark mass, and in particular discuss how to systematically disentangle the parametric $m_{b}$ dependence and the unphysical b-quark matching scale dependence. Our best prediction for the $b b ˉ H$ production cross section in the Standard Model at 13 TeV and for $m_{H}$ = 125 GeV is $σ (b b ˉ H) = 0.52 pb [1 \pm 9.6% (perturbative)_{- 3.6%}^{+ 2.9%} (parametric)]$ . We also provide predictions for a range of Higgs masses $m_{H} \in [50, 750]$ GeV. Our method to compute the matched prediction and to evaluate its uncertainty can be readily applied to other heavy-quark-initiated processes at the LHC.
hep-phhep-exJHEP(2016)·109 citations
03*
Measuring gravitational effects on antimatter in space
Giovanni Maria Piacentino🇮🇹 · Anthony Palladino🇮🇹 · Graziano Venanzoni🇮🇹
We propose an experimental test of the gravitational interaction with antimatter by measuring the branching fraction of the CP~violating decay $K_{L} \to π^{+} π^{-}$ in space. We show that at the altitude of the International Space Station, gravitational effects may change the level of CP~violation such that a 5 $σ$ discrimination may be obtained by collecting the $K_{L}$ produced by the cosmic proton flux within a few years.
hep-phhep-exPhys.Dark Univ.(2016)·7 citations
04*
The Solar Solution: Tracking the Sun with Low Energy Neutrinos
Nicole Hartman🇺🇸 · Stephen Sekula🇺🇸
As neutrinos become a significant background for projected dark matter experiments, the community will become concerned with determining if events counted in a dark matter experiment are good dark matter candidates or low-energy neutrinos from astrophysical sources. We investigate the feasibility of using neutrino-electron scattering in a terrestrial detector medium as a means to determine the flight direction of the original, low-energy solar neutrino.Using leading-order weak interactions in the Standard Model and constrains from energy and momentum conservation, we developed a simple simulation that suggests that 68% of the time the ejected electron would be within 0.99 radians of the incident neutrino's direction. This suggests that it may be fruitful to pursue low-energy neutrino detection capability that can utilize such ejected electrons.
hep-phhep-ex1 citation
05*
Landau gauge Yang-Mills correlation functions
Anton K. Cyrol🇩🇪 · Leonard Fister🇫🇷 · Mario Mitter🇩🇪 · Jan M. Pawlowski🇩🇪 · Nils Strodthoff🇺🇸
We investigate Landau gauge $S U (3)$ Yang-Mills theory in a systematic vertex expansion scheme for the effective action with the functional renormalisation group. Particular focus is put on the dynamical creation of the gluon mass gap at non-perturbative momenta and the consistent treatment of quadratic divergences. The non-perturbative ghost and transverse gluon propagators as well as the momentum-dependent ghost-gluon, three-gluon and four-gluon vertices are calculated self-consistently with the classical action as only input. The apparent convergence of the expansion scheme is discussed and within the errors, our numerical results are in quantitative agreement with available lattice results.
hep-phhep-lathep-thPRD(2016)·269 citations
06*
Boosted scalar confronting 750 GeV di-photon excess
Yun Jiang🇩🇰 · Lingfeng Li🇺🇸 · Rui Zheng🇺🇸
We consider the di-photon signal arises from two bunches of collimated photon jets emitting from a pair of highly boosted scalars. Following the discussion of detecting the photon jets at the collider, we extend the two-Higgs-doublet model (2HDM) by adding a gauge singlet scalar. To explain the di-photon excess which is recently observed at the first 13 TeV run of the LHC, the mixing between the heavy doublet state and the newly added singlet is crucially needed. After the mixing, one can have a heavy Higgs state $Y_{2}$ at 750 GeV and a very singlet-like scalar $Y_{1}$ of sub-GeV, which would be highly boosted through the $Y_{2}$ decay. Both real singlet and complex singlet extension are studied. It turns out that only the complex model can yield the 1-10 fb cross section in the di-photon final state in accompany with the decay length of the order of 1 m for the $Y_{1}$ . This complex model parametrically predicts the width of 750 GeV resonance $≳ 1$ GeV. In addition, the pseudoscalar component of the singlet in this model is naturally stable and hence could be a dark matter candidate.
hep-ph12 citations
07*
Magnetic shift of the chemical freezeout and electric charge fluctuations
Kenji Fukushima🇯🇵 · Yoshimasa Hidaka🇯🇵
We discuss the effect of a strong magnetic field on the chemical freezeout points in the ultrarelativistic heavy-ion collision. As a result of the inverse magnetic catalysis or the magnetic inhibition, the crossover onset to hot and dense matter out of quarks and gluons should be shifted to a lower temperature. To quantify this shift we employ the hadron resonance gas model and an empirical condition for the chemical freezeout. We point out that the charged particle abundances are significantly affected by the magnetic field so that the electric charge fluctuation is largely enhanced especially at high baryon density. The charge conservation partially cancels the enhancement but our calculation shows that the electric charge fluctuation and the charge chemical potential could serve as a magnetometer. We find that the fluctuation exhibits a crossover behavior rapidly increased for eB >~ (0.4GeV)^2, while the charge chemical potential has better sensitivity to the magnetic field.
hep-phnucl-thPRL(2016)·46 citations
08*
Lepton Flavor Violation in the singlet-triplet scotogenic model
Paulina Rocha-Moran🇪🇸 · Avelino Vicente🇪🇸
We investigate lepton flavor violation (LFV) in the the singlet-triplet scotogenic model in which neutrinos acquire non-zero masses at the 1-loop level. In contrast to the most popular variant of this setup, the singlet scotogenic model, this version includes a triplet fermion as well as a triplet scalar, leading to a scenario with a richer dark matter phenomenology. Taking into account results from neutrino oscillation experiments, we explore some aspects of the LFV phenomenology of the model. In particular, we study the relative weight of the dipole operators with respect to other contributions to the LFV amplitudes and determine the most constraining observables. We show that in large portions of the parameter space, the most promising experimental perspectives are found for LFV 3-body decays and for coherent $μ - e$ conversion in nuclei.
hep-phJHEP(2016)·36 citations
09*
Constraints on 750 GeV colorless Q-onia from running couplings
Luis A. Anchordoqui🇺🇸 · Haim Goldberg🇺🇸 · Xing Huang🇹🇼
We present yet another composite model explaining the relatively broad peak in the diphoton invariant mass distribution around 750 GeV recently observed at the LHC experiments. We consider the excess originates in bound states of vector-like fermions Q transforming under the electroweak group (but not QCD) of the standard model and which are also charged under a new SU(N_{TC}) QCD-like confining force. Since the new uncolored fields transform as SU(2) doublets they can acquire a mass through Yukawa interactions with the electroweak Higgs doublet, as quarks and leptons. We parametrize the Q-onium bound state using the Coulomb approximation and give a numerical fit to the diphoton excess consistent with no strong coupling effects up to about 30 TeV, which is the energy scale for next generation colliders. The range of allowed hypercharge Y_Q is given by 2.26 \leq Y_Q \leq 2.53 for N_{\rm TC} =2 and 2.17 \leq Y_Q \leq 2.31 for N_{\rm TC} = 3. The smoking gun for the model would be the discovery of Q-onia decaying into Higgs and Z-boson.
hep-ph5 citations
10*
A determination of mc(mc) from HERA data using a matched heavy-flavor scheme
xFitter Developers' team: Valerio Bertone🇬🇧 · Stefano Camarda🇨🇭 · Amanda Cooper-Sarkar🇬🇧 · Alexandre Glazov🇩🇪 · Agnieszka Luszczak🇵🇱 · Hayk Pirumov🇩🇪 · Ringaile Placakyte🇩🇪 · Klaus Rabbertz🇩🇪 · Voica Radescu🇩🇪 · Juan Rojo🇬🇧 · Andrey Sapranov🇷🇺 · Oleksandr Zenaiev🇩🇪 · Achim Geiser🇩🇪
The charm quark mass is one of the fundamental parameters of the Standard Model Lagrangian. In this work we present a determination of the MSbar charm mass from a fit to the inclusive and charm HERA deep-inelastic structure function data. The analysis is performed within the xFitter framework, with structure functions computed in the FONLL general-mass scheme as implemented in APFEL. In the case of the FONLL-C scheme, we obtain mc(mc) = 1.335 +- 0.043(exp) +0.019 -0.000(param) +0.011 -0.008(mod) +0.033 -0.008(th) GeV. We also perform an analogous determination in the fixed-flavor-number scheme at next-to-leading order, finding mc(mc) = 1.318 +- 0.054(exp) +0.011 -0.010(param) +0.015 -0.019(mod) +0.045 -0.004(th) GeV, compatible with the FONLL-C value. Our results are consistent with previous determinations from DIS data as well as with the PDG world average.
hep-phJHEP(2016)·23 citations
11*
Origin of Mass - Horizons Expanding from the Nambu's Theory
Koichi Yamawaki🇯🇵
Origin of mass may be strong dynamics of matter in the vacuum. Since the initial proposal of Nambu for the origin of the nucleon mass, the dynamical symmetry breaking in the strongly coupled underlying theories has been expanding the horizons in the context of the modern version of the origin of mass beyond the Standard Model (SM). The Nambu-Jona-Lasinio (NJL) model is a typical strong coupling theory with the non-zero critical coupling, in sharp contrast to its precedent model, the Bardeen-Cooper-Schrieffer theory for the superconductor. The non-zero critical coupling is also hidden in the asymptotically free gauge theories including QCD and walking technicolor. As is well known, the NJL model can be cast into the SM Higgs Lagrangian. We show that the SM Higgs Lagrangian is simply rewritten into a form of the (approximately) scale-invariant nonlinear sigma model, with both the chiral symmetry and scale symmetry realized nonlinearly, with the SM Higgs being nothing but the (pseudo-) dilaton. The SM Higgs Lagrangian is further gauge equivalent to the scale-invariant Hidden Local Symmetry (HLS) Lagrangian, s-HLS, having spin 1 bosons hidden in the SM. As the simplest possible underlying theory for the SM Higgs Lagrangian we first discuss the top quark condensate ("top-mode SM"), where the top-mode dilaton is the 125 GeV Higgs. We then discuss the walking technicolor having near infrared conformality, whose effective theory is the s-HLS model precisely the same as the SM Higgs Lagrangian (with larger chiral symmetry), where the 125 GeV Higgs is successfully identified with the techidilaton.
hep-phhep-lathep-thPTEP(2016)·6 citations
12*
Flavor Mixing Phenomenology in Supersymmetric Models
Muhammad Rehman🇪🇸
This dissertation investigates the flavor mixing effects in supersymmetric models on electroweak precision observables, Higgs boson mass predictions, B-physics observables, quark flavor violating Higgs decays, lepton flavor violating charged lepton decays and lepton flavor violating Higgs decays. The flavor mixing effects are studied in model independent way i.e. by putting off-diagonal entries in the sfermion mass matrix by hand as well as in the minimal flavor violating constrained MSSM, where mixing can originate from CKM matrix in the case of squarks and from PMNS matrix in the case of sleptons. We found that flavor mixing can have large impact to some observables, enabling us to put new constraints on parameter space in supersymmetric models.
hep-ph0 citations
13*
A Conformal Fixed-Point Equation for the Effective Average Action
Oliver J. Rosten
A Legendre transform of the recently discovered conformal fixed-point equation is constructed, providing an unintegrated equation encoding full conformal invariance within the framework of the effective average action.
↳ hep-thcond-mat.stat-mechhep-phInt.J.Mod.Phys.A(2019)·15 citations
14*
Gluon bound state and asymptotic freedom derived from the Bethe--Salpeter equation
Hitoshi Fukamachi🇯🇵 · Kei-Ichi Kondo🇯🇵 · Shogo Nishino🇯🇵 · Toru Shinohara🇯🇵
In this paper we study the two-body bound states for gluons and ghosts in a massive Yang-Mills theory which is obtained by generalizing the ordinary massless Yang-Mills theory in a manifestly Lorentz covariant gauge. First, we give a systematic derivation of the coupled Bethe-Salpeter equations for gluons and ghosts by using the Cornwall-Jackiw-Tomboulis effective action of the composite operators within the framework of the path integral quantization. Then, we obtain the numerical solutions for the Bethe-Salpeter amplitude representing the simultaneous bound states of gluons and ghosts by solving the homogeneous Bethe-Salpeter equation in the ladder approximation. We study how the inclusion of ghosts affects the two-gluon bound states in the cases of the standing and running gauge coupling constant. Moreover, we show explicitly that the approximate solutions obtained for the gluon-gluon amplitude are consistent with the ultraviolet asymptotic freedom signaled by the negative $β$ function.
↳ hep-thhep-phPTEP(2017)·3 citations
15*
Hamiltonian YM 2+1: note on point splitting regularization
Hermann Schulz (Institut für Theoretische Physik, Leibniz Universität Hannover)🇩🇪
The Hamiltonian of 2+1 dimensional Yang Mills theory was derived by Karabali, Kim and Nair by using point splitting regularization. But in calculating e.g. the vacuum wave functional this scheme was left in favour of arguments. Here we follow up a conjecture of Leigh, Minic and Yelnikov of how this gap might be filled by including all positive powers of the regularization parameter ( $\ep \to + 0$ ). Admittedly, though we concentrate on the ground state in the large $N$ limit, only two such powers could be included due to the increasing complexity of the task.
↳ hep-thhep-ph0 citations

* 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.