HEP Phenomenology·hep-ph

Fri·Aug 28, 2015Friday·August 28, 2015

19 papers—13 primary·6 cross-listed·reconstructed*

01*
The Effect of Final HERA inclusive Cross Section Data on MMHT2014 PDFs
R.S. Thorne🇬🇧 · L.A. Harland-Lang🇬🇧 · A.D. Martin🇬🇧 · P. Motylinski🇬🇧
We investigate the effect of including the HERA run I + II combined cross section data on the MMHT2014 PDFs. We present the fit quality within the context of the global fit and when only the HERA data are included. We examine the changes in both the central values and uncertainties in the PDFs. We find that the prediction for the data is good, and only relatively small improvements in $χ^{2}$ and changes in the PDFs are obtained with a refit at both NLO and NNLO. PDF uncertainties are slightly reduced. There is a small dependence of the fit quality on the value of $Q_{m i n}^{2}$ .
hep-phhep-exPoS(2015)·11 citations
02*
Dark Matter and Global Symmetries
Yann Mambrini🇫🇷 · Stefano Profumo🇺🇸 · Farinaldo S. Queiroz🇩🇪
General considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. Assuming the validity of such considerations, we derive stringent bounds from gamma-ray, X-ray, cosmic-ray, neutrino, and CMB data on models that invoke global symmetries to stabilize the dark matter particle. We compute up-to-date, robust model-independent limits on the dark matter lifetime for a variety of Planck-scale suppressed dimension-five effective operators. We then specialize our analysis and apply our bounds to specific models including the Two-Higgs-Doublet, Left-Right, Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. {Assuming that (i) global symmetries are broken at the Planck scale, that (ii) the non-renormalizable operators mediating dark matter decay have $O (1)$ couplings, that (iii) the dark matter is a singlet field, and that (iv) the dark matter density distribution is well described by a NFW profile}, we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (keV-TeV), including the WIMP regime.
hep-phastro-ph.COPLB(2016)·148 citations
03*
An alternative interpretation for cosmic ray peaks
Doojin Kim🇺🇸 · Jong-Chul Park🇰🇷
We propose an alternative mechanism based upon dark matter (DM) interpretation for anomalous peak signatures in cosmic ray measurements, assuming an extended dark sector with two DM species. This is contrasted with previous effort to explain various line-like cosmic-ray excesses in the context of DM models where the relevant DM candidate directly annihilates into Standard Model (SM) particles. The heavier DM is assumed to annihilate to an on-shell intermediate state. As the simplest choice, it decays directly into the lighter DM along with an unstable particle which in turn decays to a pair of SM states corresponding to the interesting cosmic anomaly. We show that a sharp continuum energy peak can be readily generated under the proposed DM scenario, depending on dark sector particle mass spectra. Remarkably, such a peak is robustly identified as half the mass of the unstable particle. Furthermore, other underlying mass parameters are analytically related to the shape of energy spectrum. We apply this idea to the two well-known line excesses in the cosmic photon spectrum: 130 GeV gamma-ray line and 3.5 keV X-ray line. Each observed peak spectrum is well-reproduced by theoretical expectation predicated upon our suggested mechanism, and moreover, our resulting best fits provide rather improved chi-square values.
hep-phPLB(2015)·12 citations
04*
An Effective Field Theory for Jet Processes
Thomas Becher🇨🇭 · Matthias Neubert🇩🇪 · Lorena Rothen🇨🇭 · Ding Yu Shao🇨🇭
Processes involving narrow jets receive perturbative corrections enhanced by logarithms of the jet opening angle and the ratio of the energies inside and outside the jets. Analyzing cone-jet processes in effective field theory, we find that in addition to soft and collinear fields their description requires degrees of freedom which are simultaneously soft and collinear to the jets. These collinear-soft particles can resolve individual collinear partons, leading to a complicated multi-Wilson-line structure of the associated operators at higher orders. Our effective field theory provides, for the first time, a factorization formula for a cone-jet process, which fully separates the physics at different energy scales. Its renormalization-group equations control all logarithmically enhanced higher-order terms, in particular also the non-global logarithms.
hep-phPRL(2016)·160 citations
05*
On the proton charge extensions
Jesse R. Stryker🇺🇸 · Gerald A. Miller🇺🇸
We examine how corrections to $S$ -state energy levels, $E_{n S}$ , in hydrogenic atoms due to the finite proton size are affected by moments of the proton charge distribution. The corrections to $E_{n S}$ are computed moment by moment. The results demonstrate that the next-to-leading order term in the expansion is of order $r_{p} / a_{B}$ times the size of the leading order $⟨ r_{p}^{2} ⟩$ term. Our analysis thus dispels any concern that the larger relative size of this term for muonic hydrogen versus electronic hydrogen might account for the current discrepancy of proton radius measurements extracted from the two systems. Furthermore, the next-to-leading order term in powers of $r_{p} / a_{B}$ that we derive from a dipole proton form factor is proportional to $⟨ r_{p}^{3} ⟩$ , rather than $⟨ r_{p}^{4} ⟩$ as would be expected from the scalar nature of the form factor. The dependence of the finite-size correction on $⟨ r_{p}^{3} ⟩$ and higher odd-power moments is shown to be a general result for any spherically symmetric proton charge distribution. A method for computing the moment expansion of the finite-size correction to arbitrary order is introduced and the results are tabulated for principal quantum numbers up to $n = 7$ .
hep-phnucl-exnucl-thphysics.atom-phPRA(2016)·4 citations
06*
Shift Symmetry and Higgs Inflation in Supergravity with Observable Gravitational Waves
G. Lazarides🇬🇷 · C. Pallis🇪🇸
We demonstrate how to realize within supergravity a novel chaotic-type inflationary scenario driven by the radial parts of a conjugate pair of Higgs superfields causing the spontaneous breaking of a grand unified gauge symmetry at a scale assuming the value of the supersymmetric grand unification scale. The superpotential is uniquely determined at the renormalizable level by the gauge symmetry and a continuous R symmetry. We select two types of Kahler potentials, which respect these symmetries as well as an approximate shift symmetry. In particular, they include in a logarithm a dominant shift-symmetric term proportional to a parameter c- together with a small term violating this symmetry and characterized by a parameter c+. In both cases, imposing a lower bound on c-, inflation can be attained with subplanckian values of the original inflaton, while the corresponding effective theory respects perturbative unitarity for r+-=c+/c-<1. These inflationary models do not lead to overproduction of cosmic defects, are largely independent of the one-loop radiative corrections and accommodate, for natural values of r+-, observable gravitational waves consistently with all the current observational data. The inflaton mass is mostly confined in the range (3.7-8.1)x10^10 GeV.
hep-phastro-ph.COhep-thJHEP(2015)·30 citations
07*
Closing in on compressed gluino-neutralino spectra at the LHC
Guillaume Chalons🇫🇷 · Dipan Sengupta🇫🇷
A huge swath of parameter space in the context of the Minimal Supersymmetric Standard Model (MSSM) has been ruled at after run I of the LHC. Various exclusion contours in the $m_{g ~} - \m_{χ ~_{1}^{0}}$ plane were derived by the experimental collaborations, all based on three-body gluino decay topologies. These limits are however extremely model dependent and do not always reflect the level of exclusion. If the gluino-neutralino spectrum is compressed, then the current mass limits can be drastically reduced. In such situations, the radiative decay of the gluino $\gino \ra g \neut 1$ can be dominant and used as a sensitive probe of small mass splittings. We examine the sensitivity of constraints of some Run I experimental searches on this decay after recasting them within the \texttt{MadAnalysis5} framework. The recasted searches are now part of the \texttt{MadAnalysis5} Public Analysis Database. We also design a dedicated search strategy and investigate its prospects to uncover this decay mode of the gluino at run II of the LHC. We emphasize that a multijet search strategy may be more sensitive than a monojet one, even in the case of very small mass differences.
hep-phhep-exJHEP(2015)·10 citations
08*
String Theory at LHC Using Supersymmetry Production From String Balls
Gouranga C. Nayak
If extra dimensions are found in the second run of LHC in the $pp$ collisions at $s$ = 14 TeV then the string scale can be $\sim$ TeV, and we should produce string balls at LHC. In this paper we study supersymmetry (squark and gluino) production from string balls at LHC in $pp$ collisions at $s$ = 14 TeV and compare that with the parton fusion results using pQCD. We find significant squark and gluino production from string balls at LHC which is comparable to parton fusion pQCD results. Hence, in the absence of black hole production at LHC, an enhancement in supersymmetry production can be a signature of TeV scale string physics at LHC.
hep-phhep-th0 citations
09*
Bosonic seesaw mechanism in a classically conformal extension of the Standard Model
Naoyuki Haba🇯🇵 · Hiroyuki Ishida🇯🇵 · Nobuchika Okada🇺🇸 · Yuya Yamaguchi🇯🇵
We suggest the so-called bosonic seesaw mechanism in the context of a classically conformal $U (1)_{B - L}$ extension of the Standard Model with two Higgs doublet fields. The $U (1)_{B - L}$ symmetry is radiatively broken via the Coleman-Weinberg mechanism, which also generates the mass terms for the two Higgs doublets through quartic Higgs couplings. Their masses are all positive but, nevertheless, the electroweak symmetry breaking is realized by the bosonic seesaw mechanism. Analyzing the renormalization group evolutions for all model couplings, we find that a large hierarchy among the quartic Higgs couplings, which is crucial for the bosonic seesaw mechanism to work, is dramatically reduced toward high energies. Therefore, the bosonic seesaw is naturally realized with only a mild hierarchy, if some fundamental theory, which provides the origin of the classically conformal invariance, completes our model at some high energy, for example, the Planck scale. We identify the regions of model parameters which satisfy the perturbativity of the running couplings and the electroweak vacuum stability as well as the naturalness of the electroweak scale.
hep-phPLB(2016)·32 citations
10*
A model-independent analysis of final-state interactions in \bar B_{d/s}^0 --> J/psi pi pi
J. T. Daub🇩🇪 · C. Hanhart🇩🇪 · B. Kubis🇩🇪
Exploiting $B$ -meson decays for Standard Model tests and beyond requires a precise understanding of the strong final-state interactions that can be provided model-independently by means of dispersion theory. This formalism allows one to deduce the universal pion-pion final-state interactions from the accurately known $π π$ phase shifts and, in the scalar sector, a coupled-channel treatment with the kaon-antikaon system. In this work an analysis of the decays $B ˉ_{d}^{0} \to J / ψ π^{+} π^{-}$ and $B ˉ_{s}^{0} \to J / ψ π^{+} π^{-}$ is presented. We find very good agreement with the data up to 1.05 GeV with a number of parameters reduced significantly compared to a phenomenological analysis. In addition, the phases of the amplitudes are correct by construction, a crucial feature when it comes to studies of $C P$ violation in heavy-meson decays.
hep-phhep-exJHEP(2016)·113 citations
11*
Implications of the first AMS-02 antiproton data for dark matter
Hong-Bo Jin🇨🇳 · Yue-Liang Wu🇨🇳 · Yu-Feng Zhou🇨🇳
The implications of the first AMS-02 $p ˉ / p$ data for the propagation of cosmic rays and the properties of dark matter (DM) are discussed. Using various diffusive re-acceleration (DR) propagation models, one can derive very conservative upper limits on the DM annihilation cross sections. The limits turned out to be compatible with that from the Ferm-LAT gamma-ray data on the dwarf spheroidal satellite galaxies. The flattening of the $p ˉ / p$ spectrum above $\sim 100$ ~GeV in the current data still leaves some room for TeV scale DM particles. More antiproton data at high kinetic energies are needed to constrain the properties of the DM particles.
hep-phInt.J.Mod.Phys.A(2015)·9 citations
12*
Initial value problem for magnetic field in heavy ion collisions
Kirill Tuchin🇺🇸
When quark-gluon plasma emerges in the wake of a heavy-ion collision, magnetic field created by the valence charges has already permitted the entire interaction region. Evolution of this "initial" field in plasma is governed by Maxwell equations in electrically conducting medium. As the plasma expands external valence charges induce magnetic field that also contributes to the total magnetic field in plasma. We solve the initial value problem describing these processes and argue that the initial magnetic field often dominates over the one induced by the valence charges. In particular, it grows approximately proportional to the collision energy, unlike the induced component, which is energy-independent. As a result, magnetic field has a significant phenomenological influence on quark-gluon plasma at the LHC energies over its entire lifetime.
hep-phPRC(2016)·109 citations
13*
Functional Renormalization Group Study of the Chiral Phase Transition Including Vector and Axial-vector Mesons
Jürgen Eser🇩🇪 · Mara Grahl🇩🇪 · Dirk H. Rischke🇩🇪
The transition in quantum chromodynamics (QCD) from hadronic matter to the quark-gluon plasma (QGP) at high temperatures and/or net-baryon densities is associated with the restoration of chiral symmetry and can be investigated in the laboratory via heavy-ion collisions. We study this chiral transition within the functional renormalization group (FRG) approach applied to the two-flavor version of the extended Linear Sigma Model (eLSM). The eLSM is an effective model for the strong interaction and features besides scalar and pseudoscalar degrees of freedom also vector and axial- vector mesons. We discuss the impact of the quark masses and the axial anomaly on the order of the chiral transition. We also confirm the degeneracy of the masses of chiral partners above the transition temperature. We find that the mass of the $a_{1}$ meson ( $ρ$ meson) decreases (increases) towards the chiral transition.
hep-phhep-thPRD(2015)·43 citations
14*
Scalar mass stability bound in a simple Yukawa-theory from renormalisation group equations
A. Jakovac🇭🇺 · I. Kaposvari🇭🇺 · A. Patkos🇭🇺
Functional Renormalisation Group (FRG) equations are constructed for a simple Yukawa-model with discrete chiral symmetry, including also the effect of a nonzero composite fermion background beyond the conventional scalar condensate. The evolution of the effective potential of the model, generically depending on two invariants, is explored with help of power series expansions. Systematic investigation of the effect of a class of irrelevant operators on the lower (stability) bound allows a non-perturbative extension of the maximal cut-off value consistent with any given mass of the scalar field.
↳ hep-thhep-phMod.Phys.Lett.A(2016)·19 citations
15*
Primordial scalar power spectrum from the Euclidean Big Bounce
Susanne Schander🇩🇪 · Aurélien Barrau🇫🇷 · Boris Bolliet🇫🇷 · Julien Grain🇫🇷 · Linda Linsefors🇫🇷 · Jakub Mielczarek🇫🇷
In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of an Euclidean phase accompanying the non-singular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power.
↳ gr-qcastro-ph.COhep-phPRD(2016)·51 citations
16*
Dissipative Charged Fluid in a Magnetic Field
Navid Abbasi🇮🇷 · Ali Davody🇮🇷
We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes in presence of magnetic field. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.
↳ hep-thhep-phnucl-thPLB(2016)·4 citations
17*
Axion cosmology, lattice QCD and the dilute instanton gas
S. Borsanyi🇩🇪 · M. Dierigl🇩🇪 · Z. Fodor🇩🇪 · S.D. Katz🇭🇺 · S.W. Mages🇩🇪 · D. Nogradi🇭🇺 · J. Redondo🇪🇸 · A. Ringwald🇩🇪 · K.K. Szabo🇩🇪
Axions are one of the most attractive dark matter candidates. The evolution of their number density in the early universe can be determined by calculating the topological susceptibility $χ (T)$ of QCD as a function of the temperature. Lattice QCD provides an ab initio technique to carry out such a calculation. A full result needs two ingredients: physical quark masses and a controlled continuum extrapolation from non-vanishing to zero lattice spacings. We determine $χ (T)$ in the quenched framework (infinitely large quark masses) and extrapolate its values to the continuum limit. The results are compared with the prediction of the dilute instanton gas approximation (DIGA). A nice agreement is found for the temperature dependence, whereas the overall normalization of the DIGA result still differs from the non-perturbative continuum extrapolated lattice results by a factor of order ten. We discuss the consequences of our findings for the prediction of the amount of axion dark matter.
↳ hep-lathep-phPLB(2016)·167 citations
18*
Non-perturbative tests of continuum HQET through small-volume two-flavour QCD
P. Fritzsch🇪🇸 · N. Garron🇬🇧 · J. Heitger🇩🇪
We study the heavy quark mass dependence of selected observables constructed from heavy-light meson correlation functions in small-volume two-flavour lattice QCD after taking the continuum limit. The light quark mass is tuned to zero, whereas the range of available heavy quark masses $m_{h}$ covers a region extending from around the charm to beyond the bottom quark mass scale. This allows entering the asymptotic mass-scaling regime as $1/ m_{h} \to 0$ and performing well-controlled extrapolations to the infinite-mass limit. Our results are then compared to predictions obtained in the static limit of continuum Heavy Quark Effective Theory (HQET), in order to verify non-perturbatively that HQET is an effective theory of QCD. While in general we observe a nice agreement at the few-% level, we find it to be less convincing for the small-volume pseudoscalar decay constant when perturbative matching is involved.
↳ hep-lathep-phJHEP(2016)·10 citations
19*
Prospects for improving the LHC W boson mass measurement with forward muons
Giuseppe Bozzi🇮🇹 · Luca Citelli🇮🇹 · Mika Vesterinen🇩🇪 · Alessandro Vicini🇮🇹
Measurements of the $W$ boson mass are planned by the ATLAS and CMS experiments, but for the time being, these may be unable to compete with the current world average precision of 15~MeV, due to uncertainties in the PDFs. We discuss the potential of a measurement by the LHCb experiment based on the charged lepton transverse momentum $p_{T}^{ℓ}$ spectrum in $W \to μν$ decays. The unique forward acceptance of LHCb means that the PDF uncertainties would be anti-correlated with those of $p_{T}^{ℓ}$ based measurements by ATLAS and CMS. We compute an average of ATLAS, CMS and LHCb measurements of $m_{W}$ from the $p_{T}^{ℓ}$ distribution. Considering PDF uncertainties, this average is a factor of 1.3 more precise than an average of ATLAS and CMS alone. Despite the relatively low rate of $W$ production in LHCb, we estimate that with the Run-II dataset, a measurement could be performed with sufficient experimental precision to exploit this anti-correlation in PDF uncertainties. The modelling of the lepton-pair transverse momentum distribution in the neutral current Drell-Yan process could be a limiting factor of this measurement and will deserve further studies.
↳ hep-exhep-phEPJC(2015)·52 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.