Showing papers on "Elementary particle published in 2009"

Vector boson production at hadron colliders: a fully exclusive QCD calculation at next-to-next-to-leading order.

Abstract: We consider QCD radiative corrections to the production of W and Z bosons in hadron collisions. We present a fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform this NNLO computation, we use a recently proposed version of the subtraction formalism. The calculation includes the gamma-Z interference, finite-width effects, the leptonic decay of the vector bosons, and the corresponding spin correlations. Our calculation is implemented in a parton level Monte Carlo program. The program allows the user to apply arbitrary kinematical cuts on the final-state leptons and the associated jet activity and to compute the corresponding distributions in the form of bin histograms. We show selected numerical results at the Fermilab Tevatron and the LHC.

Observation of single top-quark production

Abstract: We report observation of the electroweak production of single top quarks in pp collisions at s=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(pp -> tb+X,tqb+X)=3.94 +/- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5x10(-7), corresponding to a 5.0 standard deviation significance for the observation.

Models of Yukawa interaction in the two Higgs doublet model, and their collider phenomenology

Abstract: Possible models of Yukawa interaction are discussed in the two Higgs doublet model (THDM) under the discrete symmetry imposed to avoid the flavor changing neutral current at the leading order. It is known that there are four types of such models corresponding to the possible different assignment of charges for the discrete symmetry on quarks and leptons. We first examine the decay properties of Higgs bosons in each type model, and summarize constraints on the models from current experimental data. We then shed light on the differences among these models in collider phenomenology. In particular, we mainly discuss the so-called type-II THDM and type-X THDM. The type-II THDM corresponds to the model with the same Yukawa interaction as the minimal supersymmetric standard model. On the other hand, in the type-X THDM, additional Higgs bosons can predominantly decay into leptons. This scenario may be interesting because of the motivation for a light charged Higgs boson scenario such as in the TeV-scale model of neutrinos, dark matter, and baryogenesis. We study how we can distinguish the type-X THDM from the minimal supersymmetric standard model at the Large Hadron Collider and the International Linear Collider.

Renormalization-group improved prediction for Higgs production at hadron colliders

Abstract: We use renormalization-group methods in effective field theory to improve the theoretical prediction for the cross section for Higgs-boson production at hadron colliders. In addition to soft-gluon resummation at N3LL, we also resum enhanced contributions of the form (C A π α s ) n , which arise in the analytic continuation of the gluon form factor to time-like momentum transfer. This resummation is achieved by evaluating the matching corrections arising at the Higgs-boson mass scale at a time-like renormalization point μ 2<0, followed by renormalization-group evolution to μ 2>0. We match our resummed result to NNLO fixed-order perturbation theory and give numerical predictions for the total production cross section as a function of the Higgs-boson mass. Resummation effects are significant even at NNLO, where our improved predictions for the cross sections at the Tevatron and the LHC exceed the fixed-order predictions by about 13% and 8%, respectively, for m H =120 GeV. We also discuss the application of our technique to other time-like processes such as Drell–Yan production, e + e −→hadrons, and hadronic decays of the Higgs boson.

The Isotropic Diffusion Source Approximation for Supernova Neutrino Transport

Abstract: Astrophysical observations originate from matter that interacts with radiation or transported particles. We develop a pragmatic approximation in order to enable multidimensional simulations with basic spectral radiative transfer when the available computational resources are not sufficient to solve the complete Boltzmann transport equation. The distribution function of the transported particles is decomposed into a trapped particle component and a streaming particle component. Their separate evolution equations are coupled by a source term that converts trapped particles into streaming particles. We determine this source term by requiring the correct diffusion limit for the evolution of the trapped particle component. For a smooth transition to the free streaming regime, this "diffusion source" is limited by the matter emissivity. The resulting streaming particle emission rates are integrated over space to obtain the streaming particle flux. Finally, a geometric estimate of the flux factor is used to convert the particle flux to the streaming particle density, which enters the evaluation of streaming particle-matter interactions. The efficiency of the scheme results from the freedom to use different approximations for each particle component. In supernovae, for example, reactions with trapped particles on fast timescales establish equilibria that reduce the number of primitive variables required to evolve the trapped particle component. On the other hand, a stationary-state approximation considerably facilitates the treatment of the streaming particle component. Different approximations may apply in applications to stellar atmospheres, star formation, or cosmological radiative transfer. We compare the isotropic diffusion source approximation with Boltzmann neutrino transport of electron flavor neutrinos in spherically symmetric supernova models and find good agreement. An extension of the scheme to the multidimensional case is also discussed.

Precision Determination of Electroweak Coupling from Atomic Parity Violation and Implications for Particle Physics

Abstract: We carry out high-precision calculation of parity violation in a cesium atom, reducing theoretical uncertainty by a factor of 2 compared to previous evaluations. We combine previous measurements with calculations and extract the weak charge of the 133Cs nucleus, QW=-73.16(29)expt(20)theor. The result is in agreement with the standard model (SM) of elementary particles. This is the most accurate to-date test of the low-energy electroweak sector of the SM. In combination with the results of high-energy collider experiments, we confirm the energy dependence (or "running") of the electroweak force over an energy range spanning 4 orders of magnitude (from approximately 10 MeV to approximately 100 GeV). Additionally, our result places constraints on a variety of new physics scenarios beyond the SM. In particular, we increase the lower limit on the masses of extra Z bosons predicted by models of grand unification and string theories.

Higgs mediated flavor changing neutral currents in warped extra dimensions

Abstract: In the context of a warped extra dimension with standard model fields in the bulk, we obtain the general flavor structure of the Higgs couplings to fermions. These couplings will be generically misaligned with respect to the fermion mass matrix, producing large and potentially dangerous flavor changing neutral currents. As recently pointed out [K. Agashe and R. Contino, arXiv:0906.1542.], a similar effect is expected from the point of view of a composite Higgs sector, which corresponds to a four-dimensional theory dual to the five-dimensional setup by the AdS/CFT correspondence. We also point out that the effect is independent of the geographical nature of the Higgs (bulk or brane localized), and specifically that it does not go away as the Higgs is pushed towards the IR boundary. The flavor changing neutral currents mediated by a light enough Higgs (especially their contribution to {epsilon}{sub K}) could become of comparable size as the ones coming from the exchange of Kaluza-Klein gluons. Moreover, both sources of flavor violation are complementary since they have inverse dependence on the five-dimensional Yukawa couplings, such that we cannot decouple the flavor violation effects by increasing or decreasing these couplings. We also find that for Kaluza-Klein scales of amore » few TeV, the Higgs couplings to third generation fermions could experience suppressions of up to 40% while the rest of diagonal couplings would suffer much milder corrections. Potential LHC signatures like the Higgs flavor violating decays h{yields}{mu}{tau} or h{yields}tc, or the exotic top decay channel t{yields}ch, are finally addressed.« less

Revisiting the Global Electroweak Fit of the Standard Model and Beyond with Gfitter

Abstract: The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working group and others, demonstrated impressively the predictive power of electroweak unification and quantum loop corrections. We have revisited this fit in view of (i) the development of the new generic fitting package, Gfitter, allowing for flexible and efficient model testing in high-energy physics, (ii) the insertion of constraints from direct Higgs searches at LEP and the Tevatron, and (iii) a more thorough statistical interpretation of the results. Gfitter is a modular fitting toolkit, which features predictive theoretical models as independent plug-ins, and a statistical analysis of the fit results using toy Monte Carlo techniques. The state-of-the-art electroweak Standard Model is fully implemented, as well as generic extensions to it. Theoretical uncertainties are explicitly included in the fit through scale parameters varying within given error ranges. This paper introduces the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model (SM), and for a model with an extended Higgs sector (2HDM). Numerical and graphical results for fits with and without including the constraints from the direct Higgs searches at LEP and Tevatron are given. Perspectives for future colliders are analysed and discussed. In the SM fit including the direct Higgs searches, we find M H =116.4 −1.3 +18.3 GeV, and the 2σ and 3σ allowed regions [114,145] GeV and [[113,168] and [180,225]] GeV, respectively. For the strong coupling strength at fourth perturbative order we obtain α S (M 2 )=0.1193 −0.0027 +0.0028 (exp )±0.0001 (theo). Finally, for the mass of the top quark, excluding the direct measurements, we find m t =178.2 −4.2 +9.8 GeV. In the 2HDM we exclude a charged-Higgs mass below 240 GeV at 95% confidence level. This limit increases towards larger tan β, e.g., $M_{H^{\pm}}<780\ \mbox{GeV}$ is excluded for tan β=70.

Probing the gluon self-interaction in light mesons

Abstract: We investigate masses and decay constants of light mesons from a coupled system of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly take into account dominant non-Abelian contributions to the dressed quark-gluon vertex stemming from the gluon self-interaction. We construct the corresponding Bethe-Salpeter kernel that satisfies the axial-vector Ward-Takahashi identity. Our numerical treatment fully includes all momentum dependencies with all equations solved completely in the complex plane. This approach goes well beyond the rainbow-ladder approximation and permits us to investigate the influence of the gluon self-interaction on the properties of mesons. As a first result we find indications of a nonperturbative cancellation of the gluon self-interaction contributions and pion cloud effects in the mass of the rho meson.

IDM and iDM or The Inert Doublet Model and Inelastic Dark Matter

Abstract: The annual modulation observed by DAMA/NaI and DAMA/Libra may be interpreted in terms of elastic or inelastic scattering of dark matter particles. In this paper we confront these two scenarios within the framework of a very simple extension of the Standard Model, the Inert Doublet Model (IDM). In this model the dark matter candidate is a scalar, the lightest component of an extra Higgs doublet. We first revisit the case for the elastic scattering of a light scalar WIMP, MDM ~ 10 GeV, a scenario which requires that a fraction of events in DAMA are channelled. Second we consider the possibility of inelastic Dark Matter (iDM). This option is technically natural in the IDM, in the sense that the mass splitting between the lightest and next-to-lightest neutral scalars may be protected by a Peccei-Quinn (PQ) symmetry. We show that candidates with a mass MDM between ~ 535 GeV and ~ 50 TeV may reproduce the DAMA data and have a cosmic abundance in agreement with WMAP. This range may be extended to candidates as light as ~ 50 GeV if we exploit the possibility that the approximate PQ symmetry is effectively conserved and that a primordial asymmetry in the dark sector may survive until freeze-out.

Search for Charged Higgs Bosons in Decays of Top Quarks in pp̅ Collisions at √s=1.96 TeV

Abstract: We report on the first direct search for charged Higgs bosons in decays of top quarks in p{bar p} collisions at {radical}s = 1.96 TeV. The search uses a data sample corresponding to an integrated luminosity of 2.2 fb{sup -1} collected by the CDF II detector at Fermilab, and looks for a resonance in the invariant mass distribution of two jets in the lepton+jets sample of t{bar t} candidates. We observe no evidence of charged Higgs bosons in top quark decays. Hence, 95% upper limits on the top quark decay branching ratio are placed at {Beta}(t {yields} H{sup +}b) < 0.1 to 0.3 for charged Higgs boson masses of 60 to 150 GeV/c{sup 2}, assuming {Beta}(H{sup +} {yields} c{bar s}) = 1.0. The upper limits on {Beta}(t {yields} H{sup +}b) can also be used as model-independent limits on the decay branching ratio of top quarks to generic scalar charged bosons beyond the standard model.

P-Adic Length Scale Hypothesis and Dark Matter Hierarchy

Abstract: The book is devoted to the applications of p-adic length scale hypothesis and dark matter hierarchy. p-Adic length scale hypothesis states that primes p≈ 2k, k integer, in particular prime, define preferred p-adic length scales. Physical arguments supporting this hypothesis are based on the generalization of Hawking's area law for blackhole entropy so that it applies in case of elementary particles. A deeper number theory based justification for this hypothesis is based on the generalization of the number concept fusing real number fields and p-adic number fields among common rationals or numbers in their non-trivial algebraic extensions. This approach also justifies the notion of multi-p-fractality and allows to understand scaling law in terms of simultaneous p≈ 2k- and 2-fractality. In TGD framework the levels of dark matter hierarchy are labeled by the values of dynamical quantized Planck constant. The justification for the hypothesis provided by quantum classical correspondence and the fact the sizes of space-time sheets identifiable as quantum coherence regions can be arbitrarily large. The weak form of electric-magnetic duality is the newest building brick of the vision and leads to a detailed view about electro-weak screening and color confinement and predicts new physics below weak scales. The weak form of electric-magnetic duality allows to identify Higgs bosons and to understand how they provide the longitudinal polarizations of gauge bosons. The most natural option is that photon eats the remaining Higgs scalar and receives a small mass. This true for all bosons regarded as massless and allows to have exact Yangian symmetry requiring the vanishing of IR divergences. Higgs potential and vacuum expectation of Higgs are not needed in the model. Twistors emerge naturally in TGD framework and several proposal for twistorialization of TGD is discussed in two chapters devoted to the topic. Twistorial approach combined with zero energy ontology, bosonic emergence, and the properties of the Chern-Simons Dirac operator leads to the conjecture that all particles -also string like objects- can be regarded as bound states of massless particles identifiable as wormhole throats. Also virtual particles would consist of massles wormhole throats but bound state property is not assumed anymore and the energies of wormhole throats can have opposite signs so that space-like momentum exchanges become possible. This implies extremely strong constraints on loop momenta and manifest finiteness of loop integrals. The first part of the book is about the description of elementary particle massivation in terms of p-adic thermodynamics and Higgsy contribution affecting the vacuum conformal weight. In the first chapter the view about quantum TGD from particle physics perspective is discussed and the remaining chapters are devoted to the detailed calculation of masses of elementary particles and hadrons, and to various new physics suggested or predicted by the resulting scenario. Second part of the book is devoted to the application of p-adic length scale hypothesis above elementary particle length scales. The so called leptohadron physics, originally developed on basis of experimental anomalies, is discussed as a particular instance of an infinite fractal hierarchy of copies of standard model physics, predicted by TGD and consistent with what is known about ordinary elementary particle physics. TGD based view about nuclear physics involves light exotic quarks as a essential element, and dark nuclear physics could have implications also at the level of condensed matter physics and biology. TGD based view about high Tc superconductors involves also in an essential manner dark matter and is summarized in the closing chapter.

Split universal extra dimension and dark matter

Abstract: Motivated by the recent observation of the high energy electron and positron excesses in cosmic ray by PAMELA and ATIC/PPB-BETS, we suggest an anomaly-free scenario for the universal extra dimension that localizes the standard model quarks and splits the spectrum of Kaluza-Klein (KK) quarks from KK leptons. When the SM quarks are 'well localized' at the boundaries, the most stringent bound of the model (1/R>510 GeV) comes from the resonance search for the Tevatron dijet channels. Even at the early stage of LHC, one can discover the second KK gluon for masses up to 4 TeV.

B̄→D*ℓν̄ form factor at zero recoil from three-flavor lattice QCD: A model independent determination of |Vcb|

Abstract: We present the first lattice QCD calculation of the form factor for $\overline{B}\ensuremath{\rightarrow}{D}^{*}\ensuremath{\ell}\overline{\ensuremath{ u}}$ with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC configurations), and the Fermilab action for the heavy quarks. The form factor is computed at zero recoil using a new double ratio method that yields the form factor more directly than the previous Fermilab method. Other improvements over the previous calculation include the use of much lighter light-quark masses, and the use of lattice (staggered) chiral perturbation theory in order to control the light-quark discretization errors and chiral extrapolation. We obtain for the form factor, ${\mathcal{F}}_{B\ensuremath{\rightarrow}{D}^{*}}(1)=0.921(13)(20)$, where the first error is statistical and the second is the sum of all systematic errors in quadrature. Applying a 0.7% electromagnetic correction and taking the latest PDG average for ${\mathcal{F}}_{B\ensuremath{\rightarrow}{D}^{*}}(1)|{V}_{cb}|$ leads to $|{V}_{cb}|=(38.7\ifmmode\pm\else\textpm\fi{}{0.9}_{\mathrm{exp} }\ifmmode\pm\else\textpm\fi{}{1.0}_{\mathrm{theo}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$.

Lennard-Jones quark matter and massive quark stars

Abstract: Quark clustering could occur in cold quark matter because of the strong coupling between quarks at realistic baryon densities of compact stars Although one may still not be able to calculate this conjectured matter from first principles, the inter-cluster interaction might be analogized to the interaction between inert molecules Cold quark matter would then crystallize in a solid state if the inter-cluster potential is deep enough to trap the clusters in the wells We apply the Lennard-Jones potential to describe the inter-cluster potential, and derive the equations of state, which are stiffer than that derived in conventional models (eg, MIT bag model) If quark stars are composed of Lennard-Jones matter, they could have high maximum masses ($>2M_{\odot}$) as well as very low masses ($<10^{-3}M_{\odot}$) These features could be tested by observations

Electroweak phase transition, critical bubbles and sphaleron decoupling condition in the MSSM

Abstract: The electroweak phase transition and the sphaleron decoupling condition in the minimal supersymmetric standard model are revisited taking the latest experimental data into account. The light Higgs boson scenario and the ordinary decoupling limit, which are classified by the relative size between the $CP$-odd Higgs boson mass and $Z$ boson mass, are considered within the context of electroweak baryogenesis. We investigate $v/T$ at not only the critical temperature at which the effective potential has two degenerate minima but also the nucleation temperature of the critical bubbles, where $v$ is a vacuum expectation value of the Higgs boson and $T$ denotes a temperature. It is found that $v/T$ at the nucleation temperature can be enhanced by about 10% compared to that at the critical temperature. We also evaluate the sphaleron decoupling condition including the zero mode factors of the fluctuations around sphaleron. It is observed that the sphaleron decoupling condition at the nucleation temperature is given by $v/T\ensuremath{\gtrsim}1.38$ for the typical parameter sets. In any phenomenologically allowed region, $v/T$ at both the critical and nucleation temperatures cannot be large enough to satisfy such a sphaleron decoupling condition.

Measuring the Higgs boson mass in dileptonic W -boson decays at hadron colliders

Abstract: It is expected that hadron collider measurements of the Higgs boson mass using the decay h→W+W−, followed by the leptonic decay of each W-boson, will be performed by fitting the shape of a distribution that is sensitive to the Higgs mass. We demonstrate that the variable most commonly used to measure the Higgs mass in this channel is not optimal as it contains an unnecessary and even counter-productive approximation. We remove that approximation, without introducing any cost in complexity, and demonstrate that the new variable is a clear improvement over the old: its performance is never worse, and in some cases (particularly the high Higgs mass region) it might reduce the fit uncertainty on the Higgs mass in that channel by a factor approaching two.

Can we discover dual-component thermal WIMP dark matter?

Abstract: We address the question of whether the upcoming generation of dark matter search experiments and colliders will be able to discover if the dark matter in the Universe has two components of weakly interacting massive particles (WIMPs). We outline a model-independent approach, and we study the specific cases of (1) direct detection with low-background 1 ton noble-gas detectors and (2) a 0.5 TeV center of mass energy electron-positron linear collider. We also analyze the case of indirect detection via two gamma-ray lines, which would provide a verification of such a discovery, although multiple gamma-ray lines can in principle originate from the annihilation of a single dark matter particle. For each search ``channel'', we outline a few assumptions to relate the very small set of parameters we consider (defining the masses of the two WIMPs and their relative abundance in the overall dark matter density) with the relevant detection rates. We then draw general conclusions on which corners of a generic dual-component dark matter scenario can be explored with current and next generation experiments. We find that in all channels the ideal setup is one where the relative mass splitting between the two WIMP species is of order 1, and where the two dark matter components contribute in a ratio close to 1:1 to the overall dark matter content of the Universe. Interestingly, in the case of direct detection, future experiments might detect multiple states even if only ~ 10% of the energy-density of dark matter in the Universe is in the subdominant species.

A model independent spin analysis of fundamental particles using azimuthal asymmetries

Abstract: Exploiting the azimuthal angle dependence of the density matrices we construct observables that directly measure the spin of a heavy unstable particle. A novelty of the approach is that the analysis of the azimuthal angle dependence in a frame other than the usual helicity frame offers an independent cross-check on the extraction of the spin. Moreover, in some instances when the transverse polarisation tensor of highest rank is vanishing, for an accidental or dynamical reason, the standard azimuthal asymmetries vanish and would lead to a measurement with a wrong spin assignment. In a frame such as the one we construct, the correct spin assignment would however still be possible. The method gives direct information about the spin of the particle under consideration and the same event sample can be used to identify the spins of each particle in a decay chain. A drawback of the method is that it is instrumental only when the momenta of the test particle can be reconstructed. However we hope that it might still be of use in situations with only partial reconstruction. We also derive the conditions on the production and decay mechanisms for the spins, and hence the polarisations, to be measured at a collider experiment. As an example for the use of the method we consider the simultaneous reconstruction, at the partonic level, of the spin of both the top and the W in top pair production in e + e − in the semi-leptonic channel.

Novel Reconstruction Technique for New Physics Processes with Initial State Radiation

Abstract: The production of heavy particles at hadron colliders is associated with radiation of additional quarks and gluons from incoming partons They can have significant transverse momenta and the additional initial state radiation (ISR) jets complicate the reconstruction of new particle masses Taking gluino pair production and decay at the Large Hadron Collider as an example, we develop a novel technique to reduce these effects, allowing for a better reconstruction of masses through the measurement of kinematical end points

Search for Higgs Bosons Predicted in Two-Higgs-Doublet Models via Decays to Tau Lepton Pairs in 1.96 TeV pp Collisions

Abstract: We present the results of a search for Higgs bosons predicted in two-Higgs-doublet models, in the case where the Higgs bosons decay to tau lepton pairs, using 1.8 fb{sup -1} of integrated luminosity of p{bar p} collisions recorded by the CDF II experiment at the Fermilab Tevatron. Studying the mass distribution in events where one or both tau leptons decay leptonically, no evidence for a Higgs boson signal is observed. The result is used to infer exclusion limits in the two-dimensional space of tan {beta} versus m{sub A} (the ratio of the vaccum expectation values of the two Higgs doublets and the mass of the pseudoscalar boson, respectively).

Energy-momentum diffusion from spacetime discreteness

Abstract: We study potentially observable consequences of spatiotemporal discreteness for the motion of massive and massless particles. First we describe some simple models for the motion of a massive point particle in a fixed causal set background. If the causal set is faithfully embeddable in Minkoswki spacetime, the models give rise to particle motion in the continuum spacetime. At large scales, the microscopic swerves induced by the underlying atomicity manifest themselves as a Lorentz invariant diffusion in energy-momentum governed by a single phenomenological parameter, and we derive in full the corresponding diffusion equation. Inspired by the simplicity of the result, we then derive the most general Lorentz invariant diffusion equation for a massless particle, which turns out to contain two phenomenological parameters describing, respectively, diffusion and drift in the particle's energy. The particles do not leave the light cone however: their worldlines continue to be null geodesics. Finally, we deduce bounds on the drift and diffusion constants for photons from the blackbody nature of the spectrum of the cosmic microwave background radiation.

LHC discovery potential of a leptophilic Higgs boson

Abstract: In this work, we examine a two-Higgs-doublet extension of the standard model in which one Higgs doublet is responsible for giving mass to both up- and down-type quarks, while a separate doublet is responsible for giving mass to leptons. We examine both the theoretical and experimental constraints on the model and show that large regions of parameter space are allowed by these constraints in which the effective couplings between the lightest neutral Higgs scalar and the standard-model leptons are substantially enhanced. We investigate the collider phenomenology of such a 'leptophilic' two-Higgs-doublet model and show that in cases where the low-energy spectrum contains only one light, CP-even scalar, a variety of collider processes essentially irrelevant for the discovery of a standard model Higgs boson (specifically those in which the Higgs boson decays directly into a charged-lepton pair) can contribute significantly to the discovery potential of a light-to-intermediate-mass (m{sub h} < or approx. 140 GeV) Higgs boson at the LHC.

Search for resonant pair production of neutral long-lived particles decaying to bb̄ in pp̄ collisions at s=1.96TeV

Abstract: We report on a first search for resonant pair production of neutral long-lived particles (NLLP) which each decay to a b (b) over bar pair, using 3.6 fb(-1) of data recorded with the D0 detector at the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6-20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.

Pragmatic Approach to the Little Hierarchy Problem: The Case for Dark Matter and Neutrino Physics

Abstract: We show that the addition of real scalars (gauge singlets) to the standard model can both ameliorate the little hierarchy problem and provide realistic dark matter candidates. To this end, the coupling of the new scalars to the standard Higgs boson must be relatively strong and their mass should be in the 1-3 TeV range, while the lowest cutoff of the (unspecified) UV completion must be > or approx. 5 TeV, depending on the Higgs boson mass and the number of singlets present. The existence of the singlets also leads to realistic, and surprisingly reach, neutrino physics. The resulting light neutrino mass spectrum and mixing angles are consistent with the constraints from the neutrino oscillations.

Search for next-to-minimal supersymmetric higgs bosons in the h→aa→μμμμ, μμττ channels using pp̄ collisions at s=1.96TeV

Abstract: We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs bosons (a), using 4.2 fb{sup -1} of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to {mu}{sup +}{mu}{sup -} or one to {mu}{sup +}{mu}{sup -} and the other to {tau}{sup +}{tau}{sup -}. No significant signal is observed, and we set limits on its production as functions of M{sub a} and M{sub h}.