Mon·Aug 10, 2015Monday·August 10, 2015

1. 01*

   Drell-Yan Production at NNLL'+NNLO Matched to Parton Showers

   Simone Alioli🇨🇭 · Christian W. Bauer🇺🇸 · Calvin Berggren🇺🇸 · Frank J. Tackmann🇩🇪 · Jonathan R. Walsh🇺🇸

   We present results for Drell-Yan production from the GENEVA Monte-Carlo framework. We combine the fully-differential NNLO calculation with higher-order resummation in the 0-jettiness resolution variable. The resulting parton-level events are further combined with parton showering and hadronization provided by PYTHIA8. The 0-jettiness resummation is carried out to NNLL', which consistently incorporates all singular virtual and real NNLO corrections. It thus provides a natural perturbative connection between the NNLO calculation and the parton shower regime, including a systematic assessment of perturbative uncertainties. In this way, inclusive observables are correct to NNLO, up to small power corrections in the resolution cutoff. Furthermore, the perturbative accuracy of 0-jet-like resummation variables is significantly improved beyond the parton shower approximation. We provide comparisons with LHC measurements of Drell-Yan production at 7 TeV from ATLAS, CMS, and LHCb. As already observed in $e^{+}{e}^{-}$ collisions, for resummation-sensitive observables, the agreement with data is noticeably improved by using a lower value of ${\alpha }_s(M_Z)=0.1135$.

   hep-phhep-exPRD(2015)·188 citations
2. 02*

   Exotic Leptons: Collider and Muon Magnetic Moment Constraints

   D. Cogollo🇧🇷

   In light of the ongoing effort on reducing the theoretical uncertainties and an upcoming experiment concerning muon magnetic moment, we perform a detailed study of an 3-4-1 electroweak gauge extension of the standard model that contains exotic charged leptons in its spectrum. We discuss flavor changing neutral current, collider and electroweak bounds on the model and derive $1\sigma$ limits using current and projected limits on the muon magnetic moment. In summary, we exclude the masses of new gauge bosons that couple to muons and heavy charged leptons up to $700$~GeV. Moreover, we find a projected lower bound on the scale of symmetry breaking to be $2$~TeV.

   hep-phInt.J.Mod.Phys.A(2015)·15 citations
3. 03*

   Photoproduction of Exotic Baryon Resonances

   Marek Karliner🇮🇱 · Jonathan L. Rosner🇺🇸

   We point out that the new exotic resonances recently reported by LHCb in the $J/\psi p$ channel are excellent candidates for photoproduction off a proton target. This test is crucial to confirming the resonant nature of such states, as opposed to their being kinematical effects. We specialize to an interpretation of the heavier narrow state as a molecule composed of ${\Sigma }_c$ and ${\bar{D}}^{\ast }$, and estimate its production cross section using vector dominance. The relevant photon energies and fluxes are well within the capabilities of the GlueX and CLAS12 detectors at Thomas Jefferson National Accelerator Facility (JLAB). A corresponding calculation is also performed for photoproduction of an analogous resonance which is predicted to exist in the ${\rm Y}p$ channel.

   hep-phhep-exPLB(2016)·139 citations
4. 04*

   Is the Higgs Mechanism of Fermion Mass Generation a Fact? A Yukawa-less First-Two-Generation Model

   Diptimoy Ghosh🇮🇱 · Rick Sandeepan Gupta🇮🇱 · Gilad Perez🇮🇱

   It is now established that the major source of electroweak symmetry breaking (EWSB) is due to the observed Higgs particle. However, whether the Higgs mechanism is responsible for the generation of all the fermion masses, in particular, the fermions of the first two generations, is an open question. In this letter we present a construction where the light fermion masses are generated through a secondary, subdominant and sequestered source of EWSB. This fits well with the approximate U(2) global symmetry of the observed structure of the flavor sector. We first realize the above idea using a calculable two Higgs doublet model. We then show that the first two generation masses could come from technicolor dynamics, while the third generation fermions, as well as the electroweak gauge bosons get their masses dominantly from the Higgs mechanism. We also discuss how the small CKM mixing between the first two generations and the third generation, and soft mixing between the sequestered EWSB components arise in this setup. A typical prediction of this scenario is a significant reduction of the couplings of the observed Higgs boson to the first two generation of fermions.

   hep-phPLB(2016)·85 citations
5. 05*

   XCone: N-jettiness as an Exclusive Cone Jet Algorithm

   Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Jesse Thaler🇺🇸 · Christopher K. Vermilion🇺🇸 · Thomas F. Wilkason🇺🇸

   We introduce a new jet algorithm called XCone, for eXclusive Cone, which is based on minimizing the event shape N-jettiness. Because N-jettiness partitions every event into N jet regions and a beam region, XCone is an exclusive jet algorithm that always returns a fixed number of jets. We use a new "conical geometric" measure for which well-separated jets are bounded by circles of radius R in the rapidity-azimuth plane, while overlapping jet regions automatically form nearest-neighbor "clover jets". This avoids the split/merge criteria needed in inclusive cone algorithms. A key feature of XCone is that it smoothly transitions between the resolved regime where the N signal jets of interest are well separated and the boosted regime where they overlap. The returned value of N-jettiness also provides a quality criterion of how N-jet-like the event looks. We also discuss the N-jettiness factorization theorems that occur for various jet measures, which can be used to compute the associated exclusive N-jet cross sections. In a companion paper, the physics potential of XCone is demonstrated using the examples of dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs.

   hep-phhep-exJHEP(2015)·88 citations
6. 06*

   Resolving Boosted Jets with XCone

   Jesse Thaler🇺🇸 · Thomas F. Wilkason🇺🇸

   We show how the recently proposed XCone jet algorithm smoothly interpolates between resolved and boosted kinematics. When using standard jet algorithms to reconstruct the decays of hadronic resonances like top quarks and Higgs bosons, one typically needs separate analysis strategies to handle the resolved regime of well-separated jets and the boosted regime of fat jets with substructure. XCone, by contrast, is an exclusive cone jet algorithm that always returns a fixed number of jets, so jet regions remain resolved even when (sub)jets are overlapping in the boosted regime. In this paper, we perform three LHC case studies---dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs---that demonstrate the physics applications of XCone over a wide kinematic range.

   hep-phhep-exJHEP(2015)·39 citations
7. 07*

   Searching for Displaced Higgs Decays

   Csaba Csaki🇺🇸 · Eric Kuflik🇺🇸 · Salvator Lombardo🇺🇸 · Oren Slone🇮🇱

   We study a simplified model of the SM Higgs boson decaying to a degenerate pair of scalars which travel a macroscopic distance before decaying to SM particles. This is the leading signal for many well-motivated solutions to the hierarchy problem that do not propose additional light colored particles. Bounds for displaced Higgs decays below $10$ cm are found by recasting existing tracker searches from Run I. New tracker search strategies, sensitive to the characteristics of these models and similar decays, are proposed with sensitivities projected for Run II at $\sqrt{s}=13$ TeV. With 20 fb${}^{-1}$ of data, we find that Higgs branching ratios down to $7\times 10^{-4}$ can be probed for centimeter decay lengths.

   hep-phPRD(2015)·70 citations
8. 08*

   Constraints on tensor and scalar couplings from $B\to K\bar{\mu }\mu$ and $B_s\to \bar{\mu }\mu$

   Frederik Beaujean🇩🇪 · Christoph Bobeth🇩🇪 · Stephan Jahn🇩🇪

   The angular distribution of $B\to K\bar{\ell }\ell$ ($\ell =e,\mu ,\tau$) depends on two parameters, the lepton forward-backward asymmetry, $A_{\mathrm{FB}}^{\ell }$, and the flat term, $F_H^{\ell }$. Both are strongly suppressed in the standard model and constitute sensitive probes of tensor and scalar contributions. We use the latest experimental results for $\ell =\mu$ in combination with the branching ratio of $B_s\to \bar{\mu }\mu$ to derive the strongest model-independent bounds on tensor and scalar effective couplings to date. The measurement of $F_H^{\mu }$ provides a complementary constraint to that of the branching ratio of $B_s\to \bar{\mu }\mu$ and allows us---for the first time---to constrain all complex-valued (pseudo-)scalar couplings and their chirality-flipped counterparts in one fit. Based on Bayesian fits of various scenarios, we find that our bounds even become tighter when vector couplings are allowed to deviate from the standard model and that specific combinations of angular observables in $B\to K^{\ast }$ are still allowed to be up to two orders of magnitude larger than in the standard model, which would place them in the region of LHCb's sensitivity.

   hep-phhep-exhep-latEPJC(2015)·55 citations
9. 09*

   Higgs production in bottom-quark fusion in a matched scheme

   Stefano Forte🇮🇹 · Davide Napoletano🇬🇧 · Maria Ubiali🇬🇧

   We compute the total cross-section for Higgs boson production in bottom-quark fusion using the so-called FONLL method for the matching of a scheme in which the $b$-quark is treated as a massless parton to that in which it is treated as a massive final-state particle. We discuss the general framework for the application of the FONLL method to this process, and then we present explicit expressions for the case in which the next-to-next-to-leading-log five-flavor scheme result is combined with the leading-order $\mathcal{O}({\alpha }_s^2)$ four-flavor scheme computation. We compare our results in this case to the four-and five-flavor scheme computations, and to the so-called Santander matching.

   hep-phPLB(2015)·111 citations
10. 10*

    Majorana neutrino decay in an Effective Approach

    Lucia Duarte🇺🇾 · Javier Peressutti🇦🇷 · O.A. Sampayo🇦🇷

    The search strategy or the finding of new effects for heavy neutrinos often relies on their different decay channels to detectable particles. In particular in this work we study the decay of a Majorana neutrino with interactions obtained from an effective general theory modeling new physics at the scale $\Lambda$. The results obtained are general because they are based in an effective theory and not in specific models. We are interested in relatively light heavy Majorana neutrinos, with masses lower than the $W$ mass ($m_N<m_W$). This mass range simplifies the study by reducing the possible decay modes. Moreover, we found that for $\Lambda \sim 1$ T$e$V, the neutrino plus photon channel could give explanation to different observations: we analyze the potentiality of the studied interactions to explain some neutrino-related problems like the MiniBooNE and SHALON anomalies. We show in different figures the dominant branching ratios and the decay length of the Majorana neutrino in this approach. This kind of heavy neutral leptons could be searched for in the LHC with the use of displaced vertices techniques. \

    hep-phPRD(2015)·49 citations
11. 11*

    Fermionic extensions of the Standard Model in light of the Higgs couplings

    Nicolas Bizot (L2C, Montpellier)🇫🇷 · Michele Frigerio (L2C, Montpellier)🇫🇷

    As the Higgs boson properties settle, the constraints on the Standard Model extensions tighten. We consider all possible new fermions that can couple to the Higgs, inspecting sets of up to four chiral multiplets. We confront them with direct collider searches, electroweak precision tests, and current knowledge of the Higgs couplings. The focus is on scenarios that may depart from the decoupling limit of very large masses and vanishing mixing, as they offer the best prospects for detection. We identify exotic chiral families that may receive a mass from the Higgs only, still in agreement with the $h\gamma \gamma$ signal strength. A mixing $\theta$ between the Standard Model and non-chiral fermions induces order ${\theta }^2$ deviations in the Higgs couplings. The mixing can be as large as $\theta \sim 0.5$ in case of custodial protection of the $Z$ couplings or accidental cancellation in the oblique parameters. We also notice some intriguing effects for much smaller values of $\theta$, especially in the lepton sector. Our survey includes a number of unconventional pairs of vector-like and Majorana fermions coupled through the Higgs, that may induce order one corrections to the Higgs radiative couplings. We single out the regions of parameters where $h\gamma \gamma$ and $hgg$ are unaffected, while the $h\gamma Z$ signal strength is significantly modified, turning a few times larger than in the Standard Model in two cases. The second run of the LHC will effectively test most of these scenarios.

    hep-phhep-exJHEP(2016)·61 citations
12. 12*

    Inert Doublet Model in light of LHC Run I and astrophysical data

    Agnieszka Ilnicka🇨🇭 · Maria Krawczyk🇵🇱 · Tania Robens🇩🇪

    We discuss the parameter space of the Inert Doublet Model, a two Higgs doublet model with a dark matter candidate. An extensive set of theoretical and experimental constraints on this model is considered, where both collider as well as astroparticle data limits, the latter in the form of dark matter relic density as well as direct detection, are taken into account. We discuss the effects of these constraints on the parameter space of the model. In particular, we do not require the IDM to provide the full dark matter content of the universe, which opens up additional regions in the parameter space accessible at collider experiments. The combination of all constraints leads to a relatively strong mass degeneracy in the dark scalar sector for masses < 200 GeV, and to a minimal scale ~ 45 GeV for the dark scalar masses. We also observe a stringent mass hierarchy MH > MA. We propose benchmark points and benchmark planes for dark scalar pair-production for the current LHC run being in compliance with all theoretical as well as experimental bounds.

    hep-phPRD(2016)·192 citations
13. 13*

    Neutrino properties from ultra-high energy cosmic neutrinos

    Yanqi Huang🇨🇳 · Bo-Qiang Ma🇨🇳

    Neutrino properties can be constrained by the detection of ultra-high energy cosmic neutrinos (UHECNs). By using the updated global fitting results of neutrino mixing parameters, we present predictions on the neutrino flavor ratios at the Earth from three possibly astrophysical sources. Comparing with the latest IceCube data, we find that the normal hierarchy (NH) and inverted hierarchy (IH) cases from the initial ratios ${\varphi }_{{\nu }_e}^0:{\varphi }_{{\nu }_{\mu }}^0:{\varphi }_{{\nu }_{\tau }}^0=$1:2:0 and 0:1:0 are compatible with the data in the standard neutrino oscillation scenario. We also examine the neutrino flavor ratios in a neutrino decay scenario beyond the standard model, and introduce the special case that two mass eigenstates of neutrinos, i.e., ${\nu }_1$ and ${\nu }_2$, are degenerated. We find that the IH case and the degenerate NH case from the 1:2:0 and 0:1:0 sources are still permissible with the IceCube data within the $3\sigma$ error range. The general constraints only rely on the neutrino mixing and oscillation framework are also discussed.

    hep-phThe Universe(2015)·9 citations
14. 14*

    Lepton flavour violation in RS models with a brane- or nearly brane-localized Higgs

    M. Beneke (TUM)🇩🇪 · P. Moch (TUM)🇩🇪 · J. Rohrwild (Oxford U.)🇬🇧

    We perform a comprehensive study of charged lepton flavour violation in Randall-Sundrum (RS) models in a fully 5D quantum-field-theoretical framework. We consider the RS model with minimal field content and a "custodially protected" extension as well as three implementations of the IR-brane localized Higgs field, including the non-decoupling effect of the Kaluza-Klein (KK) excitations of a narrow bulk Higgs. Our calculation provides the first complete result for the flavour-violating electromagnetic dipole operator in Randall-Sundrum models. It contains three contributions with different dependence on the magnitude of the anarchic 5D Yukawa matrix, which can all be important in certain parameter regions. We study the typical range for the branching fractions of mu -> e gamma, mu -> 3e, mu N -> e N as well as tau -> mu gamma, tau -> 3 mu and the electron electric dipole moment by a numerical scan in both the minimal and the custodial RS model. The combination of mu -> e gamma and mu N -> e N currently provides the most stringent constraint on the parameter space of the model. A typical lower limit on the KK scale T is around 2 TeV in the minimal model (up to 4 TeV in the bulk Higgs case with large Yukawa couplings), and around 4 TeV in the custodially protected model, which corresponds to a mass of about 10 TeV for the first KK excitations, far beyond the lower limit from the non-observation of direct production at the LHC.

    hep-phNPB(2016)·22 citations
15. 15*

    Inflationary Potentials from the Exact Renormalisation Group

    Sašo Grozdanov🇳🇱 · David Kraljic🇬🇧 · Eirik Eik Svanes🇫🇷

    We show that an inflationary slow-roll potential can be derived as an IR limit of the non-perturbative exact renormalisation group equation for a scalar field within the mean-field approximation. The result follows without having to specify a Lagrangian for the UV theory at the Planck scale. We assume that the theory contains a scalar mode with suppressed coupling to other UV fields, and that higher derivative couplings are suppressed. The resulting effective potential gives rise to slow-roll inflation, which is fully consistent with the recent observations. As an example of how the proposed renormalisation group procedure works, we perform an explicit calculation in the ${\varphi }^4$ theory.

    ↳ hep-thastro-ph.COhep-phNPB(2016)·4 citations
16. 16*

    Experimental Conditions for Determination of the Neutrino Mass Hierarchy with Reactor Antineutrinos

    M. Y. Pac🇰🇷

    This article reports the optimized experimental requirements to determine neutrino mass hierarchy using electron antineutrinos (${\bar{\nu }}_e$) generated in a nuclear reactor. The features of the neutrino mass hierarchy can be extracted from the $|\Delta m_{31}^2|$ and $|\Delta m_{32}^2|$ oscillations by applying the Fourier sine and cosine transform to the $L/E$ spectrum. To determine the neutrino mass hierarchy above 90\% probability, the requirements on the energy resolution as a function of the baseline are studied at $\sin 2{\theta }_{13}=0.1$. If the energy resolution of the neutrino detector is less than $0.04/\sqrt{E_{\nu }}$ and the determination probability obtained from Bayes' theorem is above 90\%, the detector needs to be located around 48--53 km from the reactor(s) to measure the energy spectrum of ${\bar{\nu }}_e$. These results will be helpful for setting up an experiment to determine the neutrino mass hierarchy, which is an important problem in neutrino physics.

    ↳ hep-exhep-phphysics.data-anphysics.ins-detNPB(2016)·6 citations
17. 17*

    Hindered M1 Radiative Decay of ${\rm Y}(2S)$ from Lattice NRQCD

    Ciaran Hughes🇬🇧 · Rachel J. Dowdall🇬🇧 · Christine T. H. Davies🇬🇧 · Ronald R. Horgan🇬🇧 · Georg von Hippel🇩🇪 · Matthew Wingate🇬🇧

    We present a calculation of the hindered M$1$ ${\rm Y}(2S)\to {\eta }_b(1S)\gamma$ decay rate using lattice non-relativistic QCD. The calculation includes spin-dependent relativistic corrections to the NRQCD action through $\mathcal{O}(v^6)$ in the quark's relative velocity, relativistic corrections to the leading order current which mediates the transition through the quark's magnetic moment, radiative corrections to the leading spin-magnetic coupling and for the first time a full error budget. We also use gluon field ensembles at multiple lattice spacing values, all of which include $u$, $d$, $s$ and $c$ quark vacuum polarisation. Our result for the branching fraction is $\mathcal{B}({\rm Y}(2S)\to {\eta }_b(1S)\gamma )=5.4(1.8)\times 10^{-4}$, which agrees with the current experimental value.

    ↳ hep-lathep-phPRD(2015)·19 citations
18. 18*

    Can Tsallis distribution fit all the particle spectra produced at RHIC and LHC?

    H. Zheng🇮🇹 · Lilin Zhu🇨🇳

    The Tsallis distribution has been tested to fit the all particle spectra at mid-rapidity from central events produced in d+Au, Cu+Cu, Au+Au collisions at RHIC and p+Pb, Pb+Pb collisions at LHC. Even though there are strong medium effects in Cu+Cu and Au+Au collisions, the results show that the Tsallis distribution can be used to fit most of particle spectra in the collisions studied except in Au+Au collisions where some deviations are seen for proton and $\Lambda$ at low $p_T$. In addition, as the Tsallis distribution can only fit part of the particle spectra produced in Pb+Pb collisions where $p_T$ is up to 20 GeV/c, a new formula with one more fitting degree of freedom is proposed in order to reproduce the entire $p_T$ region.

    ↳ nucl-thhep-phAdv.High Energy Phys.(2015)·60 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.