Wed·Feb 24, 2016Wednesday·February 24, 2016

1. 01*

   Reducing the fine-tuning of gauge-mediated SUSY breaking

   J. Alberto Casas🇪🇸 · Jesus M. Moreno🇪🇸 · Sandra Robles🇪🇸 · Krzysztof Rolbiecki🇪🇸

   Despite their appealing features, models with gauge-mediated supersymmetry breaking (GMSB) typically present a high degree of fine-tuning, due to the initial absence of the top trilinear scalar couplings, $A_t=0$. In this paper, we carefully evaluate such a tuning, showing that is worse than per mil in the minimal model. Then, we examine some existing proposals to generate $A_t\ne 0$ term in this context. We find that, although the stops can be made lighter, usually the tuning does not improve (it may be even worse), with some exceptions, which involve the generation of $A_t$ at one loop or tree level. We examine both possibilities and propose a conceptually simplified version of the latter; which is arguably the optimum GMSB setup (with minimal matter content), concerning the fine-tuning issue. The resulting fine-tuning is better than one per mil, still severe but similar to other minimal supersymmetric standard model constructions. We also explore the so-called "little $A_t^2/m^2$ problem", i.e. the fact that a large $A_t$-term is normally accompanied by a similar or larger sfermion mass, which typically implies an increase in the fine-tuning. Finally, we find the version of GMSB for which this ratio is optimized, which, nevertheless, does not minimize the fine-tuning.

   hep-phEPJC(2016)·11 citations
2. 02*

   Proper definition and evolution of generalized transverse momentum distributions

   Miguel G. Echevarria🇪🇸 · Ahmad Idilbi🇺🇸 · Koichi Kanazawa🇺🇸 · Cédric Lorcé🇫🇷 · Andreas Metz🇺🇸 · Barbara Pasquini🇮🇹 · Marc Schlegel🇩🇪

   We consider one of the most fundamental sets of hadronic matrix elements, namely the generalized transverse momentum distributions (GTMDs), and argue that their existing definitions lack proper evolution properties. By exploiting the similarity of GTMDs with the much better understood transverse momentum distributions, we argue that the existing definitions of GTMDs have to include an additional dependence on soft gluon radiation in order to render them properly defined. With this, we manage to obtain the evolution kernel of all (un)polarized quark and gluon GTMDs, which turns out to be spin independent. As a byproduct, all large logarithms can be resummed up to next-to-next-to-leading-logarithmic accuracy with the currently known perturbative ingredients.

   hep-phPLB(2016)·63 citations
3. 03*

   Fully-Automated Precision Predictions for Heavy Neutrino Production Mechanisms at Hadron Colliders

   Celine Degrande🇬🇧 · Olivier Mattelaer🇬🇧 · Richard Ruiz🇬🇧 · Jessica Turner🇬🇧

   Motivated by TeV-scale neutrino mass models, we propose a systematic treatment of heavy neutrino $(N)$ production at hadron colliders. Our simple and efficient modeling of the vector boson fusion (VBF) $W^{\pm }\gamma \to N{\ell }^{\pm }$ and $N{\ell }^{\pm }+nj$ signal definitions resolve collinear and soft divergences that have plagued past studies, and is applicable to other color-singlet processes, e.g., associated Higgs $(W^{\pm }h)$, sparticle $({\tilde{\ell }}^{\pm }\widetilde{{\nu }_{\ell }})$, and charged Higgs $(h^{\pm \pm }{h}^{\mp })$ production. We present, for the first time, a comparison of all leading $N$ production modes, including both gluon fusion (GF) $gg\to Z^{\ast }/h^{\ast }\to N\stackrel{(-)}{{\nu }_{\ell }}$ and VBF. We obtain fully differential results up to next-to-leading order (NLO) in QCD accuracy using a Monte Carlo tool chain linking FeynRules, N{\small LO}CT, and MadGraph5\_aMC@NLO. Associated model files are publicly available. At the 14 TeV LHC, the leading order GF rate is small and comparable to the NLO $N{\ell }^{\pm }+1j$ rate; at a future 100 TeV Very Large Hadron Collider, GF dominates for $m_N=300-1500$ GeV, beyond which VBF takes lead.

   hep-phhep-exPRD(2016)·194 citations
4. 04*

   W-boson plus jet differential distributions at NNLO in QCD

   Radja Boughezal🇺🇸 · Xiaohui Liu🇺🇸 · Frank Petriello🇺🇸

   We present a detailed phenomenological study of W-boson production in association with a jet through next-to-next-to-leading order (NNLO) in perturbative QCD. Fiducial cross sections and differential distributions for both 8 TeV and 13 TeV LHC collisions are presented, as are results for both the inclusive one-jet bin and the exclusive one-jet bin. Two different event selection criteria are considered: a general selection with standard cuts used in experimental analyses, and a boosted selection that focuses on high transverse momentum jets. We discuss the higher-order corrections in detail and identify for which observables and phase space regions the QCD perturbative expansion is under good theoretical control, and where additional work is needed. For most distributions and phase space regions the QCD perturbative expansion exhibits good convergence after the inclusion of the NNLO corrections.

   hep-phhep-exPRD(2016)·111 citations
5. 05*

   Generalized focus point and mass spectra comparison of highly natural SUGRA GUT models

   Howard Baer🇺🇸 · Vernon Barger🇺🇸 · Michael Savoy🇺🇸

   Supergravity grand unified models (SUGRA GUTs) are highly motivated and allow for a high degree of electroweak naturalness when the superpotential parameter mu~ 100-300 GeV (preferring values closer to 100 GeV). We first illustrate that models with radiatively-driven naturalness enjoy a generalized focus-point behavior wherein all soft terms are correlated instead of just scalar masses. Next, we generate spectra from four SUGRA GUT archetypes: 1. SO(10) models where the Higgs doublets live in different 10-dimensional irreducible representations (irreps), 2. models based on SO(10) where the Higgs multiplets live in a single 10-dimensional irrep but with D-term scalar mass splitting, 3. models based on SU(5) and 4. a more general SUGRA model with 12 independent parameters. Electroweak naturalness implies for all models a spectrum of light higgsinos with m(higgsinos)< 300 GeV and gluinos with m(gluino)< 2-4 TeV. However, masses and mixing in the third generation sfermion sector differ distinctly between the models. These latter differences would be most easily tested at a linear e^+e^- collider with \sqrt{s}~ multi-TeV-scale but measurements at a 50-100 TeV hadron collider are also possible.

   hep-phPRD(2016)·10 citations
6. 06*

   Vector and axial vector mesons in a nonlocal chiral quark model

   M.F. Izzo Villafañe🇦🇷 · D. Gomez Dumm🇦🇷 · N.N. Scoccola🇦🇷

   Basic features of nonstrange vector and axial vector mesons are analyzed in the framework of a chiral quark model that includes nonlocal four fermion couplings. Unknown model parameters are determined from some input values of masses and decay constants, while nonlocal form factors are taken from a fit to lattice QCD results for effective quark propagators. Numerical results show a good agreement with the observed meson phenomenology.

   hep-phPRD(2016)·9 citations
7. 07*

   Future Colliders Symposium in Hong Kong: Scientific Overview

   Chris Quigg🇺🇸

   Opening Lecture at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, January 18--21, 2016.

   hep-phhep-exInt.J.Mod.Phys.A(2016)·1 citation
8. 08*

   Charmless $B_c$ $\to$ $PP$, $PV$ decays in the QCD factorization approach

   Na Wang🇨🇳

   The charmless $B_c$ $\to$ $PP$, $PV$~(where $P$ and $V$ denote the light pseudoscalar and vector mesons, respectively) decays can occur only via the weak annihilation diagrams within the Standard Model and provide, therefore, an ideal place to probe the strength of annihilation contribution in hadronic $B_{u,d,s}$ decays. In this paper, we study these kinds of decays in the framework of QCD factorization, by adopting two different schemes: scheme I is similar to the method usually adopted in the QCD factorization approach, while scheme II is based on the infrared behavior of gluon propagator and running coupling. For comparison, in our calculation, we adopt three kinds of wave functions for $B_c$ meson. It is found that: (a) The predicted branching ratios in scheme I are, however, quite small and are almost impossible to be measured at the LHCb experiment. (b) In scheme II, by assigning a dynamical gluon mass to the gluon propagator, we can avoid enhancements of the contribution from soft endpoint region. The strength of annihilation contributions predicted in scheme II is enhanced compared to that obtained in scheme I. However, the predicted branching ratios are still smaller than the corresponding ones obtained in the perturbative QCD approach. The large discrepancies among these theoretical predictions indicate that more detailed studies of these decays are urgently needed and will be tested by the future measurements performed at the LHCb experiment.

   hep-phAdv.High Energy Phys.(2016)·7 citations
9. 09*

   Understanding the nature of the heavy pentaquarks and searching for them in pion-induced reactions

   Xiao-Hai Liu🇯🇵 · Makoto Oka🇯🇵

   We investigate the reaction ${\pi }^{-}p\to {\pi }^{-}J/\psi p$ via the open-charm hadron rescattering diagrams. Due to the presence of the triangle singularity (TS) in the rescattering amplitudes, the TS peaks can simulate the pentaquark-like resonances arising in the $J/\psi p$ invariant mass distributions, which may bring ambiguities on our understanding of the nature of the exotic states. Searching for the heavy pentaquark in different processes may help us to clarify the ambiguities, because of the highly process-dependent characteristic of the TS mechanism.

   hep-phhep-exnucl-exnucl-thNPA(2016)·39 citations
10. 10*

    CP-Violation and Non-Standard Interactions at the MOMENT

    Pouya Bakhti🇮🇷 · Yasaman Farzan🇮🇷

    To measure the last unknown $3\nu$ oscillation parameter ($\delta$), several long baseline neutrino experiments have been designed or proposed. Recently it has been shown that turning on neutral current Non-Standard Interactions (NSI) of neutrinos with matter can induce degeneracies that may even hinder the proposed state-of-the-art DUNE long baseline experiment from measuring the value of $\delta$. We study how the result of the proposed MOMENT experiment with a baseline of 150 km and $200\mathrm{MeV}<E_{\nu }<600\mathrm{MeV}$ can help to solve the degeneracy induced by NSI and determine the true value of $\delta$.

    hep-phJHEP(2016)·57 citations
11. 11*

    Confronting a New Three-loop Seesaw Model with the 750 GeV Diphoton Excess

    P. Ko🇰🇷 · Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼 · Yuta Orikasa🇰🇷

    We propose a new type of radiative neutrino model with a local hidden $U(1)$ symmetry, in which neutrino masses are induced at the three loop level, and discuss the muon anomalous magnetic moment, and dark matter candidates therein. By allowing the hypercharges larger than 3/2 for new fields that contribute to the neutrino masses and making them decay into the standard model fields appropriately, we introduce a lot of new particles with multiple electrical charges in a natural manner. As a by-product, we can accommodate the 750 GeV diphoton excess depending on the hypercharge quantum numbers of new fields responsible for the neutrino masses at the three loop level.

    hep-phPRD(2016)·40 citations
12. 12*

    Hard gluon evolution of nucleon Generalized parton distributions in the Light-front quark model

    Neetika Sharma🇮🇳

    We incorporate the perturbative evolution effects in the generalized parton distributions (GPDs) calculated in effective light-front quark model for the nucleon. The perturbative effects enters into formalism through the evolution of GPDs according to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-like (DGLAP) equation. We obtain the evolved GPDs in the momentum space and transverse impact parameter space. We observe that combining the light front quark model with the perturbative evolution effects, give the effective model for studying the phenomenological GPDs

    hep-phEPJA(2016)·2 citations
13. 13*

    UV (in)sensitivity of Higgs inflation

    Jacopo Fumagalli🇳🇱 · Marieke Postma🇳🇱

    The predictions of Standard Model Higgs inflation are in excellent agreement with the Planck data, without the need for new fields. However, consistency of the theory requires the presence of (unknown) threshold corrections. These modify the running of the couplings, and thereby change the shape of the inflationary potential. This raises the question how sensitive the CMB parameters are to the UV completion. We show that, due to a precise cancellation, the inflationary predictions are almost unaffected. This implies in general that one cannot relate the spectral index and tensor-to-scalar ratio to the precise top and Higgs mass measurements at the LHC, nor can one probe effects of UV physics on the running.

    hep-phastro-ph.COJHEP(2016)·73 citations
14. 14*

    A search for Secluded Dark Matter in the Sun with the ANTARES neutrino telescope

    S. Adrián-Martínez🇪🇸 · A. Albert🇫🇷 · M. André🇪🇸 · G. Anton🇩🇪 · M. Ardid🇪🇸 · J.-J. Aubert🇫🇷 · T. Avgitas🇫🇷 · B. Baret🇫🇷 · J. Barrios-Martí🇪🇸 · S. Basa🇫🇷 · V. Bertin🇫🇷 · S. Biagi🇮🇹 and 106 other authors

    A search for Secluded Dark Matter annihilation in the Sun using 2007-2012 data of the ANTARES neutrino telescope is presented. Three different cases are considered: a) detection of dimuons that result from the decay of the mediator, or neutrino detection from: b) mediator that decays into a dimuon and, in turn, into neutrinos, and c) mediator that decays directly into neutrinos. As no significant excess over background is observed, constraints are derived on the dark matter mass and the lifetime of the mediator.

    ↳ hep-exastro-ph.HEhep-phJCAP(2016)·70 citations
15. 15*

    Cumulants of multiplicity distributions in most-central heavy-ion collisions

    Hao-jie Xu🇨🇳

    I investigate the volume corrections on cumulants of total charge distributions and net proton distributions. The required volume information is generated by an optical Glauber model. I find that the corrected statistical expectations of multiplicity distributions mimic the negative binomial distributions at non-central collisions, and they tend to approach the Poisson ones at most-central collisions due to the "boundary effects," which suppress the volume corrections. However, net proton distributions and reference multiplicity distributions are sensitive to the external volume fluctuations at most-central collisions, which imply that one has to consider the details of volume distributions in event-by-event multiplicity fluctuation studies.

    ↳ nucl-thhep-phnucl-exPRC(2016)·20 citations
16. 16*

    Direct extraction of nuclear effects in quasielastic scattering on carbon

    Callum Wilkinson🇨🇭 · Kevin S. McFarland🇺🇸

    Nuclear effects on neutrino reactions are expected to be a significant complication in current and future neutrino oscillation experiments seeking precision measurements of neutrino flavor transitions. Calculations of these nuclear effects are hampered by a lack of experimental data comparing neutrino reactions on free nucleons to neutrino reactions on nuclei. We present results from a novel technique that compares neutrino and antineutrino charged current quasielastic scattering on hydrocarbons to extract a cross section ratio of antineutrino charged current elastic reactions on free protons to charged current quasielastic reactions on the protons bound in a carbon nucleus. This measurement of nuclear effects is compared to models.

    ↳ hep-exhep-phnucl-exPRD(2016)·2 citations
17. 17*

    Phenomena at the QCD phase transition in nonequilibrium chiral fluid dynamics (N$\chi$FD)

    Marlene Nahrgang🇺🇸 · Christoph Herold🇹🇭

    Heavy-ion collisions performed in the beam energy range accessible by the NICA collider facility are expected to produce systems of extreme net-baryon densities and can thus reach yet unexplored regions of the QCD phase diagram. Here, one expects the phase transition between the plasma of deconfined quarks and gluons and the hadronic matter to be of first order. A discovery of the first-order phase transition would as well prove the existence of the QCD critical point, a landmark in the phase diagram. In order to understand possible signals of the first-order phase transition in heavy-ion collision experiments it is very important to develop dynamical models of the phase transition. Here, we discuss the opportunities of studying dynamical effects at the QCD first-order phase transition within our model of nonequilibrium chiral fluid dynamics.

    ↳ nucl-thhep-phEPJA(2016)·9 citations
18. 18*

    Making extreme computations possible with virtual machines

    J. Reuter🇩🇪 · B. Chokoufe🇩🇪 · T. Ohl🇩🇪

    State-of-the-art algorithms generate scattering amplitudes for high-energy physics at leading order for high-multiplicity processes as compiled code (in Fortran, C or C++). For complicated processes the size of these libraries can become tremendous (many GiB). We show that amplitudes can be translated to byte-code instructions, which even reduce the size by one order of magnitude. The byte-code is interpreted by a Virtual Machine with runtimes comparable to compiled code and a better scaling with additional legs. We study the properties of this algorithm, as an extension of the Optimizing Matrix Element Generator (O'Mega). The bytecode matrix elements are available as alternative input for the event generator WHIZARD. The bytecode interpreter can be implemented very compactly, which will help with a future implementation on massively parallel GPUs.

    ↳ physics.comp-phhep-exhep-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.