arXiv subjects

Kai Wang

Publications and source records attributed to Kai Wang.

At least 883 records · Page 49Linked to original sources

arXiv2010

NLSP Gluino Search at the Tevatron and early LHC

We investigate the collider phenomenology of gluino-bino co-annihilation scenario both at the Tevatron and 7 TeV LHC. This scenario can be realized, for example, in a class of realistic supersymmetric models with non-universal gaugino masses and t-b-τYukawa unification. The NLSP gluino and LSP bino should be nearly degenerate in mass, so that the typical gluino search channels involving leptons or hard jets are not available. Consequently, the gluino can be lighter than various bounds on its mass from direct searches. We propose a new search for NLSP gluino involving multi-b final states, arising from the three-body decay \tilde{g}-> b\bar{b}\tildeχ_1^0. We identify two realistic models with gluino mass of around 300 GeV for which the three-body decay is dominant, and show that a 4.5 σobservation sensitivity can be achieved at the Tevatron with an integrated luminosity of 10 fb^{-1}. For the 7 TeV LHC with 50 pb^{-1} of integrated luminosity, the number of signal events for the two models is O(10), to be compared with negligible SM background event.

hep-ph↗

arXiv2010

TeV scale horizontal gauge symmetry and its implications in B-physics

We propose a gauged $U(1)_{H}$ horizontal symmetry around TeV scale that is a subgroup of a $SU(3)_{H}$ horizontal gauge symmetry broken at ${\cal O}(10^{14}) \GeV$. The breaking generates right-handed Majorana neutrino masses through a $SU(3)_H$ sextet scalar. A particular Majorana right-handed neutrino mass matrix explicitly determines the remnant $U(1)_{H}$ at low energy which only couples to $b-s$ and $μ-τ$ in the gauge eigenstate. The dangerous $K-\bar{K}$, $D-\bar{D}$ mixing and $B_s \rightarrow μ^+ μ^-$ are kept to be safe because the relevant couplings are suppressed through high powers of small mixing angles in the fermion rotation matrix. Our analysis which applies to the general case shows that the Tevatron di-muon anomaly can be explained through the $B_{s}$ and $B_{d}$ mixing while keeping all the other experimental constraints within 90 \% C. L. For the $B$ meson decay, the $B_{s}\to μ^{\pm}τ^{\mp}$ is the leading leptonic decay channel which is several orders of magnitude below current experimental bound.

hep-ph↗

arXiv2010

Nearly Degenerate Gauginos and Dark Matter at the LHC

Motivated by dark-matter considerations in supersymmetric theories, we investigate in a fairly model-independent way the detection at the LHC of nearly degenerate gauginos with mass differences between a few GeV and about 30 GeV. Due to the degeneracy of gaugino states, the conventional leptonic signals are likely lost. We first consider the leading signal from gluino production and decay. We find that it is quite conceivable to reach a large statistical significance for the multi-jet plus missing energy signal with an integrated luminosity about 50 pb^-1 (50 fb^-1) for a gluino mass of 500 GeV (1 TeV). If gluinos are not too heavy, less than about 1.5 TeV, this channel can typically probe gaugino masses up to about 100 GeV below the gluino mass. We then study the Drell-Yan type of gaugino pair production in association with a hard QCD jet, for gaugino masses in the range of 100-150 GeV. The signal observation may be statistically feasible with about 10 fb^-1, but systematically challenging due to the lack of distinctive features for the signal distributions. By exploiting gaugino pair production through weak boson fusion, signals of large missing energy plus two forward-backward jets may be observable at a 4-6σlevel above the large SM backgrounds with an integrated luminosity of 100-300 fb^-1. Finally, we point out that searching for additional isolated soft muons in the range p_T ~3-10 GeV in the data samples discussed above may help to enrich the signal and to control the systematics. Significant efforts are made to explore the connection between the signal kinematics and the relevant masses for the gluino and gauginos, to probe the mass scales of the superpartners, in particular the LSP dark matter.

hep-ph↗

arXiv2010

Invisible Higgs decay with B\to Kν\barν constraint

If the Higgs boson were the only particle within the LHC accessible range, precision measurement of the Higgs's properties would play a unique role in studying electroweak symmetry breaking as well as possible new physics. We try to use low energy experiments such as rare B decay to constrain a challenging decay mode of Higgs, in which a Higgs decays to a pair of light (\approx 1 \sim 2 GeV) SM singlet S and becomes invisible. By using the current experimental bound of rare decay B\to Kν\barν and computing the contribution of B\to K SS to (the) B\to K+\cancel{E}, we obtain an upper bound on the Higgs coupling to such light singlet. It is interesting that the partial width of the invisible decay mode h\to SS by taking the upper bound value of coupling is at a comparable level with h\to WW/ZZ or WW^(*) decay modes, making the Higgs identifiable but with a different predicted decay BR from the standard model Higgs decay. It will then have an impact on precision measurement of the Higgs's properties. We also study the implication for cosmology from such a light singlet and propose a solution to the potential problem.

hep-ph↗

arXiv2010

Axigluon as Possible Explanation for $p\bar{p} \to t\bar{t}$ Forward-Backward Asymmetry

A flavor-nonuniversal chiral color model is introduced. It is used for comparison to the recent data on $\bar{p} p \to \bar{t} t$. We concluded that the data are consistent with interpretation as an axigluon exchange within 1$σ$ and a unique rise and fall behavior is predicated with regard to the asymmetry $A^t_{FB}$ as a function of $t \bar{t}$ invariant mass, which can distinguish our model from others before one discovers the axigluon resonance. Further aspects of the model are discussed.

hep-ph↗

arXiv2010

Multivariate dependence and genetic networks inference

A critical task in systems biology is the identification of genes that interact to control cellular processes by transcriptional activation of a set of target genes. Many methods have been developed to use statistical correlations in high-throughput datasets to infer such interactions. However, cellular pathways are highly cooperative, often requiring the joint effect of many molecules, and few methods have been proposed to explicitly identify such higher-order interactions, partially due to the fact that the notion of multivariate statistical dependency itself remains imprecisely defined. We define the concept of dependence among multiple variables using maximum entropy techniques and introduce computational tests for their identification. Synthetic network results reveal that this procedure uncovers dependencies even in undersampled regimes, when the joint probability distribution cannot be reliably estimated. Analysis of microarray data from human B cells reveals that third-order statistics, but not second-order ones, uncover relationships between genes that interact in a pathway to cooperatively regulate a common set of targets.

q-bio.QM↗

arXiv2009

Explorations of the Top Quark Forward-Backward Asymmetry at the Tevatron

We consider the recent measurement of the top quark forward-backward asymmetry at the Fermilab Tevatron, which shows a discrepancy of slightly more than 2$σ$ compared to the SM prediction. We find that $t$-channel exchange of a color sextet or triplet scalar particle can explain the measurement, while leaving the cross section for $t \bar{t}$ production within measured uncertainties. Such particles have good discovery prospects by study of the kinematic structure of $t \bar{t}$+jets at the LHC.

hep-ph↗

arXiv2009

QCD radiative correction to color-octet $J/ψ$ inclusive production at B Factories

In nonrelativistic Quantum Chromodynamics (NRQCD), we study the next-to-leading order (NLO) QCD radiative correction to the color-octet $J/ψ$ inclusive production at B Factories. Compared with the leading-order (LO) result, the NLO QCD corrections are found to enhance the short-distance coefficients in the color-octet $J/ψ$ production $ e^+ e^-\to c \bar c (^3P_0^{(8)} {\rm or} ^3P_0^{(8)})g$ by a factor of about 1.9. Moreover, the peak at the endpoint in the $J/ψ$ energy distribution predicted at LO can be smeared by the NLO corrections, but the major color-octet contribution still comes from the large energy region of $J/ψ$. By fitting the latest data of $σ(e^{+}e^{-}\to J/ψ+X_{\mathrm{non-c\bar{c}}})$ observed by Belle, we find that the values of color-octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with LO calculations. As the most stringent constraint by setting the color-singlet contribution to be zero in $e^{+}e^{-}\to J/ψ+X_{\mathrm{non-c\bar{c}}}$, we get an upper limit of the color-octet matrix element, $<0| {\cal O}^{J/ψ}[{}^1S_0^{(8)}]|0> + 4.0 <0| {\cal O}^{J/ψ} [{}^3P_0^{(8)}]|0>/m_c^2 <(2.0 \pm 0.6)\times 10^{-2} {\rm GeV}^3$ at NLO in $α_s$.

hep-ph↗

arXiv2009

Neutrino mass from a hidden world and its phenomenological implications

We propose a model of neutrino mass generation in extra dimension. Allowing a large lepton number violation on a distant brane spatially separated from the standard model brane, a small neutrino mass is naturally generated due to an exponential suppression of the messenger field in the 5D bulk. The model accommodates a large Yukawa coupling with the singlet neutrino (n_R) which may change the standard Higgs search and can simultaneously accommodate visible lepton number violation at the electroweak scale, which leads to very interesting phenomenology at the CERN Large Hadron Collider.

hep-ph↗

arXiv2009

Like-sign Di-lepton Signals in Higgsless Models at the LHC

We study the potential LHC discovery of the Z1 KK gauge boson unitarizing longitudinal W+W- scattering amplitude. In particular, we explore the decay mode Z1->t tbar along with Z1-> W+W- without specifying the branching fractions. We propose to exploit the associated production pp-> W Z1, and select the final state of like-sign dileptons plus multijets and large missing energy. We conclude that it is possible to observe the Z1 resonance at a 5 sigma level with an integrated luminosity of 100 inverse fb at the LHC upto 650 GeV for a dominant WW channel, and 560 GeV for a dominant ttbar channel.

hep-ph↗

arXiv2009

Color Sextet Scalars at the CERN Large Hadron Collider

Taking a phenomenological approach, we study a color sextet scalar at the LHC. We focus on the QCD production of a color sextet pair Φ_6\barΦ_{6} through gg fusion and q\bar{q} annihilation. Its unique coupling to \bar{ψ^c}ψallows the color sextet scalar to decay into same-sign diquark states, such as Φ_6\to tt/tt^*. We propose a new reconstruction in the multijet plus same sign dilepton with missing transverse energy samples to search for on-shell tt\bar{t}\bar{t} final states from sextet scalar pair production. Thanks to the large QCD production, the search covers the sextet mass range up to 1 TeV for 100 fb^-1 integrated luminosity.

hep-ph↗

arXiv2009

Triplet Scalars and Dark Matter at the LHC

We investigate the predictions of a simple extension of the Standard Model where the Higgs sector is composed of one $SU(2)_L$ doublet and one real triplet. We discuss the general features of the model, including its vacuum structure, theoretical and phenomenological constraints, and expectations for Higgs collider studies. The model predicts the existence of a pair of light charged scalars and, for vanishing triplet vacuum expectation value, contains a cold dark matter candidate. When the latter possibility occurs, the charged scalars are long-lived, leading to a prediction of distinctive single charged track with missing transverse energy or double charged track events at the LHC. The model predicts a significant excess of two-photon events compared to SM expectations due to the presence of a light charged scalar.

hep-ph↗

arXiv2008

GeV Majorana Neutrinos in Top-quark Decay at the LHC

We explore the ΔL=2 same-sign dilepton signal from top-quark decay via a Majorana neutrino at the LHC in the top anti-top pair production samples. The signature is same-sign dilepton plus multi-jets with no significant missing energy. The most optimistic region lies where the Majorana neutrino mass is between 15-65 GeV. For 300 fb^-1 integrated luminosity, it is possible to probe S_{ij}, the effective mixing parameter, to order of 10^-5.

hep-ph↗

arXiv2008

Testing a Neutrino Mass Generation Mechanism at the Large Hadron Collider

The Large Hadron Collider could be a discovery machine for the neutrino mass pattern and its Majorana nature in the context of a well-motivated TeV scale Type II seesaw model. This is achieved by identifying the flavor structure of the lepton number violating decays of the charged Higgs bosons. The observation of either H^+ --> tau^+ nubar or H^+ --> e^+ nubar will be particularly robust to determine the neutrino spectra since they are independent of the unknown Majorana phases, which could be probed via the H^{++} --> e^+_i e^+_j decays. In a less favorable scenario when the leptonic channels are suppressed, one needs to observe the decays H^+ --> W^+ H_1, and H^+ --> t bbar to confirm the triplet-doublet mixing that implies the Type II relation. The associated production H^{++} H^{-} is crucial in order to test the triplet nature of the Higgs field.

hep-ph↗

arXiv2008

Applied Symbolic Vector Dynamics of Coupled Map Lattice

Symbolic dynamics, which partitions an infinite number of finite-length trajectories into a finite number of trajectory sets, describes the dynamics of a system in a simplified and coarse-grained way with a limited number of symbols. The study of symbolic dynamics in 1D chaotic map has been further developed and is named as the applied symbolic dynamics. In this paper, we will study the applied symbolic vector dynamics of CML. Based on the original contribution proposed in Refs.[6], we will study the ergodic property of CML. We will analyze the relation between admissibility condition and control parameters, and then give a coupling coefficient estimation method based on the ergodic property. Both theoretical and experimental results show that we provide a natural analytical technique for understanding turbulences in CML. Many of our findings could be expanded to a wider range of application.

nlin.CD↗

arXiv2008

Neutrino Masses and the LHC: Testing Type II Seesaw

We demonstrate how to systematically test a well-motivated mechanism for neutrino mass generation (Type-II seesaw) at the LHC, in which a Higgs triplet is introduced. In the optimistic scenarios with a small Higgs triplet vacuum expectation value vd < 10^{-4} GeV, one can look for clean signals of lepton number violation in the decays of doubly charged and singly charged Higgs bosons to distinguish the Normal Hierarchy (NH), the Inverted Hierarchy (IH) and the Quasi-Degenerate (QD) spectrum for the light neutrino masses. The observation of either H+ --> tau+ nubar or H+ --> e+ nubar will be particularly robust for the spectrum test since they are independent of the unknown Majorana phases. The H++ decays moderately depend on a Majorana phase Phi2 in the NH, but sensitively depend on Phi1 in the IH. In a less favorable scenario vd > 2 10^{-4} GeV, when the leptonic channels are suppressed, one needs to observe the decays H+ --> W+ H_1 and H+ --> t bbar to confirm the triplet-doublet mixing which in turn implies the existence of the same gauge-invariant interaction between the lepton doublet and the Higgs triplet responsible for the neutrino mass generation. In the most optimistic situation, vd approx 10^{-4} GeV, both channels of the lepton pairs and gauge boson pairs may be available simultaneously. The determination of their relative branching fractions would give a measurement for the value of vd.

hep-ph↗

arXiv2007

Pseudo-random number generator based on asymptotic deterministic randomness

An approach to generate the pseudorandom-bit sequence from the asymptotic deterministic randomness system is proposed in this Letter. We study the characteristic of multi-value correspondence of the asymptotic deterministic randomness constructed by the piecewise linear map and the noninvertible nonlinearity transform, and then give the discretized systems in the finite digitized state space. The statistic characteristics of the asymptotic deterministic randomness are investigated numerically, such as stationary probability density function and random-like behavior. Furthermore, we analyze the dynamics of the symbolic sequence. Both theoretical and experimental results show that the symbolic sequence of the asymptotic deterministic randomness possesses very good cryptographic properties, which improve the security of chaos based PRBGs and increase the resistance against entropy attacks and symbolic dynamics attacks.

nlin.CD↗

arXiv2007

Pair Production of Doubly-Charged Scalars: Neutrino Mass Constraints and Signals at the LHC

We study the pair production of doubly charged Higgs bosons at the Large Hadron Collider (LHC), assuming the doubly charged Higgs to be part of an SU(2)_L triplet which generates Majorana masses for left-handed neutrinos. Such pair-production has the advantage that it is not constrained by the triplet vacuum expectation value, which tends to make the single production rate rather small. We point out that, in addition to the Drell-Yan (DY) production mechanism, two-photon processes also contribute to H++H++ production at a level comparable to the QCD corrections to the DY channel. Decays of the doubly charged Higgs into both the l+l+ and W+W+ modes are studied in detail to optimize the signal observation over the backgrounds. Doubly charged scalars should be observable at the LHC with 300 fb^-1 integrated luminosity in the ll channel upto the mass range of 1 TeV even with a branching fraction of about 60 %, and in the WW channel upto a mass of 700 GeV. Such a doubly charged Higgs, if it is a member of a triplet generating neutrino masses,cannot be long-lived on the scale of collider detectors although it might lead to a displaced secondary vertex during its decay if it is lighter than about 250 GeV.

hep-ph↗