HEP Phenomenology·hep-ph

Mon·Nov 2, 2015Monday·November 2, 2015

17 papers—11 primary·6 cross-listed·reconstructed*

01*
Recent developments in heavy flavor probes in lattice QCD
Anthony Francis🇨🇦
The analysis of heavy flavor lattice correlation functions to obtain insights into transport phenomena and bound state dissociation patterns is a difficult and interesting challenge from the point of view of lattice QCD spectroscopy. In this contribution to "Hard Probes 2015", the recent developments and advances from different lattice efforts to determine the relevant spectral properties will be reviewed and discussed. The difficulties underlying this line of research will be highlighted and the obtained results assessed. Among others, results on the dissociation of charm systems and bottomonia, as well as the diffusion of heavy quarks will be addressed.
hep-phhep-latnucl-thNucl.Part.Phys.Proc.(2016)·0 citations
02*
The CP-Violating pMSSM
Joshua Berger🇺🇸 · Matthew W. Cahill-Rowley🇺🇸 · Diptimoy Ghosh🇮🇹 · JoAnne L. Hewett🇺🇸 · Ahmed Ismail🇺🇸 · Thomas G. Rizzo🇺🇸
We investigate the sensitivity of the next generation of flavor-based low-energy experiments to probe the supersymmetric parameter space in the context of the phenomenological MSSM (pMSSM), and examine the complementarity with direct searches for Supersymmetry at the 13 TeV LHC in a quantitative manner. To this end, we enlarge the previously studied pMSSM parameter space to include all physical non-zero CP-violating phases, namely those associated with the gaugino mass parameters, Higgsino mass parameter, and the tri-linear couplings of the top quark, bottom quark and tau lepton. We find that future electric dipole moment and flavor measurements can have a strong impact on the viability of these models even if the sparticle spectrum is out of reach of the 13 TeV LHC. In particular, the lack of positive signals in future low-energy probes would exclude values of the phases between $O (1 0^{- 2})$ and $O (1 0^{- 1})$ . We also find regions of parameter space where large phases remain allowed due to cancellations. Most interestingly, in some rare processes, such as BR( $B_{s} \to μ^{+} μ^{-}$ ), we find that contributions arising from CP-violating phases can bring the potentially large SUSY contributions into better agreement with experiment and Standard Model predictions.
hep-phhep-exPRD(2016)·16 citations
03*
Automation of non-SUSY two-loop RGEs with PyR@TE: latest developments
Florian Lyonnet🇺🇸
In light of the conspicuous absence of SUSY in the energy range explored by the LHC during run I, non-supersymmetric BSM scenarios are becoming more and more attractive. One key ingredient in exploring such BSM physics are the renormalization group equations (RGEs) that are essential for extrapolating the theory to higher energy scales. Although the two-loop RGEs for a general quantum field theory have been known for some time, it is only recently that their automation has become available in the form of a Python program called PyR@TE. In this talk, I will present the features of PyR@TE as well as the latest developments of the code. In particular, the new ability to deal with sets of fields that have multiple ways of being contracted into a gauge singlet.
hep-ph6 citations
04*
Resummation ambiguities in the Higgs transverse-momentum spectrum in the Standard Model and beyond
Emanuele Bagnaschi🇩🇪 · Robert V. Harlander🇩🇪 · Hendrik Mantler🇨🇭 · Alessandro Vicini🇮🇹 · Marius Wiesemann🇨🇭
We study the prediction for the Higgs transverse momentum distribution in gluon fusion and focus on the problem of matching fixed- and all-order perturbative results. The main sources of matching ambiguities on this distribution are investigated by means of a twofold comparison. On the one hand, we present a detailed qualitative and quantitative comparison of two recently introduced algorithms for determining the matching scale. On the other hand, we apply the results of both methods to three widely used approaches for the resummation of logarithmically enhanced contributions at small transverse momenta: the MC@NLO and POWHEG Monte Carlo approaches, and analytic resummation. While the three sets of results are largely compatible in the low-pT region, they exhibit sizable differences at large pT. We show that these differences can be significantly reduced by suitable modifications of formally subleading terms in the Monte Carlo implementations. We apply our study to the Standard Model Higgs boson and to the neutral Higgs bosons of the Two-Higgs-Doublet Model for representative scenarios of the parameter space, where the top- and bottom-quark diagrams enter the cross section at different strength.
hep-phJHEP(2016)·46 citations
05*
A light particle solution to the cosmic lithium problem
Andreas Goudelis🇦🇹 · Maxim Pospelov🇨🇦 · Josef Pradler🇦🇹
We point out that the cosmological abundance of $^{7}$ Li can be reduced down to observed values if during its formation Big Bang Nucleosynthesis is modified by the presence of light electrically neutral particles $X$ that have substantial interactions with nucleons. We find that the lithium problem can be solved without affecting the precisely measured abundances of deuterium and helium if the following conditions are satisfied: the mass and lifetimes of such particles are bounded by $1.6 MeV \leq m_{X} \leq 20 MeV$ and $few 100 s ≲ τ_{X} ≲ 1 0^{4} s$ , and the abundance times the absorption cross section by either deuterium or $^{7}$ Be are comparable to the Hubble rate, $n_{X} σ_{abs} v \sim H$ , at the time of $^{7}$ Be formation. We include $X$ -initiated reactions into the primordial nucleosynthesis framework, observe that it leads to a substantial reduction of the freeze-out abundances of $^{7}$ Li+ $^{7}$ Be, and find specific model realizations of this scenario. Concentrating on the axion-like-particle case, $X = a$ , we show that all these conditions can be satisifed if the coupling to $d$ -quarks is in the range of $f_{d}^{- 1} \sim TeV^{- 1}$ , which can be probed at intensity frontier experiments.
hep-phastro-ph.COnucl-thPRL(2016)·53 citations
06*
Production of neutrons in the vicinity of the pion pole
B. Z. Kopeliovich🇨🇱 · I. K. Potashnikova🇨🇱 · Ivan Schmidt🇨🇱
High-energy hadronic reactions with proton-to-neutron transitions (and vice versa) with small momentum transfer allow to study the properties of nearly on-shell pions, which cannot be accessed otherwise. We overview the recent results for such processes in deeply inelastic scattering, single and double leading neutron production in pp collisions, including polarization effect. A special attention is paid to the absorption effects, which are found to be much stronger than what has been evaluated previously.
hep-phActa Phys.Polon.Supp.(2015)·2 citations
07*
Neutron capture and the antineutrino yield from nuclear reactors
Patrick Huber🇺🇸 · Patrick Jaffke🇺🇸
We identify a new, flux-dependent correction to the antineutrino spectrum as produced in nuclear reactors. The abundance of certain nuclides, whose decay chains produce antineutrinos above the threshold for inverse beta decay, has a nonlinear dependence on the neutron flux, unlike the vast majority of antineutrino producing nuclides, whose decay rate is directly related to the fission rate. We have identified four of these so-called nonlinear nuclides and determined that they result in an antineutrino excess at low-energies below 3.2MeV, dependent on the reactor thermal neutron flux. We develop an analytic model for the size of the correction and compare it to the results of detailed reactor simulations for various real existing reactors, spanning 3 orders of magnitude in neutron flux. In a typical pressurized water reactor the resulting correction can reach 0.9% of the low energy flux which is comparable in size to other, known low-energy corrections from spent nuclear fuel and the non-equilibrium correction. For naval reactors the nonlinear correction may reach the 10% level.
hep-phhep-exnucl-exnucl-thPRL(2016)·27 citations
08*
Polarization of the top quark as a probe of its chromomagnetic and chromoelectric couplings in single-top production at the Large Hadron Collider
Saurabh D. Rindani🇮🇳 · Pankaj Sharma🇦🇺 · Anthony W. Thomas🇦🇺
We study the sensitivity of the Large Hadron Collider (LHC) to top quark chromomagnetic (CMDM) and chromoelectric (CEDM) dipole moments and $W t b$ effective couplings in single-top production in association with a $W^{-}$ boson, followed by semileptonic decay of the top. We calculate the top polarization and the effects of these anomalous couplings on it at two centre-of-mass (cm) energies, 8 TeV and 14 TeV. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame, without requiring reconstruction of the rest frame of the top, and study the effect of the anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top-quark couplings. The Wt single-top production mode helps to isolate the anomalous $tt g$ and $W t b$ couplings, in contrast to top-pair production and other single-top production modes, where other new-physics effects can also contribute. We determine individual limits on the dominant couplings, viz., the real part of the CMDM $R e ρ_{2}$ , the imaginary part of the CEDM $I m ρ_{3}$ , and the real part of the tensor Wtb coupling $R e f_{2 r}$ , which may be obtained by utilizing these asymmetries at the LHC. We also obtain simultaneous limits on pairs of these couplings taking two couplings to be non-zero at a time.
hep-phPoS(2016)·5 citations
09*
Interplay of gaugino (co)annihilation processes in the context of a precise relic density calculation
Julia Harz🇫🇷 · Björn Herrmann🇫🇷 · Michael Klasen🇩🇪 · Karol Kovařík🇩🇪 · Patrick Steppeler🇩🇪
The latest Planck data allow one to determine the dark matter relic density with previously unparalleled precision. In order to achieve a comparable precision on the theory side, we have calculated the full $O (α_{s})$ corrections to the most relevant annihilation and coannihilation processes for relic density calculations within the Minimal Supersymmetric Standard Model (MSSM). The interplay of these processes is discussed. The impact of the radiative corrections on the resulting relic density is found to be larger than the experimental uncertainty of the Planck data.
hep-phPoS(2015)·0 citations
10*
Inverse magnetic catalysis from the properties of the QCD coupling in a magnetic field
Alejandro Ayala🇲🇽 · C. A. Dominguez🇿🇦 · L. A. Hernandez🇿🇦 · M. Loewe🇿🇦 · R. Zamora🇨🇱
We compute the vacuum one-loop quark-gluon vertex correction at zero temperature in the presence of a magnetic field. From the vertex function we extract the effective quark-gluon coupling and show that it grows with increasing magnetic field strength. The effect is due to a subtle competition between the color charge associated to gluons and the color charge associated to quarks, the former being larger than the latter. In contrast, at high temperature the effective thermo-magnetic coupling results exclusively from the contribution of the color charge associated to quarks. This produces a decrease of the coupling with increasing field strength. We interpret the results in terms of a geometrical effect whereby the magnetic field induces, on average, a closer distance between the (electrically charged) quarks and antiquarks. At high temperature, since the effective coupling is proportional only to the color charge associated to quarks, such proximity with increasing field strength makes the effective coupling decrease due to asymptotic freedom. In turn, this leads to a decreasing quark condensate. In contrast, at zero temperature both the effective strong coupling and the quark condensate increase with increasing magnetic field. This is due to the color charge associated to gluons dominating over that associated to quarks, with both having the opposite sign. Thus, the gluons induce a kind of screening of the quark color charge, in spite of the quark-antiquark proximity. The implications of these results for the inverse magnetic catalysis phenomenon are discussed.
hep-phhep-latnucl-thPLB(2016)·81 citations
11*
On the Alignment Limit of the NMSSM Higgs Sector
Marcela Carena🇺🇸 · Howard E. Haber🇺🇸 · Ian Low🇺🇸 · Nausheen R. Shah🇺🇸 · Carlos E. M. Wagner🇺🇸
The Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM) with a Higgs boson of mass 125 GeV can be compatible with stop masses of order of the electroweak scale, thereby reducing the degree of fine-tuning necessary to achieve electroweak symmetry breaking. Moreover, in an attractive region of the NMSSM parameter space, corresponding to the "alignment limit" in which one of the neutral Higgs fields lies approximately in the same direction in field space as the doublet Higgs vacuum expectation value, the observed Higgs boson is predicted to have Standard-Model-like properties. We derive analytical expressions for the alignment conditions and show that they point toward a more natural region of parameter space for electroweak symmetry breaking, while allowing for perturbativity of the theory up to the Planck scale. Moreover, the alignment limit in the NMSSM leads to a well defined spectrum in the Higgs and Higgsino sectors, and yields a rich and interesting Higgs boson phenomenology that can be tested at the LHC. We discuss the most promising channels for discovery and present several benchmark points for further study.
hep-phhep-exPRD(2016)·111 citations
12*
Cubic Ideal Ferromagnets at Low Temperature and Weak Magnetic Field
Christoph P. Hofmann🇲🇽
The low-temperature series for the free energy density, pressure, magnetization and susceptibility of cubic ideal ferromagnets in weak external magnetic fields are discussed within the effective Lagrangian framework up to three loops. The structure of the simple, body-centered, and face-centered cubic lattice is taken into account explicitly. The expansion involves integer and half-integer powers of the temperature. The corresponding coefficients depend on the magnetic field and on low-energy effective constants that can be expressed in terms of microscopic quantities. Our formulas may also serve as efficiency or consistency check for other techniques like Green's function methods, where spurious terms in the low-temperature expansion have appeared. We explore the sign and magnitude of the spin-wave interaction in the pressure, magnetization and susceptibility, and emphasize that our effective field theory approach is fully systematic and rigorous.
↳ cond-mat.str-elhep-lathep-phPhysica B(2017)·2 citations
13*
Anatomy of SU(3) flux tubes at finite temperature
Paolo Cea🇮🇹 · Leonardo Cosmai🇮🇹 · Francesca Cuteri🇮🇹 · Alessandro Papa🇮🇹
An attempt to adapt the study of color flux tubes to the case of finite temperature has been made. The field is measured both through the correlator of two Polyakov loops, one of which connected to a plaquette, and through a connected correlator of Wilson loop and plaquette in the spatial sublattice. Still the profile of the flux tube resembles the transverse field distribution around an isolated vortex in an ordinary superconductor. The temperature dependence of all the parameters characterizing the flux tube is investigated.
↳ hep-lathep-phPoS(2016)·2 citations
14*
A new recipe for $Λ$ CDM
Varun Sahni🇮🇳 · Anjan A Sen🇮🇳
It is well known that a canonical scalar field is able to describe either dark matter or dark energy but not both. We demonstrate that a non-canonical scalar field can describe both dark matter and dark energy within a unified setting. We consider the simplest extension of the canonical Lagrangian $L \propto X^{α} - V (ϕ)$ where $α \geq 1$ and $V$ is a sufficiently flat potential. In this case the kinetic term in the Lagrangian behaves just like a perfect fluid, whereas the potential term mimicks the cosmological constant. For very large values, $α ≫ 1$ , the equation of state of the kinetic term drops to zero and the expansion rate of the universe mimicks $Λ$ CDM. The velocity of sound in this model, and the associated gravitational clustering, is sensitive to the value of $α$ . For very large values of $α$ the clustering properties of our model resemble those of cold dark matter (CDM). But for smaller values of $α$ , gravitational clustering on small scales is suppressed, and our model has properties resembling those of warm dark matter (WDM). Therefore our non-canonical model has an interesting new property: while the background universe expands like $Λ$ CDM, its clustering properties can resemble those of either cold or warm dark matter.
↳ astro-ph.COgr-qchep-phhep-thEPJC(2017)·23 citations
15*
Testing the $S U (4)$ degeneracy after low-mode removal with $J = 2$ mesons
M. Denissenya🇦🇹 · L. Glozman🇦🇹 · M. Pak🇦🇹
Recent lattice results on Dirac low-mode removed $J = 1, 2$ mesons and $J = \frac{1}{2}$ baryons reveal the appearance of a new $S U (4)$ symmetry of confinement. Here the degeneracy of all $J = 2$ iso-vector states within an irreducible representation of $S U (4)$ after low-mode removal is demonstrated. The $S U (4)$ symmetry contains $S U (2)_{L} \times S U (2)_{R}$ and $U (1)_{A}$ symmetries as subgroups and mixes all compontents $u_{L}, u_{R}, d_{L}, d_{R}$ of the two-flavor Dirac field. It implies the vanishing of the interaction of quarks with the color-magnetic field, which is shown by using the QCD Hamiltonian in Coulomb gauge.
↳ hep-lathep-phnucl-thPoS(2016)·2 citations
16*
Precision measurements of the top quark couplings at the FCC
Patrick Janot🇨🇭
The design study of the Future Circular Colliders (FCC) in a 100-km ring in the Geneva area has started at CERN at the beginning of 2014, as an option for post-LHC particle accelerators. The study has an emphasis on proton-proton and electron-positron high-energy frontier machines. In the current plans, the first step of the FCC physics programme would exploit a high-luminosity e+e- collider called FCC-ee, with centre-of-mass energies ranging from below the Z pole to the t-tbar threshold and beyond, followed by 100\,TeV proton-proton collisions as ultimate goal. When combined, these two steps offer a large palette of complementary measurements and sensitivity for new physics. In particular, the association of the FCC-ee and the FCC-hh allows measurements of the top-quark electroweak and Yukawa couplings to be performed with unrivaled precision.
↳ hep-exhep-phPoS(2015)·13 citations
17*
X(3872) and Y(4140) using diquark-antidiquark operators with lattice QCD
M. Padmanath🇦🇹 · C. B. Lang🇦🇹 · S. Prelovsek🇸🇮
We discuss a recent lattice study of charmonium-like mesons with $J^{P C} = 1^{++}$ and three quark contents $c ˉ c d ˉ u$ , $c ˉ c (u ˉ u + d ˉ d)$ and $c ˉ c s ˉ s$ , where the latter two can mix with $c ˉ c$ . In this quantum channel, the long known exotic candidate, X(3872), resides. This simulation employs $N_{f} = 2$ , $m_{π} = 266$ MeV and a large basis of $c ˉ c$ , two-meson and diquark-antidiquark interpolating fields, with diquarks in both anti-triplet and sextet color representations. It aims at the possible signatures of four-quark exotic states. Along the way, we discuss the relations between the diquark-antidiquark operators and the two-meson operators via the Fierz transformations.
↳ hep-lathep-phPoS(2016)·2 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.