Fri·Nov 20, 2015Friday·November 20, 2015

1. 01*

   Dynamical fine-tuning of initial conditions for small field inflations

   Satoshi Iso🇯🇵 · Kazunori Kohri🇯🇵 · Kengo Shimada🇫🇷

   Small-field inflation (SFI) is widely considered to be unnatural because an extreme fine-tuning of the initial condition is necessary for sufficiently large e-folding. In this paper, we show that the unnaturally-looking initial condition can be dynamically realised without any fine-tuning if the SFI occurs after rapid oscillations of the inflaton field and particle creations by preheating. In fact, if the inflaton field $\varphi$ is coupled to another scalar field $\chi$ through the interaction $g^2{\chi }^2{\varphi }^2$ and the vacuum energy during the small field inflation is given by $\lambda M^4$, the initial value can be dynamically set at $(\sqrt{\lambda }/g)M^2/M_{\mathrm{pl}}$, which is much smaller than the typical scale of the potential $M.$ This solves the initial condition problem in the new inflation model or some classes of the hilltop inflation models.

   hep-phastro-ph.COhep-thPRD(2016)·8 citations
2. 02*

   The Bino Variations: Effective Field Theory Methods for Dark Matter Direct Detection

   Asher Berlin🇺🇸 · Denis S. Robertson🇺🇸 · Mikhail P. Solon🇺🇸 · Kathryn M. Zurek🇺🇸

   We apply effective field theory methods to compute bino-nucleon scattering, in the case where tree-level interactions are suppressed and the leading contribution is at loop order via heavy flavor squarks or sleptons. We find that leading log corrections to fixed-order calculations can increase the bino mass reach of direct detection experiments by a factor of two in some models. These effects are particularly large for the bino-sbottom coannihilation region, where bino dark matter as heavy as 5-10 TeV may be detected by near future experiments. For the case of stop- and selectron-loop mediated scattering, an experiment reaching the neutrino background will probe thermal binos as heavy as 500 and 300 GeV, respectively. We present three key examples that illustrate in detail the framework for determining weak scale coefficients, and for mapping onto a low energy theory at hadronic scales, through a sequence of effective theories and renormalization group evolution. For the case of a squark degenerate with the bino, we extend the framework to include a squark degree of freedom at low energies using heavy particle effective theory, thus accounting for large logarithms through a "heavy-light current." Benchmark predictions for scattering cross sections are evaluated, including complete leading order matching onto quark and gluon operators, and a systematic treatment of perturbative and hadronic uncertainties.

   hep-phastro-ph.COPRD(2016)·35 citations
3. 03*

   The CTA aims at the Inert Doublet Model

   Farinaldo S. Queiroz🇩🇪 · Carlos E. Yaguna🇩🇪

   We show that the Cherenkov Telescope Array (CTA) can realistically challenge the Inert Doublet Model, excluding its heavy regime up to dark matter masses of 800 GeV and probing a large fraction of the remaining viable parameter space at even higher masses. Two features of the Inert Doublet Model make it particularly suitable for CTA searches. First, the dark matter mass (in the heavy regime) must be larger than 500 GeV. Second, the dark matter annihilation cross section, $\sigma v$, is always larger than the thermal one, reaching values as high as $10^{-25}\mathrm{c}{\mathrm{m}}^3{\mathrm{s}}^{-1}$. This higher value of $\sigma v$ is the result of the unavoidable coannhilation effects that determine the relic density via thermal freeze-out in the early Universe. We find that with 100 hours of Galactic Center exposure, CTA's expected limit widely surpasses, even after the inclusion of systematic errors, current and projected bounds from Fermi-LAT and HESS on this model.

   hep-phastro-ph.HEJCAP(2016)·74 citations
4. 04*

   Affleck-Dine baryogenesis just after inflation

   Masaki Yamada🇯🇵

   We propose a new scenario of Affleck-Dine baryogenesis where a flat direction in the MSSM generates B-L asymmetry just after the end of inflation. The resulting amount of baryon asymmetry is independent of low-energy supersymmetric models but is dependent on inflation models. We consider the hybrid and chaotic inflation models and find that reheating temperature is required to be higher than that in the conventional scenario of Affleck-Dine baryogenesis. In particular, non-thermal gravitino-overproduction problem is naturally avoided in the hybrid inflation model. Our results imply that Affleck-Dine baryogenesis can be realized in a broader range of supersymmetry and inflation models than expected in the literature.

   hep-phastro-ph.COPRD(2016)·34 citations
5. 05*

   A Model of Quark and Lepton Mixing and Mass Hierarchy

   S.M. Barr🇺🇸 · Heng-Yu Chen🇺🇸

   It is shown that an idea proposed in 1996 that relates in a qualitatively correct way the inter-family mass hierarchies of the up quarks, down quarks, charged leptons, and neutrinos, can be combined with a predictive scheme recently proposed for relating quark mixing and neutrino mixing. In the resulting model, the entire flavor structure of the quarks and leptons is expressible in terms of two "master matrices": a diagonal matrix that gives the inter-family mass ratios, and an off-diagonal matrix that controls all flavor mixing.

   hep-phPRD(2016)·4 citations
6. 06*

   Mu_x boosted-bottom-jet tagging and Z-prime boson searches

   Keith Pedersen🇺🇸 · Zack Sullivan🇺🇸

   We present a new technique for tagging heavy-flavor jets with p_T > 500 GeV called "mu_x tagging." Current track-based methods of b-jet tagging lose efficiency and experience a large rise in fake rate in the boosted regime. Using muons from B hadron decay, we combine angular information and jet substructure to tag b jets, c jets, light jets, and "light-heavy" jets (those containing B hadrons from gluon splitting). We find tagging efficiencies of epsilon_b = 14%, epsilon_c = 6.5%, epsilon_{light-light} = 0.14%, and epsilon_{light-heavy} = 0.5%, respectively, that are nearly independent of transverse momentum at high energy. We demonstrate the usefulness of this new scheme by examining the discovery potential for multi-TeV leptophobic Z-prime bosons in the boosted-b-tagged dijet channel at the Large Hadron Collider.

   hep-phhep-exPRD(2016)·11 citations
7. 07*

   Neutral Higgs Boson Production at e+e- Colliders in the Complex MSSM: A Full One-Loop Analysis

   S. Heinemeyer🇪🇸 · C. Schappacher🇩🇪

   For the search for additional Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses in the Higgs sector a precise knowledge of their production properties is mandatory. We evaluate the cross sections for the neutral Higgs boson production at e^+e^- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production channels e^+e^- -> h_i Z, h_i gamma, h_i h_j (i,j = 1,2,3), including soft and hard QED radiation. The dependence of the Higgs boson production cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many cross sections. They are, depending on the production channel, roughly of 10-20% of the tree-level results, but can go up to 50% or higher. The full one-loop contributions are important for a future linear e^+e^- collider such as the ILC or CLIC. There are plans to implement the evaluation of the Higgs boson production cross sections into the code FeynHiggs.

   hep-phhep-exEPJC(2016)·34 citations
8. 08*

   Vector leptoquark resolution of $R_K$ and $R_{D^{(\ast )}}$ puzzles

   Svjetlana Fajfer🇸🇮 · Nejc Košnik🇸🇮

   We propose that three recent anomalies in $B$ meson decays, $R_{D^{(\ast )}}$, $R_K$, and $P_5^{\prime }$, might be explained by a single vector leptoquark weak triplet state. The constraints on the parameter space are obtained by considering $t\to b{\tau }^{+}\nu$ data, lepton flavor universality tests in the kaon sector, bounds on $B\to K^{(\ast )}\bar{\nu }\nu$, bound on the lepton flavor violating decay $B\to K\mu \tau$, and measurements of $b\to c{\mu }^{-}\bar{\nu }$ decays. The presence of such vector leptoquark could be exposed in precise measurements of $t\to b\tau \nu$ and $B\to K^{(\ast )}\bar{\nu }\nu$ decays. The model also predicts approximate equality of lepton flavor universality ratios $R_{K^{\ast }}$, $R_K$, and suppressed branching fraction of $B_s\to {\mu }^{+}{\mu }^{-}$.

   hep-phhep-exPLB(2016)·323 citations
9. 09*

   Combining $Q_T$ and small-$x$ resummations

   Simone Marzani🇺🇸

   We analyze transverse momentum ($Q_T$) resummation of a colorless final state, e.g. Higgs production in gluon fusion or the production of a lepton pair via the Drell-Yan mechanism, in the limit where the invariant mass of the final state is much less then the center-of-mass energy, i.e. $Q^2\ll s$. We show how the traditional resummation of logarithms of $Q_T/Q$ can be supplemented with the resummation of the leading logarithmic contributions at small $x=Q^2/s$ and we compute the necessary ingredients to perform such joint resummation.

   hep-phPRD(2016)·65 citations
10. 10*

    QCD Evolution of Superfast Quarks

    Adam J. Freese🇺🇸 · Wim Cosyn🇧🇪 · Misak M. Sargsian🇺🇸

    Recent high-precision measurements of nuclear deep inelastic scattering at high x and moderate 6 < Q${}^2$ < 9GeV${}^2$ give a rare opportunity to reach the quark distributions in the {\it superfast} region, in which the momentum fraction of the nucleon carried by its constituent quark is larger than the total fraction of the nucleon at rest, x>1. We derive the leading-order QCD evolution equation for such quarks with the goal of relating the moderate-Q${}^2$ data to the two earlier measurements of superfast quark distributions at large 60 < Q${}^2$ < 200~GeV${}^2$. Since the high-Q${}^2$ measurements gave strongly contradictory estimates of the nuclear effects that generate superfast quarks, relating them to the high-precision, moderate-Q${}^2$ data through QCD evolution allows us to clarify this longstanding issue. Our calculations indicate that the moderate-Q${}^2$ data at $x\lesssim 1.05$ are in better agreement with the high-Q${}^2$ data measured in (anti)neutrino-nuclear reactions which require substantial high-momentum nuclear effects in the generation of superfast quarks. Our prediction for the high-Q${}^2$ and x>1.1 region is somewhat in the middle of the neutrino-nuclear and muon-nuclear scattering data.

    hep-phnucl-exnucl-thPRD(2019)·12 citations
11. 11*

    Jet Fragmentation and Jet Shapes in JEWEL and Q-PYTHIA

    Marco van Leeuwen🇳🇱

    A study of several observables characterising fragment distributions of medium-modified parton showers using the JEWEL and Q-PYTHIA models is presented, with emphasis on the relation between the different observables.

    hep-phNucl.Part.Phys.Proc.(2016)·6 citations
12. 12*

    Supersymmetry Searches in GUT Models with Non-Universal Scalar Masses

    M. Cannoni🇪🇸 · J. Ellis🇬🇧 · M. E. Gómez🇪🇸 · S. Lola🇬🇷 · R. Ruiz de Austri🇪🇸

    We study SO(10), SU(5) and flipped SU(5) GUT models with non-universal soft supersymmetry-breaking scalar masses, exploring how they are constrained by LHC supersymmetry searches and cold dark matter experiments, and how they can be probed and distinguished in future experiments. We find characteristic differences between the various GUT scenarios, particularly in the coannihilation region, which is very sensitive to changes of parameters. For example, the flipped SU(5) GUT predict the possibility of ${\tilde{t}}_1-\chi$ coannihilation, which is absent in the regions of the SO(10) and SU(5) GUT parameter spaces that we study. We use the relic density predictions in different models to determine upper bounds for the neutralino masses, and we find large differences between different GUT models in the sparticle spectra for the same LSP mass, leading to direct connections of distinctive possible experimental measurements with the structure of the GUT group. We find that future LHC searches for generic missing $E_T$, charginos and stops will be able to constrain the different GUT models in complementary ways, as will the Xenon 1 ton and Darwin dark matter scattering experiments and future FERMI or CTA $\gamma$-ray searches.

    hep-phJCAP(2016)·12 citations
13. 13*

    Radiative corrections to the Higgs boson couplings in the model with an additional real singlet scalar field

    Shinya Kanemura🇯🇵 · Mariko Kikuchi🇯🇵 · Kei Yagyu🇬🇧

    We calculate renormalized Higgs boson couplings with gauge bosons and fermions at the one-loop level in the model with an additional isospin singlet real scalar field. These coupling constants can deviate from the predictions in the standard model due to tree-level mixing effects and one-loop contributions of the extra neutral scalar boson. We investigate how they can be significant under the theoretical constraints from perturbative unitarity and vacuum stability and also the condition of avoiding the wrong vacuum. Furthermore, comparing with the predictions in the Type I two Higgs doublet model, we numerically demonstrate how the singlet extension model can be distinguished and identified by using precision measurements of the Higgs boson couplings at future collider experiments.

    hep-phNPB(2016)·111 citations
14. 14*

    Electroweak Absolute, Meta-, and Thermal Stability in Neutrino Mass Models

    Manfred Lindner🇩🇪 · Hiren H. Patel🇩🇪 · Branimir Radovčić🇩🇪

    We analyze the stability of the electroweak vacuum in neutrino mass models containing right handed neutrinos or fermionic isotriplets. In addition to considering absolute stability, we place limits on the Yukawa couplings of new fermions based on metastability and thermal stability in the early Universe. Our results reveal that the upper limits on the neutrino Yukawa couplings can change significantly when the top quark mass is allowed to vary within the experimental range of uncertainty in its determination.

    hep-phPRD(2016)·18 citations
15. 15*

    Analysis of Charm Pair Production at the LHC

    D. Souza🇬🇧 · N.H. Brook🇬🇧

    The DGLAP and CCFM approaches to perturbative QCD evolution have been investigated by examining correlations of charmed hadron pairs in $pp$ collisions at $\sqrt{s}=7$ TeV. The theoretical models are compared to the data taken by the LHCb experiment. Differences in the parton kinematics between the two approaches are discussed. In general a model incorporating NLO diagrams matched to parton showers describes the data best.

    hep-phJ.Phys.G(2016)·6 citations
16. 16*

    Single pion contribution to the hyperfine splitting in muonic hydrogen

    Nguyen Thu Huong🇻🇳 · Emi Kou🇫🇷 · Bachir Moussallam🇫🇷

    A detailed discussion of the long-range one-pion exchange (Yukawa potential) contribution to the 2S hyperfine splitting in muonic hydrogen which had, until recently, been disregarded is presented. We evaluate the relevant vertex amplitudes, in particular ${\pi }^0{\mu }^{+}{\mu }^{-}$, combining low energy chiral expansions together with experimental data on ${\pi }^0$ and $\eta$ decays into two leptons. A value of $\Delta E_{HFS}^{\pi }=-(0.09\pm 0.06)\mu \mathrm{eV}$ is obtained for this contribution.

    hep-phPRD(2016)·26 citations
17. 17*

    Properties of magnetized neutral mesons within a full RPA evaluation

    Sidney S. Avancini🇧🇷 · William R. Tavares🇧🇷 · Marcus B. Pinto🇧🇷

    We consider the two flavor Nambu--Jona-Lasinio model within the RPA framework to evaluate the masses of the $\sigma$ and ${\pi }^0$ mesons and the ${\pi }^0$ decay constant in the presence of a magnetic field at vanishing temperatures and baryonic densities. The present work extends other RPA applications by fully considering the external momenta, which enter the integrals representing the magnetized polarization tensor, so that more accurate results can be obtained in the evaluation of physical quantities containing pionic contributions. As we show, this technical improvement generates results which agree well with those produced by lattice simulations and chiral perturbation theory. Our method may also prove to be useful in future evaluations of quantities such as the shear viscosity and the equation of state of magnetized quark matter with mesonic contributions.

    hep-phnucl-thPRD(2016)·76 citations
18. 18*

    Next-to-next-to-leading-order QCD corrections to ${\chi }_{c0,2}\to \gamma \gamma$

    Wen-Long Sang🇨🇳 · Feng Feng🇨🇳 · Yu Jia🇨🇳 · Shuang-Ran Liang🇨🇳

    We calculate the next-to-next-to-leading-order (NNLO) perturbative corrections to $P$-wave quarkonia annihilation decay to two photons, in the framework of nonrelativistic QCD (NRQCD) factorization. The order-${\alpha }_s^2$ short-distance coefficients associated with each helicity amplitude are presented in a semi-analytic form, including the "light-by-light" contributions. With substantial NNLO corrections, we find disquieting discrepancy when confronting our state-of-the-art predictions with the latest \textsf{BESIII} measurements, especially fail to account for the measured ${\chi }_{c2}\to \gamma \gamma$ width. Incorporating the effects of spin-dependent forces would even exacerbate the situation, since it lifts the degeneracy between the nonperturbative NRQCD matrix elements of ${\chi }_{c0}$ and ${\chi }_{c2}$ toward the wrong direction. We also present the order-${\alpha }_s^2$ predictions to ${\chi }_{b0,2}\to \gamma \gamma$, which await the future experimental test.

    hep-phhep-exPRD(2016)·30 citations
19. 19*

    Skew-Flavored Dark Matter

    Prateek Agrawal🇺🇸 · Zackaria Chacko🇺🇸 · Elaine C. F. S. Fortes🇧🇷 · Can Kilic🇺🇸

    We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects Minimal Flavor Violation, and is therefore naturally consistent with flavor constraints. We study the phenomenology of a benchmark model in which dark matter couples to right-handed charged leptons. In large regions of parameter space the dark matter can emerge as a thermal relic, while remaining consistent with the constraints from direct and indirect detection. The collider signatures of this scenario include events with multiple leptons and missing energy. These events exhibit a characteristic flavor pattern that may allow this class of models to be distinguished from other theories of dark matter.

    hep-phPRD(2016)·29 citations
20. 20*

    Neutrino mass limits: robust information from the power spectrum of galaxy surveys

    Antonio J. Cuesta🇪🇸 · Viviana Niro🇪🇸 · Licia Verde🇪🇸

    We present cosmological upper limits on the sum of active neutrino masses using large-scale power spectrum data from the WiggleZ Dark Energy Survey and from the Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG). Combining measurements on the Cosmic Microwave Background temperature and polarisation anisotropies by the Planck satellite together with WiggleZ power spectrum results in a neutrino mass bound of 0.37 eV at 95% C.L., while replacing WiggleZ by the SDSS-DR7 LRG power spectrum, the 95% C.L. bound on the sum of neutrino masses is 0.38 eV. Adding Baryon Acoustic Oscillation (BAO) distance scale measurements, the neutrino mass upper limits greatly improve, since BAO data break degeneracies in parameter space. Within a $\Lambda$CDM model, we find an upper limit of 0.13 eV (0.14 eV) at 95% C.L., when using SDSS-DR7 LRG (WiggleZ) together with BAO and Planck. The addition of BAO data makes the neutrino mass upper limit robust, showing only a weak dependence on the power spectrum used. We also quantify the dependence of neutrino mass limit reported here on the CMB lensing information. The tighter upper limit (0.13 eV) obtained with SDSS-DR7 LRG is very close to that recently obtained using Lyman-alpha clustering data, yet uses a completely different probe and redshift range, further supporting the robustness of the constraint. This constraint puts under some pressure the inverted mass hierarchy and favours the normal hierarchy.

    ↳ astro-ph.COhep-phPhys.Dark Univ.(2016)·157 citations
21. 21*

    Trapping effects in inflation: blue spectrum at small scales

    Edgar Bugaev🇷🇺 · Peter Klimai🇷🇺

    We consider the inflationary model in which the inflaton $\varphi$ couples to another scalar field $\chi$ via the interaction $g^2(\varphi -{\varphi }_0{)}^2{\chi }^2$ with a small coupling constant $g$ ($g^2\sim 10^{-7}$). We assume that there is a sequence of "trapping points" ${\varphi }_{0i}$ along the inflationary trajectory where particles of $\chi$-field become massless and are rather effectively produced. We calculate the power spectrum of inflaton field fluctuations originated from a backreaction of $\chi$-particles produced, using the Schwinger's "in-in" formalism. We show that the primary curvature power spectrum produced by these backreaction effects is blue, which leads to a strong overproduction of primordial black holes (PBHs) in subsequent radiation era.

    ↳ astro-ph.COhep-phPRD(2016)·4 citations
22. 22*

    Algebraic vacuum limits of QCD condensates from in-medium projections of Lorentz tensors

    Thomas Buchheim🇩🇪 · Burkhard Kampfer🇩🇪 · Thomas Hilger🇦🇹

    Utilizing the in-medium Lorentz decomposition of operators generating QCD condensates we derive general constraints among the latter ones by the requirement of a smooth transition from medium to vacuum. In this way we relate the vacuum limits of heretofore unrelated condensates and provide consistency checks for the vacuum saturation hypothesis and the heavy quark mass expansion. The results are general and depend only on the rank and symmetry of the Lorentz tensors to be decomposed. The derived prescription enables to uniquely and directly identify operator product expansion contributions which are algebraically specific for in-medium situations and in particular useful for operators with a higher rank, i.e. larger than three. Four-quark condensates in mass dimension six are exemplified.

    ↳ nucl-thhep-phJ.Phys.G(2016)·12 citations
23. 23*

    Hydrodynamic predictions for 5.02 TeV Pb-Pb collisions

    Jacquelyn Noronha-Hostler (Columbia U.)🇺🇸 · Matthew Luzum (Sao Paulo U. & Santiago de Compostela U.)🇧🇷 · Jean-Yves Ollitrault (IPhT, Saclay)🇫🇷

    We make predictions for momentum-integrated elliptic and triangular flow as well as mean transverse momentum for 5.02 TeV Pb-Pb collisions, as planned at the Large Hadron Collider. We use hydrodynamic calculations to predict the change of these observables as the center-of-mass collision energy evolves from 2.76 TeV to 5.02 TeV per nucleon pair. By using previously measured values as a baseline, we are able to make a robust prediction without relying on a particular model for initial conditions and without precise knowledge of medium properties such as viscosity. Thus, though the predicted changes are small, they can provide a significant test of the current hydrodynamic picture of heavy-ion collisions.

    ↳ nucl-thhep-phPRC(2016)·93 citations
24. 24*

    ChPT meets lattice: finite volume and partial quenching for masses, decay constants and VEVs at NNLO

    Thomas Rössler🇸🇪 · Johan Bijnens🇸🇪

    We discuss finite volume effects and partial quenching for Chiral Perturbation Theory in the mesonic sector. The effects are computed in terms of analytical expressions for masses, decay constants and vacuum expectation values (VEVs) to two-loop order. Numerical examples are presented for a number of interesting and relevant cases. All numerical programs are publically available, the prospects of a combination of these studies with lattice gauge theory computations are discussed briefly.

    ↳ hep-lathep-phPoS(2016)·0 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.