Fri·Sep 25, 2015Friday·September 25, 2015

1. 01*

   Spontaneous CP Violation in Lepton-sector: a common origin for ${\theta }_{13}$, Dirac CP phase and leptogenesis

   Biswajit Karmakar🇮🇳 · Arunansu Sil🇮🇳

   A possible interplay between the two terms of the general type-II seesaw formula is exercised which leads to the generation of nonzero ${\theta }_{13}$. The specific flavor structure of the model, guided by the $A_4\times Z_4\times Z_3$ symmetry and accompanied with the Standard Model singlet flavons, yields the conventional seesaw contribution to produce the tribimaximal lepton mixing which is further corrected by the presence of the $SU(2{)}_L$ triplet contribution to accommodate ${\theta }_{13}$. We consider the CP symmetry to be spontaneously broken by the complex vacuum expectation value (vev) of a singlet field $S$. While the magnitude of its complex vev is responsible for generating ${\theta }_{13}$, its phase part induces the low energy CP violating phase ($\delta$) and the CP violation required for leptogenesis. Hence the triplet contribution, although sub-dominant, plays crucial role in providing a common source for non-zero ${\theta }_{13}$, $\delta$ and CP-violation required for leptogenesis. We find that the recent hint for $\delta$ close to $3\pi /2$ is somewhat favored in this set-up though it excludes the exact equality with $3\pi /2$. We also discuss the generation of lepton asymmetry in this scenario.

   hep-phPRD(2016)·31 citations
2. 02*

   On SU(3) effective models and chiral phase-transition

   Abdel Nasser Tawfik (Egyptian Ctr. Theor. Phys., Cairo and WLCAPP, Cairo)🇪🇬 · Niseem Magdy (WLCAPP, Cairo)🇪🇬

   The sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL) model as an effective theory of quark dynamics to chiral symmetry has been utilized in studying the QCD phase-diagram. Also, Poyakov linear sigma-model (PLSM), in which information about the confining glue sector of the theory was included through Polyakov-loop potential. Furthermore, from quasi-particle model (QPM), the gluonic sector of QPM is integrated to LSM in order to reproduce recent lattice calculations. We review PLSM, QLSM, PNJL and HRG with respect to their descriptions for the chiral phase-transition. We analyse chiral order-parameter M(T), normalized net-strange condensate Delta_{q,s}(T) and chiral phase-diagram and compare the results with lattice QCD. We conclude that PLSM works perfectly in reproducing M(T) and Delta_{q,s}(T). HRG model reproduces Delta_{q,s}(T), while PNJL and QLSM seem to fail. These differences are present in QCD chiral phase-diagram. PLSM chiral boundary is located in upper band of lattice QCD calculations and agree well with freeze-out results deduced from high-energy experiments and thermal models. Also, we find that the chiral temperature calculated from from HRG model is larger than that from PLSM. This is also larger than the freeze-out temperatures calculated in lattice QCD and deduced from experiments and thermal models. The corresponding temperature T and chemical potential mu sets are very similar to that of PLSM. This might be explained, because the chiral T and mu are calculated using different order parameters; in HRG vanishing quark-antiquark condensate but in PLSM crossing (equaling) chiral condensates and Polyakov loop potentials. The latter assumed that the two phase transitions; chiral and deconfinement, take place at the same temperature.

   hep-phAdv.High Energy Phys.(2015)·5 citations
3. 03*

   Precision diboson measurements and the interplay of pT and jet-veto resummations

   Prerit Jaiswal🇺🇸 · Patrick Meade🇺🇸 · Harikrishnan Ramani🇺🇸

   In this paper we demonstrate the agreement of jet-veto resummation and pT resummation for explaining the WW cross sections at Run 1 of the LHC, and in the future. These two resummation techniques resum different logarithms, however via reweighting methods they can be compared for various differential or exclusive cross sections. We find excellent agreement between the two resummation methods for predicting the zero-jet cross section, and propose a new reweighting method for jet-veto resummation that can be used to compare other differential distributions. We advocate a cross-channel comparison for the high-luminosity run of the LHC as both a test of QCD and new physics.

   hep-phhep-exPRD(2016)·12 citations
4. 04*

   Direct probes of flavor-changing neutral currents in $e^{+}{e}^{-}$ collisions

   Alexander Khodjamirian🇩🇪 · Thomas Mannel🇩🇪 · Alexey A Petrov🇺🇸

   We propose a novel method to study flavor-changing neutral currents in the $e^{+}{e}^{-}\to D^{\ast 0}$ and $e^{+}{e}^{-}\to B_s^{\ast }$ transitions, tuning the energy of $e^{+}{e}^{-}$- collisions to the mass of the narrow vector resonance $D^{\ast 0}$ or $B_s^{\ast }$. We present a thorough study of both short-distance and long-distance contributions to $e^{+}{e}^{-}\to D^{\ast 0}$ in the Standard Model and investigate possible contributions of new physics in the charm sector. This process, albeit very rare, has clear advantages with respect to the $D^0\to e^{+}{e}^{-}$ decay: the helicity suppression is absent, and a richer set of effective operators can be probed. Implications of the same proposal for $B_s^{\ast }$ are also discussed.

   hep-phhep-exJHEP(2015)·43 citations
5. 05*

   Inclusive photoproduction of bottom quarks for low and medium pT in the general-mass variable-flavour-number scheme

   G. Kramer🇩🇪 · H. Spiesberger🇩🇪

   We present predictions for b-quark production in photoprodcution and compare with experimental data from HERA. Our theoretical predictions are obtained at next-to-leading-order in the general-mass variable-flavor-number scheme, an approach which takes into account the finite mass of the b quarks. We use realistic evolved nonperturbative fragmentation functions obtained from fits to e+e- data. We find in general good agreement of data with both the GM-VFNS and the FFNS calculations, while the more precise ZEUS data seem to prefer the GM-VFNS predictions.

   hep-phPLB(2016)·2 citations
6. 06*

   Theoretical foundations and applications of the Loop-Tree Duality in Quantum Field Theories

   Sebastian Buchta🇪🇸

   The Loop-Tree Duality (LTD) is a novel perturbative method in QFT that establishes a relation between loop-level and tree-level scattering amplitudes. This is achieved by directly applying the Residue Theorem to the loop-energy-integration. The result is a sum over all possible single cuts of the Feynman diagram in consideration integrated over a modified phase space. These single-cut integrals, called Dual contributions, are in fact tree-level objects and thus give rise to the opportunity of bringing loop- and tree-contributions together, treating them simultaneously in a common Monte Carlo event generator. Initially introduced for one-loop scalar integrals, the applicability of the LTD has been expanded ever since. In this thesis, we show how to deal with Feynman graphs beyond simple poles by taking advantage of Integration By Parts (IBP) relations. Furthermore, we investigate the cancellation of singularities among Dual contributions as well as between real and virtual corrections. For the first time, a numerical implementation of the LTD was done in the form of a computer program that calculates one-loop scattering diagrams. We present details on the contour deformation employed alongside the results for scalar integrals up to the pentagon- and tensor integrals up to the hexagon-level.

   hep-ph30 citations
7. 07*

   Collider searches for non-perturbative low-scale gravity states

   Douglas M. Gingrich🇨🇦

   The possibility of producing non-perturbative low-scale gravity states in collider experiments was first discussed in about 1998. The ATLAS and CMS experiments have searched for non-perturbative low-scale gravity states using the Large Hadron Collider (LHC) with a proton--proton centre of mass energy of 8 TeV. These experiments have now seriously confronted the possibility of producing non-perturbative low-scale gravity states which were proposed over 17 years ago. I will summarise the results of the searches, give a personal view of what they mean, and make some predictions for 13 TeV centre of mass energy. I will also discuss early ATLAS 13 TeV centre of mass energy results.

   hep-phgr-qchep-exhep-thInt.J.Mod.Phys.A(2015)·4 citations
8. 08*

   Heavy Quarkonium in a Holographic Basis

   Yang Li🇺🇸 · Pieter Maris🇺🇸 · Xingbo Zhao🇺🇸 · James P. Vary🇺🇸

   We study the heavy quarkonium within the basis light-front quantization approach. We implement the one-gluon exchange interaction and a confining potential inspired by light-front holography. We adopt the holographic light-front wavefunction (LFWF) as our basis function and solve the non-perturbative dynamics by diagonalizing the Hamiltonian matrix. We obtain the mass spectrum for charmonium and bottomonium. With the obtained LFWFs, we also compute the decay constants and the charge form factors for selected eigenstates. The results are compared with the experimental measurements and with other established methods.

   hep-phnucl-thPLB(2016)·173 citations
9. 09*

   How to avoid unnatural hierarchical thermal leptogenesis

   Jackson D. Clarke🇦🇺

   A one-flavour naturalness argument suggests that the Type I seesaw model cannot naturally explain neutrino masses and the baryon asymmetry of the Universe via hierarchical thermal leptogenesis. We prove that there is no way to avoid this conclusion in a minimal three-flavour setup. We then comment on the simplest ways out. In particular, we focus on a resolution utilising a second Higgs doublet. Such models predict an automatically SM-like Higgs boson, (maximally) TeV-scale scalar states, and low- to intermediate-scale hierarchical leptogenesis with $10^3\text{ GeV}\lesssim M_{N_1}\lesssim 10^7\text{ GeV}$.

   hep-phPoS(2015)·2 citations
10. 10*

    $\nu$DFSZ: a technically natural non-supersymmetric model of neutrino masses, baryogenesis, the strong CP problem, and dark matter

    Jackson D. Clarke🇦🇺 · Raymond R. Volkas🇦🇺

    We describe a minimal extension of the standard model by three right-handed neutrinos, a scalar doublet, and a scalar singlet (the "$\nu$DFSZ") which serves as an existence proof that weakly coupled high-scale physics can naturally explain phenomenological shortcomings of the SM. The $\nu$DFSZ can explain neutrino masses, baryogenesis, the strong CP problem, and dark matter, and remains calculably natural despite a hierarchy of scales up to $\sim 10^{11}$ GeV. It predicts a SM-like Higgs boson, (maximally) TeV-scale scalar states, intermediate-scale hierarchical leptogenesis ($10^5\text{ GeV}\lesssim M_N\lesssim 10^7\text{ GeV}$), and axionic dark matter.

    hep-phPRD(2016)·59 citations
11. 11*

    Towards the understanding of jet shapes and cross sections in heavy ion collisions using soft-collinear effective theory

    Yang-Ting Chien🇺🇸 · Ivan Vitev🇺🇸

    We calculate the jet shape and the jet cross section in heavy ion collisions using soft-collinear effective theory (SCET) and its extension with Glauber gluon interactions in the medium (SCET${}_{\mathrm{G}}$). We use the previously developed framework to systematically resum the jet shape at next-to-leading logarithmic accuracy, and we consistently include the medium modification by incorporating the leading order medium-induced splitting functions. The calculation provides, for the first time, a quantitative understanding of the jet shape modification measurement in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV at the LHC. The inclusive jet suppression is also calculated within the same framework beyond the traditional concept of parton energy loss, and the dependence on the centrality, the jet radius and the jet kinematics is examined. In the end we present predictions for the anticipated jet shape and cross section measurements in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}\approx 5.1$ TeV at the LHC.

    hep-phhep-exnucl-exnucl-thJHEP(2016)·150 citations
12. 12*

    Optimal-observable analysis of possible new physics in $B\to D^{(\ast )}\tau {\nu }_{\tau }$

    Srimoy Bhattacharya🇮🇳 · Soumitra Nandi🇮🇳 · Sunando Kumar Patra🇮🇳

    We study all possible observables in $B\to D^{(\ast )}\tau {\nu }_{\tau }$ with new physics (NP), including new vector, scalar and tensor interactions, and investigate the prospects of extracting NP Wilson coefficients with optimal observables. Analysis of the full $q^2$ integrated branching fractions of $B\to D^{(\ast )}\tau {\nu }_{\tau }$ show that the overall sensitivity of the observables of $B\to D\tau {\nu }_{\tau }$ is more towards the scalar current, whereas the bin-by-bin analysis of $q^2$ distribution of the differential branching fraction points to regions of $q^2$ sensitive to tensor interactions. Interestingly, the observables in $B\to D^{\ast }\tau {\nu }_{\tau }$ are more sensitive to tensor interactions, and bin-by-bin analysis of this mode shows the distinct regions of $q^2$ sensitive to vector or scalar interactions. In addition to that, the $\tau$ polarisation asymmetry is found to be more sensitive to NP compared to the other observables, in both decay modes.

    hep-phhep-exPRD(2016)·82 citations
13. 13*

    Factorization of the dijet cross section with the Georgi jet algorithm in $e^{+}{e}^{-}$ annihilation

    Junegone Chay🇰🇷 · Inchol Kim🇰🇷

    We consider the dijet cross section in $e^{+}{e}^{-}$ annihilation using the Georgi jet algorithm, or the maximizing jet algorithm. The cross section is factorized into the hard, collinear and soft parts. Each factorized function is computed to next-to-leading order, and is shown to be infrared finite. The large logarithms are resummed at next-to-leading logarithmic accuracy. By analyzing the phase space for the jet algorithm, the Georgi algorithm turns out to be equivalent to the Sterman-Weinberg and the cone-type algorithms.

    hep-ph0 citations
14. 14*

    Spontaneous violation of mirror symmetry

    Igor T. Dyatlov🇷🇺

    A symmetry violation model is considered for a system that can spontaneously choose between identical states which differ from each other only in weak properties (R-L). Such mirror symmetry allows reproduction of observed qualitative properties of quark and lepton mixing matrices. The lepton mixing matrix evidences in this case in favor of the inverse mass spectrum and the Dirac nature of SM neutrino. Notwithstanding the Dirac properties of neutrino, an exchange of lepton numbers such as $e^{-}+{\mu }^{+}\to e^{+}+{\mu }^{-}$ is possible but with only leptons participating in the process.

    hep-phPhys.Atom.Nucl.(2015)·6 citations
15. 15*

    NMSSM interpretations of the observed Higgs signal

    Florian Domingo🇩🇪 · Georg Weiglein (DESY)🇩🇪

    While the properties of the signal that was discovered in the Higgs searches at the LHC are consistent so far with the Higgs boson of the Standard Model (SM), it is crucial to investigate to what extent other interpretations that may correspond to very different underlying physics are compatible with the current results. We use the Next-to-Minimal Supersymmetric Standard Model (NMSSM) as a well-motivated theoretical framework with a sufficiently rich Higgs phenomenology to address this question, making use of the public tools HiggsBounds and HiggsSignals in order to take into account comprehensive experimental information on both the observed signal and on the existing limits from Higgs searches at LEP, the TeVatron and the LHC. We find that besides the decoupling limit resulting in a single light state with SM-like properties, several other configurations involving states lighter or quasi-degenerate with the one at about 125 GeV turn out to give a competitive fit to the Higgs data and other existing constraints. We discuss the phenomenology and possible future experimental tests of those scenarios, and compare the features of specific scenarios chosen as examples with those arising from a more global fit.

    hep-phJHEP(2016)·33 citations
16. 16*

    Violations of discrete space-time symmetries in chiral effective field theory

    J. de Vries🇩🇪 · Ulf-G. Meißner🇩🇪

    We review recent progress in the theoretical description of the violation of discrete space-time symmetries in hadronic and nuclear systems. We focus on parity-violating and time-reversal-conserving interactions which are induced by the Standard Model weak interaction, and on parity- and time-reversal-violating interactions which can be caused by a nonzero QCD theta term or by beyond-the-Standard Model physics. We discuss the origins of such interactions and review the development of the chiral effective field theory extension that includes discrete symmetry violations. We discuss the construction of symmetry-violating chiral Lagrangians and nucleon-nucleon potentials and their applications in few-body systems.

    hep-phnucl-exnucl-thIJMPE(2016)·52 citations
17. 17*

    Summary and Outlook: 2015 Lepton-Photon Symposium

    John Ellis🇬🇧

    What life is there after Higgs? Specifically, what physics lies beyond the Standard Model (SM)? These are the biggest questions in particle physics today, and my talk is oriented towards efforts to answer them at the LHC and elsewhere.

    hep-phhep-exhep-thPoS(2016)·5 citations
18. 18*

    Quarkonium at finite temperature: Towards realistic phenomenology from first principles

    Yannis Burnier🇨🇭 · Olaf Kaczmarek🇩🇪 · Alexander Rothkopf🇩🇪

    We present the finite temperature spectra of both bottomonium and charmonium, obtained from a consistent lattice QCD based potential picture. Starting point is the complex in-medium potential extracted on full QCD lattices with dynamical u,d and s quarks, generated by the HotQCD collaboration. Using the generalized Gauss law approach, vetted in a previous study on quenched QCD, we fit $\mathrm{Re}[V]$ with a single temperature dependent parameter $m_D$, the Debye screening mass, and confirm the up to now tentative values of $\mathrm{Im}[V]$. The obtained analytic expression for the complex potential allows us to compute quarkonium spectral functions by solving an appropriate Schrödinger equation. These spectra exhibit thermal widths, which are free from the resolution artifacts that plague direct reconstructions from Euclidean correlators using Bayesian methods. In the present adiabatic setting, we find clear evidence for sequential melting and derive melting temperatures for the different bound states. Quarkonium is gradually weakened by both screening ($\mathrm{Re}[V]$) and scattering ($\mathrm{Im}[V]$) effects that in combination lead to a shift of their in-medium spectral features to smaller frequencies, contrary to the mass gain of elementary particles at finite temperature.

    hep-phhep-latnucl-thJHEP(2015)·137 citations
19. 19*

    ${\chi }_{cJ}\to e^{+}{e}^{-}$ decays revisited

    N. Kivel🇩🇪 · M. Vanderhaeghen🇩🇪

    We present a calculation of the width for ${\chi }_{cJ}\to e^{+}{e}^{-}$ decay. The amplitude of the process is computed within the NRQCD framework. The leading-order contribution is described by two terms associated with the two different integration domains in the electromagnetic loop describing two-photon annihilation of the heavy quark-antiquark pair. The corresponding operators are defined in the framework of NRQCD. The matrix element of one of these operators describes a configuration with an ultrasoft photon and can be associated with the higher Fock state of the heavy meson. In order to compute this contribution we use the heavy hadron chiral perturbation theory. We obtain that this contribution is numerically dominant. The obtained estimates for the decay widths of the ${\chi }_{c1}$ and ${\chi }_{c2}$ states are $0.09$ eV and $0.06$ eV, respectively.

    hep-phJHEP(2016)·22 citations
20. 20*

    Towards a Numerical Implementation of the Loop-Tree Duality Method

    Sebastian Buchta🇪🇸 · Grigorios Chachamis🇪🇸 · Petros Draggiotis🇬🇷 · Ioannis Malamos🇪🇸 · German Rodrigo🇪🇸

    We review the recent progress on the numerical implementation of the Loop-Tree Duality Method (LTDM) for the calculation of scattering amplitudes. A central point is the analysis of the singularities of the integrand. In the framework of the LTDM some of these singularities cancel out. The ones left over are dealt with by contour deformation. We present details on how to achieve this as well as first results.

    hep-phNucl.Part.Phys.Proc.(2015)·13 citations
21. 21*

    Leading logarithms for mesons and nucleons

    Johan Bijnens (Lund)🇸🇪 · Karol Kampf (Prague)🇨🇿 · Alexey Vladimirov (Regensburg)🇩🇪

    This talk describes the work done in calculating leading logarithms in massive effective field theories. We discuss shortly leading logarithms in renormalizable theories and how they can be calculated using only one-loop calculations in effective field theories. The remainder of the talk discusses masses, decay constants, condensates and anomalous processes in mesonic effective field theories like Chiral Perturbation Theory and the expansion of the nucleon mass.

    hep-phPoS(2016)·1 citation
22. 22*

    Cutoff Regularization Method in Gauge Theories

    G. Cynolter🇭🇺 · E. Lendvai🇭🇺

    A Lorentz and gauge symmetry preserving regularization method is discussed in four dimension based on momentum cutoff. We use the conditions of gauge invariance or equivalently the freedom of shift of the loop momentum to define the evaluation of the terms carrying even number of Lorentz indices, e.g. proportional to $k_{\mu }{k}_{\nu }$. The remaining scalar integrals are calculated with a four dimensional momentum cutoff. The finite terms (independent of the cutoff) are free of ambiguities coming from subtractions in non-trivial cases. Finite parts of the result are equal with the results of dimensional regularization. The proposed method can be applied to various physical processes where the use of dimensional regularization is subtle or a physical cutoff is present. As a famous example it is shown that the triangle anomaly can be calculated unambiguously with this new improved cutoff.

    hep-ph17 citations
23. 23*

    Leptoquark explanation of $h\to \mu \tau$ and muon $(g-2)$

    Seungwon Baek🇰🇷 · Kenji Nishiwaki🇰🇷

    We consider lepton flavor violating Higgs decay, specifically $h\to \mu \tau$, in a leptoquark model. We introduce two scalar leptoquarks with the $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y$ quantum numbers, $(3,2,7/6)$ and $(3,2,1/6)$, which do not generate the proton decay within renormalizable level. They can mix with each other by interactions with the standard model Higgs. The constraint from the charged lepton flavor violating process, ${\tau }^{-}\to {\mu }^{-}\gamma$, is very strong when only one leptoquark contribution is considered. However, we demonstrate that significant cancellation is possible between the two leptoquark contributions. We show that we can explain the CMS (ATLAS) excess in $h\to \mu \tau$. We also show that muon $(g-2)$ anomaly can also be accommodated.

    hep-phPRD(2016)·65 citations
24. 24*

    On the tensor-to-scalar ratio in large single-field inflation models

    Gabriela Barenboim🇪🇸 · Wan-Il Park🇪🇸

    We show that generically the tensor-to-scalar ratio in large single-field inflation scenarios is bounded to be larger than $\mathcal{O}(10^{-3})$ for the spectral index in the range favored by observations.

    ↳ astro-ph.COhep-ph6 citations
25. 25*

    Double scattering production of two ${\rho }^0$ mesons in UPC

    Mariola Kłusek-Gawenda🇵🇱 · Antoni Szczurek🇵🇱

    We review our recent results for double-scattering mechanism in the exclusive $AA\to AA{\rho }^0{\rho }^0$ reaction in ultrarelativistic ultraperipheral heavy ion collisions. The cross section for single and double-${\rho }^0$ production is calculated in the impact parameter space equivalent photon approximation. We compare the results of our calculation with the STAR and ALICE Collaboration results on one ${\rho }^0(770)$ meson and four-charged-pion production.

    ↳ nucl-thhep-phActa Phys.Polon.Supp.(2015)·0 citations
26. 26*

    Estimating $\eta /s$ of QCD matter at high baryon densities

    Iu. Karpenko🇺🇦 · M. Bleicher🇩🇪 · P. Huovinen🇩🇪 · H. Petersen🇩🇪

    We report on the application of a cascade + viscous hydro + cascade model for heavy ion collisions in the RHIC Beam Energy Scan range, $\sqrt{s_{\mathrm{NN}}}=6.3\dots 200$ GeV. By constraining model parameters to reproduce the data we find that the effective(average) value of the shear viscosity over entropy density ratio $\eta /s$ decreases from 0.2 to 0.08 when collision energy grows from $\sqrt{s_{\mathrm{NN}}}\approx 7$ to 39 GeV.

    ↳ nucl-thhep-phJ.Phys.Conf.Ser.(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.