Tue·Jan 19, 2016Tuesday·January 19, 2016

1. 01*

   NLO efforts in Herwig++

   Christian Reuschle🇺🇸 · Johannes Bellm🇬🇧 · Stefan Gieseke🇩🇪 · David Grellscheid🇬🇧 · Simon Plätzer🇬🇧 · Michael Rauch🇩🇪 · Peter Richardson🇬🇧 · Peter Schichtel🇬🇧 · Michael H. Seymour🇬🇧 · Andrzej Siodmok🇨🇭 · Alexandra Wilcock🇬🇧 · Nadine Fischer🇩🇪 and 4 other authors

   With the advent and recent extension of the BLHA standard to interface Monte Carlo event generators and one-loop matrix element providers, the Herwig++ event generator has expanded its range of applicability to a multitude of underlying hard processes at NLO QCD. The new NLO development is centered around the Matchbox framework, which turns fixed NLO QCD calculations into parton shower matched calculations - to be matched to the two parton shower variants of Herwig++. Matchbox provides thereby for the automated setup of the underlying fixed NLO QCD calculations and the interface to the one-loop matrix element providers, as well as for an efficient and automated multi-channel phase space sampling, and forms the basis for the NLO capabilities of the new release of Herwig++. Along with several other new features and developments, the new release marks the end of distinguishing Herwig++ and (Fortran) HERWIG, and constitutes the first major release of version 7 of the Herwig event generator.

   hep-phPoS(2016)·3 citations
2. 02*

   Analytic approaches to relativistic hydrodynamics

   Yoshitaka Hatta🇯🇵

   I summarize our recent work towards finding and utilizing analytic solutions of relativistic hydrodynamic. In the first part I discuss various exact solutions of the second-order conformal hydrodynamics. In the second part I compute flow harmonics $v_n$ analytically using the anisotropically deformed Gubser flow and discuss its dependence on $n$, $p_T$, viscosity, the chemical potential and the charge.

   hep-phnucl-exnucl-thNPA(2016)·4 citations
3. 03*

   Insight into $f_0(980)$ through the $B_{(s)}$ charmed decays

   Zhi-Qing Zhang🇨🇳 · Si-Yang Wang🇨🇳 · Xing-Ke Ma🇨🇳

   Through analyzing the $B_{(s)}$ charmed decays $B^0\to {\bar{D}}_0{f}_0(980)$ and $B_s\to {\bar{D}}_0{f}_0(980)$ within the framework of the PQCD factorization approach and comparing with the current data, we find that there are two possible regions for the $f_0(980)-f_0(500)$ mixing angle $\theta$: one is centered at $34^{\circ }\sim 38^{\circ }$ and the other is falls into $142^{\circ }\sim 154^{\circ }$. The former can overlap mostly with one of allowed angle regions extracted from the decay $B^0\to {\bar{D}}_0{f}_0(500)$. The branching fractions of $B_s$ decay modes are less sensitive to the mixing angle compared with those of B decay modes. Especially, for the decay $B_s\to D^0{f}_0(980)$, its branching fraction changes only slightly between $(1.2\sim 1.8)\times 10^{-7}$ when the mixing angle $\theta$ runs from $0^{\circ }$ to $180^{\circ }$. All of our results support the picture that the $f_0(980)$ is dominated by two quark component in the B decay dynamic mechanism. Furthermore, the $s\bar{s}$ component is more important than the $q\bar{q}=(u\bar{u}+d\bar{d})/\sqrt{2}$ component. This point is different from $f_0(500)/\sigma$. Last but not least, our picture is not in conflict with the popular four-quark explanation.

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

   Test of the triple Higgs boson form factor in ${\mu }^{-}{\mu }^{+}\to HH$

   G.J. Gounaris🇬🇷 · F.M. Renard🇫🇷

   We study the sensitivity of the process ${\mu }^{-}{\mu }^{+}\to HH$ to the $q^2$-dependence of the $HHH$ form factor, which can reflect the Higgs boson structure, especially in the case of compositeness. We compute the Born and 1 loop SM contribution to this process. We then show how the ${\mu }^{-}{\mu }^{+}\to HH$ polarized and unpolarized cross sections are modified by the presence of various types of anomalous contributions to the $HHH$ form factor, in particular Higgs constituents in the case of compositeness.

   hep-phPRD(2016)·6 citations
5. 05*

   Towards a microscopic understanding of nucleon polarizabilities

   Gernot Eichmann🇩🇪

   We outline a microscopic framework to calculate nucleon Compton scattering from the level of quarks and gluons within the covariant Faddeev approach. We explain the connection with hadronic expansions of the Compton scattering amplitude and discuss the obstacles in maintaining electromagnetic gauge invariance. Finally we give preliminary results for the nucleon polarizabilities.

   hep-phnucl-thFew Body Syst.(2016)·4 citations
6. 06*

   A Detailed Analysis of Flavour-changing Decays of Top Quarks as a Probe of New Physics at the LHC

   Debjyoti Bardhan🇮🇳 · Gautam Bhattacharyya🇮🇳 · Diptimoy Ghosh🇮🇱 · Monalisa Patra🇭🇷 · Sreerup Raychaudhuri🇮🇳

   If the LHC should fail to observe direct signals for new physics, it may become necessary to look for new physics effects in rare events such as flavour-changing decays of the top quark, which, in the Standard Model, are predicted to be too small to be observed. We set up the theoretical framework in which experimentally accessible results can be expected in models of new physics, and go on to discuss two models of supersymmetry -- one with conserved $R$-parity, and one without $R$-parity -- to illustrate how the flavour-changing signals are predicted in these models. In the latter case, there is a distinct possibility of detecting the rare decay $t\to c+Z^0$ at the LHC. We also present a detailed set of very general formulae which can be used to make similar calculations in diverse models of new physics.

   hep-phPRD(2016)·25 citations
7. 07*

   Extracting the QCD ${\Lambda }_{\overline{MS}}$ parameter in Drell-Yan Process using Collins-Sopper-Sterman approach

   R. Taghavi🇮🇷 · A. Mirjalili🇮🇷

   In this work we directly fit the QCD dimensional transmutation parameter, ${\Lambda }_{\overline{MS}}$, to experimental data of Drell-Yan (DY) observables. For this purpose we first obtain the evolution of transverse momentum dependent parton distribution functions (TMDPDFs) up to the NNLO approximation based on Collins-Sopper-Sterman formalism. As is expecting the TMDPDFs are appearing at larger values of transvers momentum by increasing the energy scales and also the order of approximation. Then we calculate the cross section related to the TMDPDFs in the DY process. As a consequence of fitting to the E288 experimental data at center of mass energy $\sqrt{s}=23.8$ $GeV$, we obtain ${\Lambda }_{\overline{MS}}=249\pm 7MeV$ corresponding to the renormalized coupling constant ${\alpha }_s(M_z^2)=0.119\pm 0.001$ which is within the acceptable range for this quantity. The results for DY cross section at different energy scales are in good agreement within the available data.

   hep-phMod.Phys.Lett.A(2017)·5 citations
8. 08*

   Sensitivities to PDFs in parton shower MC generator reweighting and tuning

   Andy Buckley🇬🇧

   Evaluating parton density systematic uncertainties in Monte~Carlo event generator predictions has long been achieved by reweighting between the original and systematic PDFs for the initial state configurations of the individual simulated events. This weighting is now pre-emptively performed in many generators, providing convenient weight factors for PDF and scale systematics -- including for NLO calculations where counterterms make the weight calculation complex. This note attempts a pedagogical discussion and empirical study of the consequences of neglecting the effects of PDF variations on the beyond-fixed-order components of MC models, and the implications for parton shower & MPI tuning strategies. We confirm that the effects are usually small, for well-understood reasons, and discuss the connected issue of consistent treatment of the strong coupling between PDFs and parton showers, where motivations from physical principles and the need for good data-description are not always well-aligned.

   hep-ph4 citations
9. 09*

   Test Flavor SU(3) symmetry in Exclusive ${\Lambda }_c$ decays

   Cai-Dian Lü🇨🇳 · Wei Wang🇨🇳 · Fu-Sheng Yu🇨🇳

   Flavor SU(3) symmetry is a powerful tool to analyze charmed baryon decays, however its applicability remains to be experimentally validated. Since there is not much data on ${\Xi }_c$ decays, various exclusive ${\Lambda }_c$ decays especially the ones into a neutron state are essential for the test of flavor symmetry. These decay modes are also helpful to investigate final state interactions in charmed baryon decays. In this work, we discuss the explicit roles of ${\Lambda }_c$ decays into a neutron in testing the flavor symmetry and exploring final state interactions. The involved decay modes include semileptonic decays, two-body and three-body non-leptonic decays, but all of them have not been experimentally observed to date.

   hep-phhep-exPRD(2016)·158 citations
10. 10*

    On the anomalous mass defect of strange stars in the Field Correlator Method

    F. I. M. Pereira🇧🇷

    We investigate general aspects of the mass defects of strange stars in the context of the Field Correlator Method, without magnetic field. The main parameters of the model that enter the corresponding nonperturbative equation of state of the quark gluon plasma are the gluon condensate $G_2$ and the large distance static $Q\bar{Q}$ potential $V_1$. We calculate mass defects of stellar configurations in the central density range $11<\log {\rho }_c<18$. In general, the mass defects are strongly dependent on the model parameters. For a large range of values of $G_2$ and $V_1$, we obtain anomalous mass defects with magnitudes around $10^{53}$erg\,, of the same order of the observed energies of gamma-ray bursts and neutrino emissions in SN1987A, and of the theoretically predicted energies of the quark-novae explosions.

    hep-phastro-ph.HENPA(2016)·1 citation
11. 11*

    The $s$-channel Charged Higgs in the Fully Hadronic Final State at LHC

    Ijaz Ahmed · Majid Hashemi

    With the current measurements performed by CMS and ATLAS experiments, the light charged Higgs scenario ($m_{H^{\pm }}$ $<$ 160 GeV), is excluded for most of the parameter space in the context of MSSM. However, there is still possibility to look for heavy charged Higgs boson particularly in the $s$-channel single top production process where the charged Higgs may appear as a heavy resonance state and decay to $t\bar{b}$. The production process under consideration in this paper is $pp\text{ra}{H}^{\pm }\text{ra}t\bar{b}+h.c.$, where the top quark decays to $W^{+}b$ and $W^{+}$ boson subsequently decays to two light jets. It is shown that despite the presence of large QCD and electroweak background events, the charged Higgs signal can be extracted and observed at a large area of MSSM parameter space ($m_{H^{\pm }}$,tan$\beta$) at LHC. The observability of charged Higgs is potentially demonstrated with 5$\sigma$ contours and $95\%$ confidence level exclusion curves at different integrated LHC luminosities assuming a nominal center of mass energy of $\sqrt{s}$ = 14 TeV.

    hep-phEPJC(2016)·3 citations
12. 12*

    On Electroweak Phase Transition and Di-photon Excess with a 750 GeV Scalar Resonance

    Anish Ghoshal🇮🇳

    For successful electroweak baryogenesis to take place through the sphaleron process the universe needs to undergo a strong first order cosmological phase transition. While it does not occur in the Standard Model it becomes possible in the presence of extra scalars in BSM. One of these scalars can well be responsible for the recently observed diphoton excess in the CMS and ATLAS experiments in LHC. We study the Electroweak phase transition in a myriad of scalar models in this context.

    hep-ph28 citations
13. 13*

    Dark Radiative Inverse Seesaw Mechanism

    Amine Ahriche🇮🇹 · Sofiane M. Boucenna🇮🇹 · Salah Nasri🇦🇪

    We present a minimal model that simultaneously accounts for neutrino masses and the origin of dark matter (DM) and where the electroweak phase transition is strong enough to allow for electroweak baryogenesis. The Standard Model is enlarged with a Majorana fermion, three generations of chiral fermion pairs, and a single complex scalar that plays a central role in DM production and phenomenology, neutrino masses, and the strength of the phase transition. All the new fields are singlets under the SM gauge group. Neutrino masses are generated via a new variant of radiative inverse seesaw where the required small mass term is generated via loops involving DM and no large hierarchy is assumed among the mass scales. The model offers all the advantage of low-scale neutrino mass models as well as a viable dark matter candidate that is testable with direct detection experiments.

    hep-phPRD(2016)·43 citations
14. 14*

    Probing Radiative Neutrino Mass Models with Dilepton Events at the LHC

    Chahrazed Guella🇩🇿 · Dounia Cherigui🇩🇿 · Amine Ahriche🇮🇹 · Salah Nasri🇦🇪 · Rachik Soualah🇮🇹

    In this work, we investigate the possibility of probing a class of neutrino mass models at the LHC proton-proton collisions with 8 and 14 TeV energies. The existence of lepton flavor violating interactions for a singlet charged scalar, $S^{\pm }$, that couples to the leptons could induce many processes such as $pp\to {\ell }_{\alpha }^{\pm }{\ell }_{\beta }^{\mp }+\text{slashed}E$. Using the processes with ${\ell }_{\alpha }{\ell }_{\beta }=ee,e\mu ,\mu \mu$, we found that an inclusive cut on the $M_{T2}$ event variable is vital in our analysis and leads to an effective suppression of the large Standard Model background. Our results show possible detectability of the charged scalars effect, especially at the $\sqrt{s}=14\text{TeV}$.

    hep-phPRD(2016)·20 citations
15. 15*

    Scalar dark matter in an extra dimension inspired model

    Roberto Lineros🇪🇸 · Fabio Pereira dos Santos🇧🇷

    In this work we consider a singlet scalar propagating in a flat large extra dimension. The first Kaluza-Klein mode associated to this singlet scalar will be a viable dark matter candidate. The tower of new particles enriches the calculation of the relic density due effect of coannihilation. For large mass splitting, the model converges to the predictions of the singlet dark matter model. For nearly degenerate mass spectrum, coannihilations increase the cross sections used for direct and indirect dark matter searches. We investigate the impact of the Kaluza-Klein tower associated to singlet scalar for indirect and direct detection of dark matter.

    hep-phastro-ph.COJ.Phys.Conf.Ser.(2016)·0 citations
16. 16*

    Gauge dependence on the chiral phase transition of QCD at finite temperature in the Schwinger-Dyson equation

    Hiroaki Kohyama🇹🇼

    We study the gauge dependence on the chiral phase transition of Quantum chromodynamics at finite temperature based on the quenched Schwinger-Dyson equation. We first solve the equations without approximations at finite temperature in general gauge, then study the gauge dependence on the critical temperature of the chiral phase transition. We find that the critical temperature drastically depends on the choice of the gauge, and the parameters at the quenched level in the Schwinger-Dyson equations.

    hep-ph0 citations
17. 17*

    Midrapidity inclusive densities in high energy $pp$ collisions in additive quark model

    Yu.M. Shabelski🇷🇺 · A.G. Shuvaev🇷🇺

    High energy (CERN SPS and LHC) inelastic $pp$ ($p\bar{p}$) scattering is treated in the framework of additive quark model together with Pomeron exchange theory. We extract the midrapidity inclusive density of the charged secondaries produced in a single quark-quark collision and investigate its energy dependence. Predictions for the $\pi p$ collisions are presented.

    hep-phEPJC(2016)·4 citations
18. 18*

    Occam's Razor in Quark Mass Matrices

    Morimitsu Tanimoto🇯🇵 · Tsutomu T. Yanagida🇯🇵

    On the standpoint of Occam's Razor approach, we consider the minimum number of parameters in the quark mass matrices needed for the successful CKM mixing and CP violation. We impose three zeros in the down-quark mass matrix with taking the diagonal up-quark mass matrix to reduce the number of free parameters. The three zeros are maximal zeros in order to have a CP violating phase in the quark mass matrix. Then, there remain six real parameters and one CP violating phase, which is the minimal number to reproduce the observed data of the down-quark masses and the CKM parameters. The twenty textures with three zeros are examined. Among them, the thirteen textures are viable for the down-quark mass matrix. As a representative of these textures, we discuss a texture $M_d^{(1)}$ in details. By using the experimental data on $\sin 2\beta$, ${\theta }_{13}$ and ${\theta }_{23}$ together with the observed quark masses, the Cabibbo angle is predicted to be close to the experimental data. It is found that this surprising result remains unchanged in all other viable textures. We also investigate the correlations among $|V_{ub}/V_{cb}|$, $\sin 2\beta$ and $J_{CP}$. For all textures, the maximal value of the ratio $|V_{ub}/V_{cb}|$ is $0.09$, which is smaller than the upper-bound of the experimental data, $0.094$. We hope that this prediction will be tested in future experiments.

    hep-phPTEP(2016)·19 citations
19. 19*

    The evolution of ${\sigma }^{\gamma P}$ with coherence length

    Allen Caldwell🇩🇪

    Assuming the form ${\sigma }^{\gamma P}\propto l^{{\lambda }_{\mathrm{eff}}}$ at fixed $Q^2$ for the behavior of the virtual-photon proton scattering cross section, where $l$ is the coherence length of the photon fluctuations, it is seen that the extrapolated values of ${\sigma }^{\gamma P}$ for different $Q^2$ cross for $l\approx 10^8$~fm. It is argued that this behavior is not physical, and that the behavior of the cross sections must change before this coherence length $l$ is reached. This could set the scale for the onset of saturation of parton densities.

    hep-phNew J.Phys.(2016)·7 citations
20. 20*

    A four-loop Radiative Seesaw Model

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼

    We propose a new type of radiative neutrino model with global hidden $U(1)$ symmetry, in which neutrino masses are induced at the four loop level. Then we discuss the muon anomalous magnetic moment to solve the discrepancy between observation and the standard model prediction, and estimate the relic density of a fermion or boson DM candidate in the model. We also discuss the diphoton resonance $R$ by considering a process $pp\to R\to \gamma \gamma$ as a possible signal of our model.

    hep-phPLB(2017)·60 citations
21. 21*

    Central exclusive diffractive production of ${\pi }^{+}{\pi }^{-}$ continuum, scalar and tensor resonances in $pp$ and $p\bar{p}$ scattering within tensor pomeron approach

    Piotr Lebiedowicz🇵🇱 · Otto Nachtmann🇩🇪 · Antoni Szczurek🇵🇱

    We consider central exclusive diffractive dipion production in the reactions $pp\to pp{\pi }^{+}{\pi }^{-}$ and $p\bar{p}\to p\bar{p}{\pi }^{+}{\pi }^{-}$ at high energies. We include the dipion continuum, the dominant scalar $f_0(500)$, $f_0(980)$, and tensor $f_2(1270)$ resonances decaying into the ${\pi }^{+}{\pi }^{-}$ pairs. The calculation is based on a tensor pomeron model and the amplitudes for the processes are formulated in terms of vertices respecting the standard crossing and charge-conjugation relations of Quantum Field Theory. The formulae for the dipion continuum and tensor meson production are given here for the first time. The theoretical results are compared with existing STAR, CDF, CMS experimental data and predictions for planned or being carried out experiments (ALICE, ATLAS) are presented. We show the influence of the experimental cuts on the integrated cross section and on various differential distributions for outgoing particles. Distributions in rapidities and transverse momenta of outgoing protons and pions as well as correlations in azimuthal angle between them are presented. We find that the relative contribution of resonant $f_2(1270)$ and dipion continuum strongly depends on the cut on proton transverse momenta or four-momentum transfer squared $t_{1,2}$ which may explain some controversial observations made by different ISR experiments in the past. The cuts may play then the role of a $\pi \pi$ resonance filter. We suggest some experimental analyses to fix model parameters related to the pomeron-pomeron-$f_2$ coupling.

    hep-phhep-exPRD(2016)·71 citations
22. 22*

    Hierarchical vs Degenerate 2HDM: The LHC Run 1 Legacy at the Onset of Run 2

    G. C. Dorsch🇩🇪 · S. J. Huber🇬🇧 · K. Mimasu🇬🇧 · J. M. No🇬🇧

    Current discussions of the allowed two-Higgs-doublet model (2HDM) parameter space after LHC Run 1 and the prospects for Run 2 are commonly phrased in the context of a quasi-degenerate spectrum for the new scalars. Here we discuss the generic situation of a 2HDM with a non-degenerate spectrum for the new scalars. This is highly motivated from a cosmological perspective since it naturally leads to a strongly first order electroweak phase transition that could explain the matter-antimatter asymmetry in the Universe. While constraints from measurements of Higgs signal strengths do not change, those from searches of new scalar states get modified dramatically once a non-degenerate spectrum is considered.

    hep-phPRD(2016)·66 citations
23. 23*

    NNLO QCD corrections for Z boson plus jet production

    A. Gehrmann-De Ridder🇨🇭 · T. Gehrmann🇨🇭 · E.W.N. Glover🇬🇧 · A. Huss🇨🇭 · T.A. Morgan🇬🇧

    We discuss the next-to-next-to-leading order (NNLO) QCD corrections to Z boson production in association with a jet including all partonic channels at all color levels and including the leptonic decay of the Z boson. We focus on the optimization of the numerical evaluation of the double-real contribution and demonstrate that our procedure for spreading the Monte Carlo integration over $\mathcal{O}(1000)$ cores and recombining the results afterwards lead to stable results with sensible error estimates. We apply representative cuts on the jet and charged lepton transverse momenta and pseudorapidities at LHC energies and present the transverse momentum and rapidity distributions of the charged leptons.

    hep-phPoS(2016)·33 citations
24. 24*

    Integrand-reduction techniques for NLO and beyond

    Giovanni Ossola🇺🇸

    After a brief general introduction about the integrand-reduction method, we will review the main features of the GoSam 2.0 automated framework for one-loop calculations and illustrate its application to SM processes involving the production of massive particles in conjunction with jets and photons. These results have been obtained by interfacing GoSam with different Monte Carlo frameworks, thus combining the NLO calculation with parton shower effects. In the second part of the presentation, we will focus on the applications of GoSam beyond NLO. The code has already been used within NNLO calculations for the computation of real-virtual contributions and for the evaluation of the hard functions needed by approximate NNLO and resummation techniques. We will finally briefly discuss a promising approach for the reduction of scattering amplitudes beyond one loop based on integrand reduction via multivariate polynomial division.

    hep-phPoS(2016)·0 citations
25. 25*

    Bubble dynamics and the quark-hadron phase transition in nuclear collisions

    D. A. Fogaça🇧🇷 · S. M. Sanches Jr.🇧🇷 · R. Fariello🇧🇷 · F. S. Navarra🇧🇷

    We study the nucleation of a quark gluon plasma (QGP) phase in a hadron gas at low temperatures and high baryon densities. This kind of process will presumably happen very often in nuclear collisions at FAIR and NICA. When the appropriate energy densities (or baryon densities) and temperatures are reached the conversion of one phase into another is not instantaneous. It is a complex process, which involves the nucleation of bubbles of the new phase. One important element of this transition process is the rate of growth of a QGP bubble. In order to estimate it we solve the Relativistic Rayleigh$-$Plesset equation which governs the dynamics of a relativistic spherical bubble in a strongly interacting medium. The baryon rich hadron gas is represented by the nonlinear Walecka model and the QGP is described by the MIT bag model and also by a mean field model of QCD.

    hep-phnucl-thPRC(2016)·7 citations
26. 26*

    Loop-tree duality and quantum field theory in four dimensions

    German F. R. Sborlini🇪🇸

    Loop-tree duality allows to express virtual contributions in terms of phase-space integrals, thus leading to a direct comparison with real radiation terms. In this talk, we review the basis of the method and describe its application to regularize Feynman integrals. Performing an integrand-level combination of real and virtual terms, we obtain finite contributions that can be computed in four-dimensions. Moreover, this method provides a natural physical interpretation of infrared singularities, their origin and the way that they cancel in the complete computation.

    hep-phhep-thPoS(2016)·20 citations
27. 27*

    $f_0(980)$ production in $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D_s^{+}\to {\pi }^{+}{K}^{+}{K}^{-}$ decays

    J. M. Dias🇧🇷 · F. S. Navarra🇧🇷 · M. Nielsen🇧🇷 · E. Oset🇪🇸

    We study the $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D_s^{+}\to {\pi }^{+}{K}^{+}{K}^{-}$ decays adopting a mechanism in which the $D_s^{+}$ meson decays weakly into a ${\pi }^{+}$ and a $q\bar{q}$ component, which hadronizes into two pseudoscalar mesons. The final state interaction between these two pseudoscalar mesons is taken into account by using the Chiral Unitary approach in coupled channels, which gives rise to the $f_0(980)$ resonance. Hence, we obtain the invariant mass distributions of the pairs ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ after the decay of that resonance and compare our theoretical amplitudes with those available from the experimental data. Our results are in a fair agreement with these data, and a $f_0(980)$ signal is seen in both the ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ distributions.

    hep-phPRD(2016)·36 citations
28. 28*

    Spontaneous symmetry breaking in the $S_3$-symmetric scalar sector

    D. Emmanuel-Costa🇵🇹 · O. M. Ogreid🇳🇴 · P. Osland🇳🇴 · M. N. Rebelo🇵🇹

    We present a detailed study of the vacua of the $S_3$-symmetric three-Higgs-doublet potential, specifying the region of parameters where these minimisation solutions occur. We work with a CP conserving scalar potential and analyse the possible real and complex vacua with emphasis on the cases in which the CP symmetry can be spontaneously broken. Results are presented both in the reducible-representation framework of Derman, and in the irreducible-representation framework. Mappings between these are given. Some of these implementations can in principle accommodate dark matter and for that purpose it is important to identify the residual symmetries of the potential after spontaneous symmetry breakdown. We are also concerned with constraints from vacuum stability.

    hep-phJHEP(2016)·50 citations
29. 29*

    An Effective Field Theory for Forward Scattering and Factorization Violation

    Ira Z. Rothstein🇺🇸 · Iain W. Stewart🇺🇸

    Starting with QCD, we derive an effective field theory description for forward scattering and factorization violation as part of the soft-collinear effective field theory (SCET) for high energy scattering. These phenomena are mediated by long distance Glauber gluon exchanges, which are static in time, localized in the longitudinal distance, where $|t|\ll s$. In hard scattering, Glauber gluons can induce corrections which invalidate factorization. With SCET, Glauber exchange graphs can be calculated explicitly, and are distinct from graphs with soft, collinear, or ultrasoft gluons. We derive a complete basis of operators which describe the leading power effects of Glauber exchange. Key ingredients include regulating light-cone rapidity singularities and subtractions which prevent double counting. Our results include a novel all orders gauge invariant pure glue soft operator which appears between two collinear rapidity sectors. The 1-gluon Feynman rule for the soft operator coincides with the Lipatov vertex, but it also contributes to emissions with $\ge 2$ soft gluons. Our Glauber operator basis is derived using tree level and one-loop matching calculations from full QCD to SCET. The rapidity RGE yields gluon Reggeization at the amplitude level, and gives the BFKL equation for the soft and collinear functions in the forward scattering cross section. We derive an explicit rule for when eikonalization is valid, and provide a direct connection to the picture of multiple Wilson lines crossing a shockwave. In hard scattering operators Glauber subtractions for soft and collinear loop diagrams ensure that we are not sensitive to the directions for soft and collinear Wilson lines. Conversely, certain Glauber interactions can be absorbed into these soft and collinear Wilson lines by taking them to be in specific directions. We also discuss criteria for factorization violation.

    hep-phhep-thnucl-thJHEP(2016)·236 citations
30. 30*

    Lepton mixing patterns from combinations of elementary correlations

    Shu-jun Rong🇨🇳

    Recent data of reactor neutrino experiments set more stringent constraint on leptonic mixing patterns. We examine all possible patterns on the basis of combinations of elementary correlations of elements of leptonic mixing matrix. we obtain 62 viable mixing patters at 3$\sigma$ level of mixing parameters. Most of these patterns can be paired via the {\mu}- interchange which changes the octant of ${\theta }_{23}$ and the sign of $\cos \delta$. All viable patterns can be classified into two groups: the perturbative patterns and non-perturbative patterns. The former can be obtained from perturbing TBM. The latter cannot be obtained from perturbing any mixing pattern whose ${\theta }_{13}$ is zero. Different predictions of Dirac CP phase $\delta$ of these two types of mixing patterns are discussed. Evolutions of mass matrices of neutrinos with small mixing parameters are discussed via special mixing patterns on the basis of flavor groups. In general cases, a small variation of $\sin {\theta }_{13}$ may bring about large modifications to alignment of vacuum expectation values in a mixing model. Therefore, small but nonzero $\sin {\theta }_{13}$ brings a severer challenge to leptonic mixing models on the basis of flavor groups than usual views.

    hep-phPRD(2016)·0 citations
31. 31*

    Parton distribution of nucleon and nuclear EMC effect in a statistical model

    Xian-Qiao Yu🇨🇳

    We study the parton distribution of nucleon and nuclear EMC effect in a statistical model. We find when we choose the parameters appropriately, the predictions given by pure statistical laws can fit the experimental data well in most range of $x$, this reveal statistical law play an important role in the parton distribution of nucleon.

    hep-ph1 citation
32. 32*

    Positive Signs in Massive Gravity

    Clifford Cheung🇺🇸 · Grant N. Remmen🇺🇸

    We derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. The high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small island in the parameter space of ghost-free massive gravity. While the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.

    ↳ hep-thgr-qchep-phJHEP(2016)·168 citations
33. 33*

    Tests of the Einstein Equivalence Principle using TeV Blazars

    Jun-Jie Wei🇨🇳 · Jie-Shuang Wang🇨🇳 · He Gao🇨🇳 · Xue-Feng Wu🇨🇳

    The observed time delays between different energy bands from TeV blazars provide a new interesting way of testing the Einstein Equivalence Principle (EEP). If the whole time delay is assumed to be dominated by the gravitational field of the Milky Way, the conservative upper limit on the EEP can be estimated. Here we show that the strict limits on the differences of the parameterized post-Newtonian parameter $\gamma$ values are ${\gamma }_{\mathrm{TeV}}-{\gamma }_{\mathrm{keV}}<3.86\times 10^{-3}$ for Mrk 421 and ${\gamma }_{\mathrm{TeV}}-{\gamma }_{\mathrm{keV}}<4.43\times 10^{-3}$ for Mrk 501, while expanding the scope of the tested EEP energy range out to the TeV--keV range for the first time. With the small time lag from the 0.2--0.8 TeV and $>0.8$ TeV light curves of PKS 2155-304, a much more severe constraint on $\gamma$ differences of $\sim 10^{-6}$ can be achieved, although the energy difference is of order of $\sim$ TeV. Furthermore, we can combine these limits on the energy dependence of $\gamma$ with the bound on the absolute $\gamma$ value $\gamma -1\sim 0.3\%$ from light deflection measurements at the optical (eV) bands, and conclude that this absolute bound on $\gamma$ can be extended from optical to TeV energies.

    ↳ astro-ph.HEgr-qchep-phhep-thApJL(2016)·44 citations
34. 34*

    Deeply Virtual Pseudoscalar Meson Production at Jefferson Lab and Transversity GPDs

    Valery Kubarovsky (Jefferson Lab) (for the CLAS Collaboration)🇺🇸

    The cross section of the exclusive ${\pi }^0$ and $\eta$ electroproduction reaction $ep\to e^{\prime }{p}^{\prime }{\pi }^0/\eta$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma /dtd{Q}^{2}d{x}_{B}d\varphi$ and structure functions ${\sigma }_T+ϵ{\sigma }_L,{\sigma }_{TT}$ and ${\sigma }_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. The data are compared with the GPD based theoretical models. Analyses find that a large dominance of transverse processes is necessary to explain the experimental results. Generalized form factors of the transversity GPDs $H_T^{\pi ,\eta }$ and ${\bar{E}}_T^{\pi ,\eta }$ were directly extracted from the experimental observables for the first time. It was found that GPD ${\bar{E}}_T$ dominates in pseudoscalar meson production. The combined ${\pi }^0$ and $\eta$ data opens the way for the flavor decomposition of the transversity GPDs. The first ever evaluation of this decomposition was demonstrated.

    ↳ hep-exhep-phnucl-exInt.J.Mod.Phys.Conf.Ser.(2016)·12 citations
35. 35*

    Violation of mass ordering for multi-strange hadrons at RHIC and LHC

    Shiori Takeuchi🇯🇵 · Koichi Murase🇯🇵 · Tetsufumi Hirano🇯🇵 · Pasi Huovinen🇩🇪 · Yasushi Nara🇯🇵

    We study effects of the hadronic rescattering on final observables especially for multi-strange hadrons such as $\varphi$, $\Xi$ and $\Omega$ in high-energy heavy-ion collisions within an integrated dynamical approach. In this approach, (3+1)-dimensional ideal hydrodynamics is combined with a microscopic transport model, JAM. We simulate the collisions with or without hadronic rescatterings and compare observables between these two options so that we quantify the effects of the hadronic rescattering. We find that the mean transverse momentum and the elliptic flow parameter of multi-strange hadrons are less affected by hadronic rescattering and, as a result, the mass ordering of the $p_T$-differential elliptic flow parameter $v_2(p_T)$ is violated: At the RHIC and the LHC energies the $v_2(p_T)$ for $\varphi$-mesons is larger than that for protons in the low-$p_T$ regions.

    ↳ nucl-thhep-phnucl-exNPA(2016)·3 citations
36. 36*

    Towards a four-loop form factor

    Rutger Boels🇩🇪 · Bernd A. Kniehl🇩🇪 · Gang Yang🇩🇪

    The four-loop, two-point form factor contains the first non-planar correction to the lightlike cusp anomalous dimension. This anomalous dimension is a universal function which appears in many applications. Its planar part in N = 4 SYM is known, in principle, exactly from AdS/CFT and integrability while its non-planar part has been conjectured to vanish. The integrand of the form factor of the stress-tensor multiplet in N = 4 SYM including the non-planar part was obtained in previous work. We parametrise the difficulty of integrating this integrand. We have obtained a basis of master integrals for all integrals in the four-loop, two-point class in two ways. First, we computed an IBP reduction of the integrand of the N = 4 form factor using massive computer algebra (Reduze). Second, we computed a list of master integrals based on methods of the Mint package, suitably extended using Macaulay2 / Singular. The master integrals obtained in both ways are consistent with some minor exceptions. The second method indicates that the master integrals apply beyond N = 4 SYM, in particular to QCD. The numerical integration of several of the master integrals will be reported and remaining obstacles will be outlined

    ↳ hep-thhep-phPoS(2016)·0 citations
37. 37*

    Transverse momentum-flow correlations in relativistic heavy-ion collisions

    Piotr Bozek🇵🇱

    The correlation between the transverse momentum and the azimuthal asymmetry the flow is studied. A correlation coefficient is defined between the average transverse momentum of hadrons emitted in an event and the square of the elliptic or triangular flow coefficient. The hydrodynamic model predicts a positive correlation of the transverse momentum with the elliptic flow, and almost no correlation with the triangular flow in Pb-Pb collisions at LHC energies. In p-Pb collisions the new correlation observable is very sensitive to the mechanism of energy deposition in the first stage of the collision.

    ↳ nucl-thhep-phnucl-exPRC(2016)·119 citations
38. 38*

    Double copies of fermions as only gravitational interacting matter

    Leonardo de la Cruz🇩🇪 · Alexander Kniss🇩🇪 · Stefan Weinzierl🇩🇪

    Inspired by the recent progress in the field of scattering amplitudes, we discuss hypothetical particles which can be characterised as the double copies of fermions -- in the same way gravitons can be viewed as double copies of gauge bosons. As the gravitons, these hypothetical particles interact only through gravitational interactions. We present two equivalent methods for the computation of the relevant scattering amplitudes. The hypothetical particles can be massive and non-relativistic.

    ↳ hep-thgr-qchep-phPRL(2016)·26 citations
39. 39*

    Large volume supersymmetry breaking without decompactification problem

    Herve Partouche🇫🇷

    We consider heterotic string backgrounds in four-dimensional Minkowski space, where N=1 supersymmetry is spontaneously broken at a low scale m_{3/2} by a stringy Scherk-Schwarz mechanism. We review how the effective gauge couplings at 1-loop may evade the "decompactification problem", namely the proportionality of the gauge threshold corrections, with the large volume of the compact space involved in the supersymmetry breaking.

    ↳ hep-thhep-phSpringer Proc.Math.Stat.(2016)·6 citations
40. 40*

    Pionic dispersion relations in the presence of a weak magnetic field

    Souvik Priyam Adhya🇮🇳 · Mahatsab Mandal🇮🇳 · Subhrajyoti Biswas🇮🇳 · Pradip K. Roy🇮🇳

    In this work, dispersion relations of ${\pi }^0$ and ${\pi }^{\pm }$ have been studied in vacuum in the limit of weak external magnetic field using a phenomenological pion-nucleon $(\pi N)$ Lagrangian. For our purpose, we have calculated the results up to one loop order in self energy diagrams with the pseudoscalar $(PS)$ and pseudovector $(PV)$ pion-nucleon interactions. By assuming weak external magnetic field it is seen that the effective mass of pion gets explicit magnetic field dependence and it is modified significantly for the case of PS coupling. However, for the PV coupling, only a modest increase in the effective mass is observed. These modified dispersion relations due to the presence of the external field can have substantial influence in the phenomenological aspect of the mesons both in the context of neutron stars as well as relativistic heavy ion collisions.

    ↳ nucl-thhep-phPRD(2016)·18 citations
41. 41*

    Constancy of the Cluster Gas Mass Fraction in the R_h=ct Universe

    Fulvio Melia🇺🇸

    The ratio of baryonic to dark matter densities is assumed to have remained constant throughout the formation of structure. With this, simulations show that the fraction f_gas(z) of baryonic mass to total mass in galaxy clusters should be nearly constant with redshift z. However, the measurement of these quantities depends on the angular distance to the source, which evolves with z according to the assumed background cosmology. An accurate determination of f_gas(z) for a large sample of hot (kT_e > 5 keV), dynamically relaxed clusters could therefore be used as a probe of the cosmological expansion up to z < 2. The fraction f_gas(z) would remain constant only when the "correct" cosmology is used to fit the data. In this paper, we compare the predicted gas mass fractions for both LCDM and the R_h=ct Universe and test them against the 3 largest cluster samples. We show that R_h=ct is consistent with a constant f_gas in the redshift range z < 2, as was previously shown for the reference LCDM model (with parameter values H_0=70 km/s/Mpc, Omega_m=0.3 and w_de=-1). Unlike LCDM, however, the R_h=ct Universe has no free parameters to optimize in fitting the data. Model selection tools, such as the Akaike Information Criterion (AIC) and the Bayes Information Criterion (BIC), therefore tend to favour R_h=ct over LCDM. For example, the BIC favours R_h=ct with a likelihood of ~95% versus ~5% for LCDM.

    ↳ astro-ph.COastro-ph.GAastro-ph.HEhep-phProc.Roy.Soc.Lond.A(2016)·13 citations
42. 42*

    Theoretical developments in supernova neutrino physics : mass corrections and pairing correlators

    Cristina Volpe🇫🇷

    We highlight the progress in our understanding of how neutrinos change their flavor in astrophysical environments, in particular effects from the neutrino self-interaction. We emphasize extended descriptions of neutrino propagation in massive stars that are beyond the current one based on the mean-field approximation. The extended equations include, in particular, corrections from (anti)neutrino-(anti)neutrino pairing correlations and from the neutrino mass. We underline open issues and challenges.

    ↳ astro-ph.HEastro-ph.SRhep-phJ.Phys.Conf.Ser.(2016)·7 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.