119203542
New physics signals in longitudinal gauge boson scattering at the LHC
We introduce a novel technique designed to look for signatures of new physics in vector boson fusion processes at the TeV scale. This functions by measuring the polarization of the vector bosons to determine the relative longitudinal to transverse production. In studying this ratio we can directly probe the high energy E2-growth of longitudinal vector boson scattering amplitudes characteristic of models with non-Standard Model (SM) interactions. We will focus on studying models parameterized by an effective Lagrangian that include a light Higgs with non-SM couplings arising from TeV scale new physics associated with the electroweak symmetry breaking, although our technique can be used in more general scenarios. We will show that this technique is stable against the large uncertainties that can result from variations in the factorization scale, improving upon previous studies that measure cross section alone.
15862693
Application of Jet Trimming in Boosted Higgs Search
We present the study of the $WH$ and $ZH$ search with the Higgs Boson decayed to $b\bar{b}$ at the Large Hadron Collider. The Higgs Boson and the Vector Boson are required to be boosted, and the Higgs Boson is reconstructed with Jet Trimming Technique. The statistical significance for 30$fb^{-1}$ data is 4.5 $\sigma$, which is comparable to the previous result.
119188665
Data driven search in the displaced $ b\overline{b} $ pair channel for a Higgs boson decaying to long-lived neutral particles
A bstractThis article presents a proposal for a new search channel for the Higgs boson decaying to two long-lived neutral particles, each of which decays to $ b\overline{b} $ at a displaced vertex. The decay length considered is such that the decay takes place within the LHC beampipe. We present a new data-driven analysis using jet substructure and properties of the tracks from the highly-displaced vertices. We consider a model with a 125 GeV Higgs boson with a significant branching fraction to decay via this mode, with the long-lived neutral particle having a mass in the range of 15-40 GeV and a decay length commensurate with the beam pipe radius. Such a signal can be readily observed with an integrated luminosity of 19.5 fb−1 at 8 TeV at the LHC.
14207161
Saturation and Wilson line distributions
We introduce a Wilson line distribution function ${W}_{\ensuremath{\tau}}(v)$ to study gluon saturation at small Feynman ${x}_{F},$ or large $\ensuremath{\tau}=\mathrm{ln}{(1/x}_{F}).$ This new distribution can be obtained from the distribution ${W}_{\ensuremath{\tau}}(\ensuremath{\alpha})$ of the color glass condensate model and the Jalilian-Marian\char21{}Iancu\char21{}McLerran\char21{}Weigert\char21{}Leonidov\char21{}Kovner (JIMWLK) renormalization group equation. ${W}_{\ensuremath{\tau}}(v)$ is physically more relevant, and mathematically simpler to deal with because of unitarity of the Wilson line $v.$ A JIMWLK equation is derived for ${W}_{\ensuremath{\tau}}(v);$ its properties are studied. These properties are used to complete Mueller's derivation of the JIMWLK equation, though for ${W}_{\ensuremath{\tau}}(v)$ and not ${W}_{\ensuremath{\tau}}(\ensuremath{\alpha}).$ They are used to derive a generalized Balitsky-Kovchegov equation for higher multipole amplitudes. They are also used to compute the unintegrated gluon distribution at ${x}_{F}=0,$ yielding a completely flat spectrum in transverse momentum squared ${\mathbf{k}}^{2},$ with a known height. This is similar but not identical to the mean field result at small ${\mathbf{k}}^{2}.$
12305729
Can a chaotic solution in the QCD evolution equation restrain high-energy collider physics?
We indicate that the random aperiodic oscillation of the gluon distributions in a modified Balisky–Fadin–Kuraev–Lipatov (BFKL) equation has positive Lyapunov exponents. This first example of chaos in QCD evolution equations, raises the sudden disappearance of the gluon distributions at a critical small value of the Bjorken variable x and may stop the increase of the new particle events in an ultra high energy hadron collider. PACS numbers: 12.38.Bx, 24.85.+p keywords: QCD evolution equation; Chaos The gluon distributions are important knowledge in research of high energy collider physics. The gluon distributions of the nucleon cannot be extracted directly from the measured structure functions in deep inelastic scattering experiments and they are mainly predicted by using the QCD evolution equations. However, the linear Dokshitzer-GribovLipatov-Altarelli-Parisi (DGLAP) and Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution equations are no longer reliable at ultra higher energy, therefore a series nonlinear evolution equations, for example, the GLR-MQ-ZRS Gribov-Levin-Ryskin, Mueller-Qiu, Zhu-Ruan-Shen (GLR-MQ-ZRS) and Balitsky-Kovchegov (BK) equations were proposed, in which the corrections of the gluon fusion are considered. An important prediction of these equations is that the gluon distributions approach to a so-called ‘saturation limit’ asymptotically at small Bjorken variable x, where gluon splitting is balanced with fusion. As we well know, the nonlinear dynamics may have a characteristic solution–chaos, which have been observed in many natural phenomena. Therefore, it is interesting to ask: Does nonlinear QCD evolution equation of gluon distribution also have chaotic solution? How does it impact the gluon distribution? Recently, we have proposed a nonlinear modified BFKL (MD-BFKL) equation in Ref. [9], which describes the corrections of the gluon recombination to the BFKL equation. We found that the unintegrated gluon distribution function F (x, k) in the MD-BFKL equation in the fixed coupling approximation begins its smooth evolution under suppression of the gluon fusion likes the solution of the BK equation, but when x comes to a smaller critical xc, F (x, k ) will oscillate aperiodically near the evolution endpoint k 0. This behavior has the characteristic feature of chaos: random and sensitive to the initial conditions. Furthermore, with the enhancement of oscillation, the distribution F (x, k) will disappear suddenly at xc. This kind of phase transition led by chaotic solutions will certainly call our attention to reconsider the future of high energy collider physics carefully. In this letter, we indicate that the above-mentioned oscillate solution in the MD-BFKL equation is really chaos and it still holds in the running coupling case.
124251483
Valence quark mixing contribution to the Gottfried sum rule
We have discussed the effect of valence quark mixing in DIS process. This effect, together with the pion cloud effect, dominates the violation of Gottfried sum rule.
18398117
A Dynamical model for nuclear structure functions
We construct a dynamical model for the parton distributions in a nucleus by perturbative evolution of input distributions from a low starting scale. These input distributions are obtained by modifications of the corresponding free nucleon ones; the modifications being determined by standard nuclear physics considerations. The model gives good agreement with existing data. Its extension to the spin dependent case enables an estimation of nuclear modifications to asymmetries observed in recent doubly polarised deep inelastic scattering experiments. Although the structure functions themselves are very different from the free nucleon ones, their ratio is insensitive to these changes.
6805175
Properties of the gluon recombination functions
The gluon recombination functions in the twist-4 QCD evolution equations are studied at the leading logarithmic approximation using both the covariant and non-covariant methods. We justify that the infrared singularities in the twist-4 coefficient functions impede us to simply separate the QCD evolution kernels from the coefficient functions at the equivalent particle approximation. In particulary, we point out that the gluon recombination functions in the GLR-MQ evolution equation are unavailable. The methods avoiding the IR divergences are discussed, which can be used in the derivations of the evolution kernels and coefficient functions at the higher twist level.