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CERN Document Server latest documents in Theoretical Physics (TH)enThu, 19 Jan 2017 12:54:59 GMTInvenio 1.1.3.1106-62468cds.support@cern.ch36014392125http://cds.cern.ch/img/site_logo_rss.pngCERN Document Server
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Exploring the squark flavour structure of the MSSM
http://cds.cern.ch/record/2241221
We present an extensive study of the MSSM parameter space allowing for general generation mixing in the squark sector. Employing an MCMC algorithm, we establish the parameter ranges which are allowed with respect to various experimental and theoretical constraints. Based on this analysis, we propose benchmark scenarios for future studies. Moreover, we discuss aspects of signatures at the LHC.De Causmaecker, KarenFuks, BenjaminHerrmann, BjörnMahmoudi, FarvahO'Leary, BenPorod, WernerSekmen, SezenStrobbe, NadjaWed, 11 Jan 2017 06:31:05 GMT2017-01-06LAPTH-CONF-065-16http://cds.cern.ch/record/224122106516Naturalness of asymptotically safe Higgs
http://cds.cern.ch/record/2241220
We introduce a model that contains a Higgs-like scalar with gauge, Yukawa and quartic interactions that enter a perturbative asymptotically safe regime at energies above a scale $\Lambda$. The model serves as a concrete example to test whether scalars masses unavoidably receive quantum correction of order $\Lambda$. The answer is that scalars can be naturally lighter. Although we do not have an answer to whether the Standard Model hypercharge coupling growth towards a Landau pole around $\Lambda \sim 10^{40}$ GeV can be tamed by non-perturbative asymptotic safety, our toy-SM shows that such a possibility is worth exploring. In fact, if successful, it might also offer an explanation for the unbearable lightness of the Higgs.Pelaggi, Giulio MariaSannino, FrancescoStrumia, AlessandroVigiani, ElenaWed, 11 Jan 2017 06:31:05 GMT2017-01-05CERN-TH-2017-001http://cds.cern.ch/record/22412202017001SUSY Meets Her Twin
http://cds.cern.ch/record/2236791
We investigate the general structure of mirror symmetry breaking in the Twin Higgs scenario. We show, using the IR effective theory, that a significant gain in fine tuning can be achieved if the symmetry is broken hardly. We emphasize that weakly coupled UV completions can naturally accommodate this scenario. We analyze SUSY UV completions and present a simple Twin SUSY model with a tuning of around 10% and colored superpartners as heavy as 2 TeV. The collider signatures of general Twin SUSY models are discussed with a focus on the extended Higgs sectors.Katz, AndreyMariotti, AlbertoPokorski, StefanRedigolo, DiegoZiegler, RobertFri, 02 Dec 2016 11:49:30 GMT25 Nov 2016arXiv:1611.08615http://cds.cern.ch/record/2236791['arXiv:1611.08615']arXiv:1611.08615LHC Signals from Cascade Decays of Warped Vector Resonances
http://cds.cern.ch/record/2236694
Recently (arXiv:1608.00526), a new framework for warped higher-dimensional compactifications with "bulk" standard model (SM) was proposed: in addition to the UV (Planck scale) and IR (a couple of TeV) branes, there is an intermediate brane, taken to be around 10 TeV. The SM matter and Higgs fields propagate from the UV brane down to this intermediate brane only, while gauge and gravity fields propagate in the entire bulk. Such a configuration renders the lightest gauge Kaluza-Klein (KK) states within LHC reach, simultaneously satisfying flavor and CP constraints. In addition, the usual leading decay modes of the lightest KK gauge bosons into top and Higgs bosons are suppressed. This effect permits erstwhile subdominant channels to become significant. These include flavor-universal decays to SM fermions and Higgs bosons, and a novel channel - decay to a radion and a SM gauge boson, followed by radion decay to a pair of SM gauge bosons. In this work, we first delineate the parameter space where the above mentioned cascade decay of gauge KK particles dominates, and thereby can be the discovery mode at the LHC. We then perform a detailed analysis of the LHC signals from this model, finding that 300/fb suffices for evidence of KK-gluon in tri-jet, jet + di-photon and jet + di-boson channels. However, KK photon in photon + di-jet, and KK-W in leptonic W + di-jet require 3000/fb. The crucial feature of this decay chain is a "double" resonance, i.e. 3-particle and 2-particle invariant mass peaks, corresponding to the KK gauge boson and the radion respectively.Agashe, Kaustubh SCollins, JackDu, PeizhiHong, SungwooKim, DoojinMishra, Rashmish K.Fri, 02 Dec 2016 11:44:28 GMT30 Nov 2016arXiv:1612.00047http://cds.cern.ch/record/2236694['arXiv:1612.00047']arXiv:1612.00047Determining the CP nature of spin-0 mediators in associated production of dark matter and $t \bar t$ pairs
http://cds.cern.ch/record/2236681
In the framework of spin-0 $s$-channel simplified models, we explore the possibility of assessing the structure of dark matter interactions through the associate production of dark matter and $t\bar{t}$ pairs. To this purpose, final states with two leptons are considered and the kinematic properties of the dilepton system is studied. We develop a realistic analysis strategy and provide a detailed evaluation of the achievable sensitivity for the dark matter signal assuming integrated luminosities of $300 \, {\rm fb}^{-1}$ and $3 \, {\rm ab}^{-1}$ at the 14 TeV LHC. Furthermore, upper limits on the mediator masses for which the two different CP hypotheses can be distinguished are derived. The obtained limits on the signal strengths are finally translated into constraints on the parameter space of two spin-0 simplified models including a scenario with an extended Higgs sector.Haisch, UlrichPani, PriscillaPolesello, GiacomoFri, 02 Dec 2016 11:44:23 GMT29 Nov 2016arXiv:1611.09841http://cds.cern.ch/record/2236681['arXiv:1611.09841']arXiv:1611.09841Phenomenological analysis of associated production of $Z^0+b$ in the $b \rightarrow J/\psi X$ decay channel at the LHC
http://cds.cern.ch/record/2236670
The ATLAS collaboration recently reported on the first observation of associated-production of a $Z^0$ boson with a $J/\psi$. We recently claimed that the corresponding yield of the {\it prompt} $J/\psi$ was dominated by double parton scatterings in the ATLAS acceptance with a somewhat small value of $\sigma_{\rm eff}$. We also found out that single parton scatterings were only dominant at large transverse momenta. We present here the first phenomenological analysis of another part of the ATLAS data sample, namely of a $Z^0$ boson plus a {\it non-prompt} $J/\psi$. Our study is performed at next-to-leading order in $\alpha_s$ and includes parton-shower effects via the {\sc\small MadGraph5_aMC@NLO} framework. We find out that the data, unlike the case of prompt $J/\psi+Z^0$, do not hint at significant DPS contributions. Owing to the current experimental and theoretical uncertainties, there is still a room for these but with a lower limit of $\sigma_{\rm eff}$ close to 5 mb. We stress the importance of QCD corrections to account for the ATLAS data.Lansberg, Jean-PhilippeShao, Hua-ShengFri, 02 Dec 2016 11:44:21 GMT28 Nov 2016arXiv:1611.09303http://cds.cern.ch/record/2236670['arXiv:1611.09303']arXiv:1611.09303Stringy bounces and gradient instabilities
http://cds.cern.ch/record/2236545
Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.Giovannini, MassimoFri, 02 Dec 2016 11:42:16 GMT01 Dec 2016arXiv:1612.00346http://cds.cern.ch/record/2236545['arXiv:1612.00346']arXiv:1612.00346Constraints on violation of Lorentz invariance from atmospheric showers initiated by multi-TeV photons
http://cds.cern.ch/record/2236459
We discuss the effect of hypothetical violation of Lorentz invariance at high energies on the formation of atmospheric showers by very-high-energy gamma rays. In the scenario where Lorentz invariance violation leads to a decrease of the photon velocity with energy the formation of the showers is suppressed compared to the Lorentz invariant case. Absence of such suppression in the high-energy part of spectrum of the Crab nebula measured independently by HEGRA and H.E.S.S. collaborations is used to set lower bounds on the energy scale of Lorentz invariance violation. These bounds are competitive with the strongest existing constraints obtained from timing of variable astrophysical sources and the absorption of TeV photons on the extragalactic background light. They will be further improved by the next generation of multi-TeV gamma-ray observatories.Rubtsov, GrigorySatunin, PetrSibiryakov, SergeyFri, 02 Dec 2016 11:37:51 GMT30 Nov 2016arXiv:1611.10125http://cds.cern.ch/record/2236459['arXiv:1611.10125']arXiv:1611.10125Controlling quark mass determinations non-perturbatively in three-flavour QCD
http://cds.cern.ch/record/2234048
The determination of quark masses from lattice QCD simulations requires a non-perturbative renormalization procedure and subsequent scale evolution to high energies, where a conversion to the commonly used MS-bar scheme can be safely established. We present our results for the non-perturbative running of renormalized quark masses in Nf=3 QCD between the electroweak and a hadronic energy scale, where lattice simulations are at our disposal. Recent theoretical advances in combination with well-established techniques allows to follow the scale evolution to very high statistical accuracy, and full control of systematic effects.Campos, IsabelFritzsch, PatrickPena, CarlosPreti, DavidRamos, AlbertoVladikas, TassosMon, 21 Nov 2016 06:41:42 GMT18 Nov 2016arXiv:1611.06102http://cds.cern.ch/record/2234048['arXiv:1611.06102']arXiv:1611.06102The determination of $\alpha_s$ by the ALPHA collaboration
http://cds.cern.ch/record/2233843
We review the ALPHA collaboration strategy for obtaining the QCD coupling at high scale. In the three-flavor effective theory it avoids the use of perturbation theory at $\alpha > 0.2$ and at the same time has the physical scales small compared to the cutoff $1/a$ in all stages of the computation. The result $\Lambda_\overline{MS}^{(3)}=332(14)$~MeV is translated to $\alpha_\overline{MS}(m_Z)=0.1179(10)(2)$ by use of (high order) perturbative relations between the effective theory couplings at the charm and beauty quark "thresholds". The error of this perturbative step is discussed and estimated as $0.0002$.Bruno, MattiaDalla Brida, MattiaFritzsch, PatrickKorzec, TomaszRamos, AlbertoSchaefer, StefanSimma, HubertSint, StefanSommer, RainerSat, 19 Nov 2016 06:56:51 GMT17 Nov 2016arXiv:1611.05750http://cds.cern.ch/record/2233843['arXiv:1611.05750']arXiv:1611.05750Constraints on the CP-Violating MSSM
http://cds.cern.ch/record/2233449
We discuss the prospects for observing CP violation in the MSSM with six CP-violating phases, using a geometric approach to maximise CP-violating observables subject to the experimental upper bounds on electric dipole moments. We consider constraints from Higgs physics, flavour physics, the dark matter relic density and spin-independent scattering cross section with matter.Arbey, AEllis, JGodbole, R MMahmoudi, FThu, 17 Nov 2016 07:30:42 GMT15 Nov 2016arXiv:1611.05061http://cds.cern.ch/record/2233449['arXiv:1611.05061']arXiv:1611.05061Present Status of b -> s l+ l- Anomalies
http://cds.cern.ch/record/2233448
We discuss the observed deviations in b -> s l+ l- processes from the Standard Model predictions and present global fits for the New Physics description of these anomalies. We further investigate the stability of the global fits under different theoretical assumptions and suggest strategies and a number of observables to clear up the source of the anomalies.Mahmoudi, FHurth, TNeshatpour, SThu, 17 Nov 2016 07:30:40 GMT15 Nov 2016arXiv:1611.05060http://cds.cern.ch/record/2233448['arXiv:1611.05060']arXiv:1611.05060Massless Interacting Scalar Fields in de Sitter space
http://cds.cern.ch/record/2228768
We present a method to compute the two-point functions for an $O(N)$ scalar field model in de Sitter spacetime, avoiding the well known infrared problems for massless fields. The method is based on an exact treatment of the Euclidean zero modes and a perturbative one of the nonzero modes, and involves a partial resummation of the leading secular terms. This resummation, crucial to obtain a decay of the correlation functions, is implemented along with a double expansion in an effective coupling constant $\sqrt\lambda$ and in $1/N$. The results reduce to those known in the leading infrared approximation and coincide with the ones obtained directly in Lorentzian de Sitter spacetime in the large $N$ limit. The new method allows for a systematic calculation of higher order corrections both in $\sqrt\lambda$ and in $1/N$.Nacir, Diana LópezMazzitelli, Francisco DTrombetta, Leonardo GTue, 01 Nov 2016 06:47:05 GMT31 Oct 2016arXiv:1610.09943http://cds.cern.ch/record/2228768['arXiv:1610.09943']arXiv:1610.09943Likelihood Analysis of Supersymmetric SU(5) GUTs
http://cds.cern.ch/record/2228749
We perform a likelihood analysis of the constraints from accelerator experiments and astrophysical observations on supersymmetric (SUSY) models with SU(5) boundary conditions on soft SUSY-breaking parameters at the GUT scale. The parameter space of the models studied has 7 parameters: a universal gaugino mass $m_{1/2}$, distinct masses for the scalar partners of matter fermions in five- and ten-dimensional representations of SU(5), $m_5$ and $m_{10}$, and for the $\mathbf{5}$ and $\mathbf{\bar 5}$ Higgs representations $m_{H_u}$ and $m_{H_d}$, a universal trilinear soft SUSY-breaking parameter $A_0$, and the ratio of Higgs vevs $\tan \beta$. In addition to previous constraints from direct sparticle searches, low-energy and flavour observables, we incorporate constraints based on preliminary results from 13 TeV LHC searches for jets + MET events and long-lived particles, as well as the latest PandaX-II and LUX searches for direct Dark Matter detection. In addition to previously-identified mechanisms for bringing the supersymmetric relic density into the range allowed by cosmology, we identify a novel ${\tilde u_R}/{\tilde c_R} - \tilde{\chi}^0_1$ coannihilation mechanism that appears in the supersymmetric SU(5) GUT model and discuss the role of ${\tilde \nu_\tau}$ coannihilation. We find complementarity between the prospects for direct Dark Matter detection and SUSY searches at the LHC.Bagnaschi, ECosta, J.C.Sakurai, K.Borsato, M.Buchmueller, O.Cavanaugh, R.Chobanova, V.Citron, M.De Roeck, A.Dolan, M.J.Ellis, J.R.Flächer, H.Heinemeyer, S.Isidori, G.Lucio, M.Martínez Santos, D.Olive, K.A.Richards, A.de Vries, K.J.Weiglein, G.Tue, 01 Nov 2016 06:46:07 GMT31 Oct 2016arXiv:1610.10084http://cds.cern.ch/record/2228749['arXiv:1610.10084']arXiv:1610.10084D = 3 Unification of Curious Supergravities
http://cds.cern.ch/record/2228159
We consider the dimensional reduction to D = 3 of four maximal-rank supergravities which preserve minimal supersymmetry in D = 11, 7, 5 and 4. Such "curious" theories were investigated some time ago, and the four-dimensional one corresponds to an N = 1 supergravity with 7 chiral multiplets spanning the seven-disk manifold. Recently, this latter theory was considered to provide cosmological models for alpha-attractors, which are based on the disk geometry with possible restrictions on the parameter alpha. A unified picture emerges in D = 3, where the Ehlers group of General Relativity merges with the S-, T- and U- dualities of the D = 4 parent theories.Duff, M.J.Ferrara, S.Marrani, A.Fri, 28 Oct 2016 05:41:22 GMT27 Oct 2016arXiv:1610.08800http://cds.cern.ch/record/2228159['arXiv:1610.08800']arXiv:1610.08800Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung
http://cds.cern.ch/record/2228150
We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.Mehtar-Tani, YacineTywoniuk, KonradFri, 28 Oct 2016 05:40:55 GMT27 Oct 2016arXiv:1610.08930http://cds.cern.ch/record/2228150['arXiv:1610.08930']arXiv:1610.08930Accurate initial conditions in mixed Dark Matter--Baryon simulations
http://cds.cern.ch/record/2228024
We quantify the error in the results of mixed baryon--dark-matter hydrodynamic simulations, stemming from outdated approximations for the generation of initial conditions. The error at redshift 0 in contemporary large simulations, is of the order of few to ten percent in the power spectra of baryons and dark matter, and their combined total-matter power spectrum. After describing how to properly assign initial displacements and peculiar velocities to multiple species, we review several approximations: (1) {using the total-matter power spectrum to compute displacements and peculiar velocities of both fluids}, (2) scaling the linear redshift-zero power spectrum back to the initial power spectrum using the Newtonian growth factor ignoring homogeneous radiation, (3) using longitudinal-gauge velocities with synchronous-gauge densities, and (4) ignoring the phase-difference in the Fourier modes for the offset baryon grid, relative to the dark-matter grid. Three of these approximations do not take into account that dark matter and baryons experience a scale-dependent growth after photon decoupling, which results in directions of velocity which are not the same as their direction of displacement. We compare the outcome of hydrodynamic simulations with these four approximations to our reference simulation, all setup with the same random seed and simulated using Gadget-III.Valkenburg, WesselVillaescusa-Navarro, FranciscoFri, 28 Oct 2016 05:38:16 GMT26 Oct 2016arXiv:1610.08501http://cds.cern.ch/record/2228024['arXiv:1610.08501']arXiv:1610.08501A Clockwork Theory
http://cds.cern.ch/record/2227514
The clockwork is a mechanism for generating light particles with exponentially suppressed interactions in theories which contain no small parameters at the fundamental level. We develop a general description of the clockwork mechanism valid for scalars, fermions, gauge bosons, and gravitons. This mechanism can be implemented with a discrete set of new fields or, in its continuum version, through an extra spatial dimension. In both cases the clockwork emerges as a useful tool for model-building applications. Notably, the continuum clockwork offers a solution to the Higgs naturalness problem, which turns out to be the same as in linear dilaton duals of Little String Theory. We also elucidate the similarities and differences of the continuum clockwork with large extra dimensions and warped spaces. All clockwork models, in the discrete and continuum, exhibit novel phenomenology with a distinctive spectrum of closely spaced resonances.Giudice, Gian FMcCullough, MatthewWed, 26 Oct 2016 06:39:43 GMT20 Oct 2016arXiv:1610.07962http://cds.cern.ch/record/2227514['arXiv:1610.07962']arXiv:1610.07962Spectator Higgs, large-scale gauge fields and the non-minimal coupling to gravity
http://cds.cern.ch/record/2227420
Even if the Higgs field does not affect the evolution of the background geometry, its massive inhomogeneities induce large-scale gauge fields whose energy density depends on the slow-roll parameters, on the effective scalar mass and, last but not least, on the dimensionless coupling to the space-time curvature. Since the non-Abelian gauge modes are screened, the non-minimal coupling to gravity predominantly affects the evolution of the hypercharge and electromagnetic fields. While in the case of minimal coupling the obtained constraints are immaterial, as soon as the coupling increases beyond one fourth the produced fields become overcritical. We chart the whole parameter space of this qualitatively new set of bounds. Whenever the limits on the curvature coupling are enforced, the magnetic field may still be partially relevant for large-scale magnetogenesis and exceed $10^{-20}$ G for the benchmark scale of the protogalactic collapse.Giovannini, MassimoWed, 26 Oct 2016 06:36:00 GMT25 Oct 2016arXiv:1610.07977http://cds.cern.ch/record/2227420['arXiv:1610.07977']arXiv:1610.07977Linearized supergravity with a dynamical preferred frame
http://cds.cern.ch/record/2227399
We study supersymmetric extension of the Einstein-aether gravitational model where local Lorentz invariance is broken down to the subgroup of spatial rotations by a vacuum expectation value of a timelike vector field. By restricting to the level of linear perturbations around Lorentz-violating vacuum and using the superfield formalism we construct the most general action invariant under the linearized supergravity transformations. We show that, unlike its non-supersymmetric counterpart, the model contains only a single free dimensionless parameter, besides the usual dimensionful gravitational coupling. This makes the model highly predictive. An analysis of the spectrum of physical excitations reveal superluminal velocity of gravitons. The latter property leads to the extension of the gravitational multiplet by additional fermonic and bosonic states with helicities $\pm 3/2$ and $\pm 1$. We outline the observational constraints on the model following from its low-energy phenomenology.Marakulin, ArthurSibiryakov, SergeyWed, 26 Oct 2016 06:35:56 GMT25 Oct 2016arXiv:1610.07805http://cds.cern.ch/record/2227399['arXiv:1610.07805']arXiv:1610.07805Exact $\nabla^4 R^4$ couplings and helicity supertraces
http://cds.cern.ch/record/2226938
In type II string theory compactified on a $d$-dimensional torus $T^d$ down to $D=10-d$ dimensions, the $R^4$ and $\nabla^4 R^4$ four-graviton couplings are known exactly, for all values of the moduli, in terms of certain Eisenstein series of the U-duality group $E_{d}(\mathbb{Z})$. In the limit where one circle in the torus becomes large, these couplings are expected to reduce to their counterpart in dimension $D+1$, plus threshold effects and exponentially suppressed corrections corresponding to BPS black holes in dimension $D+1$ whose worldline winds around the circle. By combining the weak coupling and large radius limits, we determine these exponentially suppressed corrections exactly, and demonstrate that the contributions of 1/4-BPS black holes to the $\nabla^4 R^4$ coupling are proportional to the appropriate helicity supertrace. Mathematically, our results provide the complete Fourier expansion of the next-to-minimal theta series of $E_{d+1}(\mathbb{Z})$ with respect to the maximal parabolic subgroup with Levi component $E_{d}$ for $d\leq 6$, and the complete Abelian part of the Fourier expansion of the same for $d=7$.Bossard, GuillaumePioline, BorisMon, 24 Oct 2016 05:21:43 GMT21 Oct 2016arXiv:1610.06693http://cds.cern.ch/record/2226938['arXiv:1610.06693']arXiv:1610.06693Science with the space-based interferometer LISA. IV: Probing inflation with gravitational waves
http://cds.cern.ch/record/2226671
We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during inflation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated inflationary scenarios beyond the irreducible vacuum tensor modes expected from any inflationary background.Bartolo, NicolaCaprini, ChiaraDomcke, ValerieFigueroa, Daniel GGarcia-Bellido, JuanGuzzetti, Maria ChiaraLiguori, MicheleMatarrese, SabinoPeloso, MarcoPetiteau, AntoineRicciardone, AngeloSakellariadou, MairiSorbo, LorenzoTasinato, GianmassimoSat, 22 Oct 2016 05:28:20 GMT20 Oct 2016arXiv:1610.06481http://cds.cern.ch/record/2226671['arXiv:1610.06481']arXiv:1610.06481Constraints on the trilinear Higgs coupling from vector boson fusion and associated Higgs production at the LHC
http://cds.cern.ch/record/2226225
We examine the constraints on the trilinear Higgs coupling $\lambda$ that originate from associated ($Vh$) and vector boson fusion (VBF) Higgs production in $pp$ collisions in the context of the Standard Model effective field theory. The 1-loop contributions to $pp \to V h$ and $pp \to jj h$ that stem from insertions of the dimension-6 operator $O_6 = - \lambda \left (H^\dagger H \right )^3$ are calculated and combined with the ${\cal O} (\lambda)$ corrections to the partial decay widths of the Higgs boson. Employing next-to-next-to-leading order QCD predictions, we analyse the sensitivity of current and forthcoming measurements of the signal strengths in $Vh$ and VBF Higgs production to changes in $\lambda$. We show that future LHC runs may be able to probe modifications of $\lambda$ with a sensitivity similar to the one that is expected to arise from determinations of double-Higgs production. The sensitivity of differential $Vh$ and VBF Higgs distributions to a modified $h^3$ coupling is also studied.Bizon, WojciechGorbahn, MartinHaisch, UlrichZanderighi, GiuliaThu, 20 Oct 2016 06:40:35 GMT18 Oct 2016arXiv:1610.05771http://cds.cern.ch/record/2226225['arXiv:1610.05771']arXiv:1610.05771Towards an automated tool to evaluate the impact of the nuclear modification of the gluon density on quarkonium, D and B meson production in proton-nucleus collisions
http://cds.cern.ch/record/2226219
We propose a simple and model-independent procedure to account for the impact of the nuclear modification of the gluon density as encoded in nuclear collinear PDF sets on two-to-two partonic hard processes in proton-nucleus collisions. This applies to a good approximation to quarkonium, D and B meson production, generically referred to H. Our procedure consists in parametrising the square of the parton scattering amplitude, A_{gg -> H X} and constraining it from the proton-proton data. Doing so, we have been able to compute the corresponding nuclear modification factors for J/psi, Upsilon and D^0 as a function of y and P_T at sqrt(s_NN)=5 and 8 TeV in the kinematics of the various LHC experiments in a model independent way. It is of course justified since the most important ingredient in such evaluations is the probability of each kinematical configuration. Our computations for D mesons can also be extended to B meson production. To further illustrate the potentiality of the tool, we provide --for the first time-- predictions for the nuclear modification factor for eta_c production in pPb collisions at the LHC.Lansberg, Jean-PhilippeShao, Hua-ShengThu, 20 Oct 2016 06:40:24 GMT17 Oct 2016arXiv:1610.05382http://cds.cern.ch/record/2226219['arXiv:1610.05382']arXiv:1610.05382QCD next-to-leading order predictions matched to parton showers for vector-like quark models
http://cds.cern.ch/record/2225709
Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair-production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup. We additionally compute vector-like-quark contributions to the production of a pair of Standard Model bosons at the same level of accuracy. For all processes under consideration, we focus both on total cross sections and on differential distributions, most these calculations being performed for the first time in our field. As a result, our work paves the way to precise extraction of experimental limits on vector-like quarks thanks to an accurate control of the shapes of the relevant observables and emphasize the extra handles that could be provided by novel vector-like-quark probes never envisaged so farFuks, BenjaminShao, Hua-ShengTue, 18 Oct 2016 06:01:20 GMT14 Oct 2016arXiv:1610.04622http://cds.cern.ch/record/2225709['arXiv:1610.04622']arXiv:1610.04622