Fri·Mar 4, 2016Friday·March 4, 2016

1. 01*

   Thermo-magnetic properties of the strong coupling in the local Nambu--Jona-Lasinio model

   Alejandro Ayala🇲🇽 · C. A. Dominguez🇿🇦 · L. A. Hernandez🇿🇦 · M. Loewe🇿🇦 · Alfredo Raya🇲🇽 · J. C. Rojas🇨🇱 · C. Villavicencio🇨🇱

   We study the thermo-magnetic properties of the strong coupling constant G and quark mass M entering the Nambu-Jona-Lasinio model. For this purpose, we compute the quark condensate and compare it to lattice QCD (LQCD) results to extract the behavior of G and M as functions of the magnetic field strength and temperature. We find that at zero temperature, where the LQCD condensate is found to monotonically increase with the field strength, M also increases whereas G remains approximately constant. However, for temperatures above the chiral/deconfinement phase transitions, where the LQCD condensate is found to monotonically decrease with increasing field, M and G also decrease monotonically. For finite temperatures, below the transition temperature, we find that both G and M initially grow and then decrease with increasing field strength. To study possible consequences of the extracted temperature and magnetic field dependence of G and M, we compute the pressure and compare to LQCD results, finding an excellent qualitative agreement. In particular, we show that the transverse pressure, as a function of the field strength, is always negative for temperatures below the transition temperature whereas it starts off being positive and then becomes negative for temperatures above the transition temperature, also in agreement with LQCD results. We also show that for the longitudinal pressure to agree with LQCD calculations, the system should be described as a diamagnet. We argue that the turnover of M and G as functions of temperature and field strength is a key element that drives the behavior of the quark condensate going across the transition temperature and provides clues for a better understanding of the inverse magnetic catalysis phenomenon.

   hep-phhep-latnucl-thPRD(2016)·53 citations
2. 02*

   On the anomalies in the latest LHCb data

   T. Hurth🇩🇪 · F. Mahmoudi🇫🇷 · S. Neshatpour🇮🇷

   Depending on the assumptions on the power corrections to the exclusive b -> s l+ l- decays, the latest data of the LHCb collaboration - based on the 3 fb^-1 data set and on two different experimental analysis methods - still shows some tensions with the SM predictions. We present a detailed analysis of the theoretical inputs and various global fits to all the available b -> s l+ l- data. This constitutes the first global analysis of the new data of the LHCb collaboration based on the hypothesis that these tensions can be at least partially explained by new physics contributions. In our model-independent analysis we present one-, two-, four-, and also five-dimensional global fits in the space of Wilson coefficients to all available b -> s l+ l- data. We also compare the two different experimental LHCb analyses of the angular observables in B -> K* mu+ mu-. We explicitly analyse the dependence of our results on the assumptions about power corrections, but also on the errors present in the form factor calculations. Moreover, based on our new global fits we present predictions for ratios of observables which may show a sign of lepton non-universality. Their measurements would crosscheck the LHCb result on the ratio R_K = BR(B+ -> K+ mu+ mu-) / BR(B+ -> K+ e+ e-) in the low-q^2 region which deviates from the SM prediction by 2.6 sigma.

   hep-phNPB(2016)·200 citations
3. 03*

   Amplitude analysis of $\bar{K}N$ scattering

   Cesar Fernandez-Ramirez🇲🇽

   We present the results of a coupled-channel model for $\bar{K}N$ scattering in the resonance region. The model fulfills unitarity, has the correct analytical properties for the amplitudes and the partial waves have the right threshold behavior. The parameters of the model have been established by fitting single-energy partial waves up to $J=7/2$ and up to 2.15 GeV of center-of-mass energy. The ${\Lambda }^{\ast }$ and ${\Sigma }^{\ast }$ spectra has been obtained, providing a comprehensive picture of the $S=-1$ hyperon spectrum. We use the structure of the hyperon spectrum and Regge phenomenology to gain insight on the nature of the $\Lambda (1405)$ resonances.

   hep-phnucl-thJ.Phys.Conf.Ser.(2016)·4 citations
4. 04*

   Heavy neutrino impact on the triple Higgs coupling

   Julien Baglio🇩🇪 · Cédric Weiland🇬🇧

   We present the first calculation of the one-loop corrections to the triple Higgs coupling in the framework of a simplified 3+1 Dirac neutrino model, that is three light neutrinos plus one heavy neutrino embedded in the Standard Model (SM). The triple Higgs coupling is a key parameter of the scalar potential triggering the electroweak symmetry-breaking mechanism in the SM. The impact of the heavy neutrino can be as large as $+20\%$ to $+30\%$ for parameter points allowed by the current experimental constraints depending on the tightness of the perturbative bound. This can be probed at the high-luminosity LHC, at future electron-positron colliders and at the Future Circular Collider in hadron-hadron mode, an envisioned 100 TeV $pp$ machine. Our calculation, being done in the mass basis, can be extended to any model using the neutrino portal. In addition, the effects that we have calculated are expected to be enhanced if additional heavy fermions with large Yukawa couplings are included, as in low-scale seesaw mechanisms.

   hep-phhep-exPRD(2016)·20 citations
5. 05*

   Diphoton and Diboson Probes of Fermiophobic Higgs Bosons at the LHC

   Antonio Delgado🇺🇸 · Mateo Garcia-Pepin🇪🇸 · Mariano Quiros🇪🇸 · Jose Santiago🇪🇸 · Roberto Vega-Morales🇪🇸

   Extensions of the Standard Model Higgs sector with electroweak charged scalars can possess exotic `Higgs' bosons with vanishing or suppressed couplings to Standard Model fermions. These `fermiophobic' scalars, which cannot be produced via gluon fusion, are constrained by LHC measurements of the 125 GeV Higgs boson to have a small vacuum expectation value. This implies that vector boson fusion and associated vector boson production are in general suppressed rendering conventional Higgs searches insensitive. However, Drell-Yan Higgs pair production, which is not present in the SM, can be sizeable even in the limit of vanishing exotic Higgs vacuum expectation value. We utilize this to show that diphoton searches at 8 TeV LHC already rule out a large class of neutral fermiophobic Higgs bosons below around 110 GeV. This includes fermiophobic scalars found in two Higgs doublet as well as Higgs triplet and Georgi-Machacek type models. Our results extend the only relevant limit on fermiophobic Higgs bosons obtained by a recent CDF analysis of $4\gamma +X$ Tevatron data. Furthermore, diphoton limits are independent of the decay of the second Higgs boson and thus apply even for degenerate masses in contrast to the CDF search. We also find that if the fermiophobic Higgs has very enhanced couplings to photons, masses as large as $\sim 150$ GeV can be ruled out while if these couplings are somehow highly suppressed, masses below $\sim 90$ GeV can still be ruled out. Finally, we show that $WW$ and $ZZ$ diboson searches may serve as complementary probes for masses above the diphoton limit up to $\sim 250$ GeV and discuss prospects at 13 TeV LHC.

   hep-phhep-exJHEP(2016)·34 citations
6. 06*

   Medium-induced gluon radiation in hard forward parton scattering in the saturation formalism

   Stéphane Munier🇫🇷 · Stéphane Peigné🇫🇷 · Elena Petreska🇫🇷

   We derive the medium-induced, coherent gluon radiation spectrum associated with the hard forward scattering of an energetic parton off a nucleus, in the saturation formalism and within the Gaussian approximation for the relevant correlators of Wilson lines. The calculation reproduces the simple expression for the spectrum previously obtained in the opacity expansion formalism, and rigorously specifies its validity range. The connection between the calculations in the opacity expansion and saturation formalisms is made apparent. This study may serve as a first step in order to implement consistently induced coherent energy loss and gluon shadowing in `saturation-based models' of hadron nuclear suppression in proton-nucleus collisions.

   hep-phPRD(2017)·13 citations
7. 07*

   Probe of the Anomalous Quartic Couplings with Beam Polarization at the CLIC

   A. Senol🇹🇷 · M. Köksal🇹🇷 · S. C. İnan🇹🇷

   We have investigated the anomalous quartic couplings defined by the dimension-8 operators in semileptonic decay channel of the $e^{+}{e}^{-}\to {\nu }_e{W}^{-}{W}^{+}{\bar{\nu }}_e$ process for unpolarized and polarized electron (positron) beam at the Compact Linear Collider. We give the $95\%$ confidence level bounds on anomalous $\frac{f_{S0}}{{\Lambda }^4}$, $\frac{f_{S1}}{{\Lambda }^4}$ and $\frac{f_{T0}}{{\Lambda }^4}$ couplings for various values of the integrated luminosities and center-of-mass energies. The best sensitivities obtained on anomalous $\frac{f_{S0}}{{\Lambda }^4}$, $\frac{f_{S1}}{{\Lambda }^4}$ and $\frac{f_{T0}}{{\Lambda }^4}$ couplings through the process $e^{+}{e}^{-}\to {\nu }_e{W}^{-}{W}^{+}{\bar{\nu }}_e$ with beam polarization at $\sqrt{s}=3$ TeV and an integrated luminosity of $L_{int}=2000$ fb${}^{-1}$ are $[-4.05;3.67]\times 10^{-12}$ GeV${}^{-4}$, $[-3.08;2.12]\times 10^{-12}$ GeV${}^{-4}$, $[-1.98;0.64]\times 10^{-13}$ GeV${}^{-4}$, which show improvement over the current bounds.

   hep-phAdv.High Energy Phys.(2017)·11 citations
8. 08*

   Effect of the $2p2h$ cross-section uncertainties on an analysis of neutrino oscillations

   Artur M. Ankowski🇺🇸 · Omar Benhar🇮🇹 · Camillo Mariani🇺🇸 · Erica Vagnoni🇮🇹

   We report the results of a study aimed at quantifying the impact on the oscillation analysis of the uncertainties associated with the description of the neutrino-nucleus cross section in the two-particle--two-hole sector. The results of our calculations, based on the kinematic method of energy reconstruction and carried out comparing two data-driven approaches, show that the existing discrepancies in the neutrino cross sections have a sizable effect on the extracted oscillation parameters, particularly in the antineutrino channel.

   hep-phhep-exnucl-thPRD(2016)·29 citations
9. 09*

   Backreaction Effects on Nonequilibrium Spectral Function

   Sebastian Mendizabal🇨🇱 · Juan Cristobal Rojas🇨🇱

   We show how to compute the spectral function for a scalar theory in two different scenarios: one which disregards back-reaction i.e. the response of the environment to the external particle, and the other one where back-reaction is considered. The calculation was performed using the Kadanoff-Baym equation through the Keldysh formalism. When back-reaction is neglected, the spectral function is equal to the equilibrium one, which can be represented as a Breit-Wigner distribution. When back-reaction is introduced we observed a damping in the spectral function of the thermal bath. Such behavior modifies the damping rate for particles created within the bath. This certainly implies phenomenological consequences right after the Big-Bang, when the primordial bath was created.

   hep-phgr-qchep-thInt.J.Mod.Phys.A(2017)·2 citations
10. 10*

    $X(5568)$ and and its partner states

    Yan-Rui Liu🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    Stimulated by the recent observation of the $X(5568)$, we study the $X(5568)$ and its partners under the tetraquark scenario. In the framework of the color-magnetic interaction, we estimate the masses of the partner states of the $X(5568)$ and discuss their decay pattern, which provide valuable information on the future experimental search of these states.

    hep-phhep-exhep-latnucl-thPRD(2016)·64 citations
11. 11*

    Production of massless bottom jets in ppbar and pp collisions at next-to-leading order of QCD

    Isabella Bierenbaum🇩🇪 · Gustav Kramer🇩🇪

    We present predictions for the inclusive production of bottom jets in proton-antiproton collisions at 1.96 TeV and proton-proton collisions at 7 TeV. The bottom quark is considered massless. In this scheme, we find that at small transverse momentum (p_T) the ratio of the next-to-leading order to the leading-order cross section (K factor) is smaller than one. It increases with increasing p_T and approaches one at larger p_T at a value depending essentially on the choice of the renormalization scale. Adding non-perturbative corrections obtained from PYTHIA Monte Carlo calculations leads to reasonable agreement with experimental b-jet cross sections obtained by the CDF and the CMS collaborations.

    hep-phhep-exInt.J.Mod.Phys.A(2016)·1 citation
12. 12*

    Off-shell single-top production at NLO matched to parton showers

    Rikkert Frederix🇩🇪 · Stefano Frixione🇮🇹 · Andrew S. Papanastasiou🇬🇧 · Stefan Prestel🇺🇸 · Paolo Torrielli🇮🇹

    We study the hadroproduction of a $Wb$ pair in association with a light jet, focusing on the dominant $t$-channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the HERWIG6 and PYTHIA8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell $t$-channel single-top production. We formulate our approach so that it can be applied to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.

    hep-phJHEP(2016)·82 citations
13. 13*

    Constructing Scalar-Photon Three Point Vertex in Massless Quenched Scalar QED

    L. Albino Fernandez-Rangel🇲🇽 · A. Bashir🇲🇽 · L.X. Gutierrez-Guerrero🇲🇽 · Y. Concha-Sanchez🇲🇽

    Non perturbative studies of Schwinger-Dyson equations (SDEs) require their infnite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the three point scalar-photon vertex can be expressed in terms of only two independent form factors, a longitudinal and a transverse one. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green-Takahashi identity (WFGTI), while the transverse vertex remains undetermined. In massless quenched sQED, we construct the transverse part of the non perturbative scalar-photon vertex. This construction (i) ensures multiplicative renormalizability (MR) of the scalar propagator in keeping with the Landau-Khalatnikov-Fradkin transformations (LKFTs), (ii) has the same transformation properties as the bare vertex under charge conjugation, parity and time reversal, (iii) has no kinematic singularities and (iv) reproduces one loop asymptotic result in the weak coupling regime of the theory.

    hep-phhep-thPRD(2016)·13 citations
14. 14*

    The impact of additional scalar bosons at the LHC

    Mukesh Kumar🇿🇦 · Stefan von Buddenbrock🇿🇦 · Nabarun Chakrabarty🇮🇳 · Alan S. Cornell🇿🇦 · Deepak Kar🇿🇦 · Tanumoy Mandal🇸🇪 · Bruce Mellado🇿🇦 · Biswarup Mukhopadhyaya🇮🇳 · Robert Reed🇿🇦

    In this study we consider an effective model by introducing two hypothetical real scalars, $H$ and $\chi$ - a dark matter candidate, where the masses of these scalars are $2m_h<m_H<2m_t$ and $m_{\chi }\approx m_h/2$ with $m_h$ and $m_t$ being the Standard Model Higgs boson and top quark masses respectively. A distortion in the transverse momentum distributions of $h$ in the intermediate region of the spectrum through the processes $pp\to H\to h\chi \chi$ could be observed in this model. An additional scalar, $S$, has been postulated to explain large $H\to h\chi \chi$ branching ratios, assuming $m_h\lesssim m_S\lesssim m_H-m_h$ and $m_S>2m_{\chi }$. Furthermore, a scenario of a two Higgs doublet model (2HDM) is introduced and a detailed proposal at the present energies of the Large Hadron Collider to study the extra CP-even ($h,H$), CP-odd ($A$) and charged ($H^{\pm }$) scalars has been pursued. With possible phenomenological implications, all possible spectra and decay modes for these scalars are discussed. Based on the mass spectrum of $H,A$ and $H^{\pm }$, the production of multi-leptons and $Z$+jets+missing-energy events are predicted. A specific, Type-II 2HDM model is discussed in detail.

    hep-phhep-exJ.Phys.Conf.Ser.(2017)·14 citations
15. 15*

    On quasidegeneracy of Majorana neutrinos and the observed pattern of Leptonic mixing

    M. N. Rebelo🇵🇹

    We relate the observed pattern of leptonic mixing to the quaidegeneracy of three Majorana neutrinos. We show how lifting the degeneracy may lead to the measured value of $|U_{13}|$ and to sizeable CP violation of Dirac-type. We show some of the correlations obtained among physical observables, starting from some of the most interesting schemes proposed in the literature.

    hep-ph0 citations
16. 16*

    Forecasting the Socio-Economic Impact of the Large Hadron Collider: a Cost-Benefit Analysis to 2025 and Beyond

    Massimo Florio🇮🇹 · Stefano Forte🇮🇹 · Emanuela Sirtori🇮🇹

    In this paper we develop a cost-benefit analysis of a major research infrastructure, the Large Hadron Collider (LHC), the highest-energy accelerator in the world, currently operating at CERN. We show that the evaluation of benefits can be made quantitative by estimating their welfare effects on different types of agents. Four classes of direct benefits are identified, according to the main social groups involved: (a) scientists; (b) students and young researchers; (c) firms in the procurement chain and other organizations; (d) the general public, including onsite and website visitors and other media users. These benefits are respectively related to the knowledge output of scientists; human capital formation; technological spillovers; and direct cultural effects for the general public. Welfare effects for taxpayers can also be estimated by the contingent valuation of the willingness to pay for a pure public good for which there is no specific direct use (i.e., as non-use value). Using a Monte Carlo approach, we estimate the conditional probability distribution of costs and benefits for the LHC from 1993 until its planned decommissioning in 2025, assuming a range of values for some critical stochastic variables. We conservatively estimate that there is around a 90\% probability that benefits exceed costs, with an expected net present value of about 2.9 billion euro, not considering the unpredictable applications of scientific discovery.

    ↳ physics.soc-phhep-exhep-phphysics.acc-phTechn. For. and Soc. Change 112 (2016) 38·20 citations
17. 17*

    Nucleon Resonance Physics

    Volker D. Burkert🇺🇸

    Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $\Delta$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^2>1.5Ge{V}^2$. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.

    ↳ nucl-exhep-lathep-phnucl-thFew Body Syst.(2016)·17 citations
18. 18*

    Search for Gamma-ray Emission from Dark Matter Annihilation in the Small Magellanic Cloud with the Fermi Large Area Telescope

    Regina Caputo🇺🇸 · Matthew R. Buckley🇺🇸 · Pierrick Martin🇫🇷 · Eric Charles🇺🇸 · Alyson M. Brooks🇺🇸 · Alex Drlica-Wagner🇺🇸 · Jennifer M. Gaskins🇳🇱 · Matthew Wood🇺🇸

    The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy of the Milky Way and is only 60 kpc away. As a nearby, massive, and dense object with relatively low astrophysical backgrounds, it is a natural target for dark matter indirect detection searches. In this work, we use six years of Pass 8 data from the Fermi Large Area Telescope to search for gamma-ray signals of dark matter annihilation in the SMC. Using data-driven fits to the gamma-ray backgrounds, and a combination of N-body simulations and direct measurements of rotation curves to estimate the SMC DM density profile, we found that the SMC was well described by standard astrophysical sources, and no signal from dark matter annihilation was detected. We set conservative upper limits on the dark matter annihilation cross section. These constraints are in agreement with stronger constraints set by searches in the Large Magellanic Cloud and approach the canonical thermal relic cross section at dark matter masses lower than 10 GeV in the $b\bar{b}$ and ${\tau }^{+}{\tau }^{-}$ channels.

    ↳ astro-ph.HEhep-exhep-phPRD(2016)·43 citations
19. 19*

    A Theory of Ambulance Chasing

    Mihailo Backović🇧🇪

    Ambulance chasing is a common socio-scientific phenomenon in particle physics. I argue that despite the seeming complexity, it is possible to gain insight into both the qualitative and quantitative features of ambulance chasing dynamics. Compound-Poisson statistics suffices to accommodate the time evolution of the cumulative number of papers on a topic, where basic assumptions that the interest in the topic as well as the number of available ideas decrease with time appear to drive the time evolution. It follows that if the interest scales as an inverse power law in time, the cumulative number of papers on a topic is well described by a di-gamma function, with a distinct logarithmic behavior at large times. In cases where the interest decreases exponentially with time, the model predicts that the total number of papers on the topic will converge to a fixed value as time goes to infinity. I demonstrate that the two models are able to fit at least 9 specific instances of ambulance chasing in particle physics using only two free parameters. In case of the most recent ambulance chasing instance, the ATLAS {\gamma}{\gamma} excess, fits to the current data predict that the total number of papers on the topic will not exceed 310 papers by the June 1. 2016, and prior to the natural cut-off for the validity of the theory.

    ↳ physics.soc-phcs.DLhep-phphysics.data-an13 citations
20. 20*

    Violation of statistical isotropy and homogeneity in the 21-cm power spectrum

    Maresuke Shiraishi🇯🇵 · Julian B. Muñoz🇺🇸 · Marc Kamionkowski🇺🇸 · Alvise Raccanelli🇺🇸

    Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here, we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving upon the current CMB constraints by $\sim 2$ orders of magnitude for a dipolar asymmetry and by $\sim 1-3$ orders of magnitude for a quadrupolar asymmetry case.

    ↳ astro-ph.COgr-qchep-phPRD(2016)·35 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.