We make a full tree level study of the signatures of anomalous gauge couplings of the Higgs boson at the CERN LHC via the semileptonic decay mode in WW scatterings. Both signals and backgrounds are studied at the hadron level for the Higgs mass in the range 115 GeV to 200 GeV. We carefully impose suitable kinematical cuts for suppressing the backgrounds. To the same sensitivity as in the pure leptonic mode, our result shows that the semileptonic mode can reduce the required integrated luminosity by a factor of 3. If the anomalous couplings in nature are actually larger than the sensitivity bounds shown in the text, the experiment can start the test for an integrated luminosity of 50 inverse fb.
We present predictions for the inclusive production of charmed hadrons at the CERN LHC in the general-mass variable-flavor-number scheme at next-to-leading order. Detailed numerical results are compared to data where available, or presented in a way to ease future comparisons with experimental results. We also point out that measurements at large rapidity have the potential to pin down models of intrinsic charm.
Potential of the LHC to determine the electromagnetic couplings of the $τ$ lepton is discussed via the process ${γγ\to τ^{+}τ}^{-}$. Highly improved constraints of the anomalous magnetic and electric dipole moments have been obtained compared to the LEP sensitivity.
We study the potential of the exclusive $pp\to p\ell^-\ell^+p$ process to probe excited leptons at the LHC which is known to be one of the most clean channel at the hadron colliders. The sensitivity of the model parameters is obtained 95% confidence level by considering three forward detector acceptances; $0.0015< ξ< 0.5$, $0.0015< ξ<0.15$ and $0.1< ξ< 0.5$.
We discuss the potential of the photon-induced two lepton final states at the LHC to explore the phenomenology of the Kaluza-Klein (KK) tower of gravitons in the scenarios of the Arkani-Hamed, Dimopoulos and Dvali(ADD) model and Randall-Sundrum (RS) model. The sensitivity to model parameters can be improved compared to the present LEP or Tevatron sensitivity.
Potential of the LHC to explore the phenomenology of the Kaluza-Klein (KK) tower of gravitons in the scenarios of the Arkani-Hamed, Dimopoulos and Dvali(ADD) model and Randall-Sundrum (RS) model is discussed via the process ${γγ\to γγ}$ including the Standard Model one loop diagram. The improved constraints on model parameters have been obtained compared to the LEP and Tevatron sensitivity.
This work investigates the exclusive photoproduction of $ψ(2S)$ meson off nuclei evaluating the coherent and the incoherent contributions. The theoretical framework used in the present analysis is the light-cone dipole formalism and predictions are done for PbPb collisions at the CERN-LHC energy of 2.76 TeV. A comparison is done to the recent ALICE Collaboration data for the $ψ(1S)$ state photoproduction.
We investigate the sensitivity of top pair production to the properties of different Beyond the Standard Model theories embedding a new neutral boson. We include six-fermion decay, and account for the full tree-level Standard Model ttbar interference, with all intermediate particles allowed off-shell. We focus on those observables best suited to the lepton-plus-jets final state at the LHC, and simulate the resulting experimental conditions, including kinematic requirements and top quark pair reconstruction in the presence of missing transverse energy and combinatorial ambiguity in quark-top as…
We present a simple extension of the standard model (SM) to explain the diphoton excess, reported by CMS and ATLAS at CERN LHC. The SM is extended by a dark sector including a vector-like lepton doublet and a singlet of zero electromagnetic charge, which are odd under a $Z_2$ symmetry. These vector-like leptons assist the additional scalar, different from SM Higgs, to decay to di-photons of invariant mass around 750 GeV and thus explaining the excess observed at LHC. The admixture of neutral component of the vector-like lepton doublet and singlet constitute the dark matter component of the Uni…
The single diffractive cross section for heavy quarks production is calculated in next-no-leading order (NLO) in nucleus-nucleus collisions. Such processes are expected to occur at the LHC. We start using the hard diffractive factorization formalism, taking into account the recent experimental parameterization for the Pomeron Structure Function (DPDF). Absorptive corrections are accounted by the multiple Pomeron contributions considering a gap survival probability, where its theoretical uncertainty for nuclear collisions is discussed. We estimate the diffractive ratios for single diffraction p…
We provide the next-to-leading order (NLO) predictions for the neutralino pair production via quark-antiquark annihilation and gluon-gluon fusion at the CERN Large Hadron Collider, focusing on the lightest neutralino which is likely to be the lightest supersymmetric particle. The dependence of total LO, NLO cross sections, and $K$ factor on the center-of-mass energy, the $M_2$-$μ$ mass plane, the squark mass, and the factorization and renormalization scales is comprehensively analyzed for three different scenarios in the minimal supersymmetric standard model and the constrained minimal supersy…
Current CERN Large Hadron Collider data on the 126 GeV standard model-like Higgs boson suggest the possibility of larger Higgs boson couplings with the weak gauge bosons, $g_{hVV}$, than those in the standard model. We use the Georgi-Machacek model as an explicit model to realize such a scenario. We find that the $g_{hVV}$ couplings can be larger than the standard model value by a factor of about 1.3 maximally in the parameter region consistent with the current Higgs boson search data and allowed by various other constraints. We then show how the modified $g_{hVV}$ couplings lead to enhancemen…
Models based on Universal Extra Dimensions predict Kaluza-Klein (KK) excitations of all Standard Model (SM) particles. We examine the pair production of KK excitations of top- and bottom-quarks at the Large Hadron Collider. Once produced, the KK top/bottom quarks can decay to $b$-quarks, leptons and the lightest KK-particle, $γ_1$, resulting in 2 $b$-jets, two opposite sign leptons and missing transverse momentum, thereby mimicing top-pair production. We show that, with a proper choice of kinematic cuts, an integrated luminosity of 100 fb$^{-1}$ would allow a discovery for an inverse radius up…
Testing a possible W and Z structure at the LHC/CERN
在大型强子对撞机上进行实验分析的首批通道之一是$ p + p \longrightarrow l^+ + l ^- + X $。这个通道中的共振将是一个新的规范中性玻色子的明确指示，正如许多扩展模型所提出的那样。在本文中，我们提请注意的可能性，在这个通道中的新的共振可能有自旋零。一个新的高质量自旋零态可能是标准模型粒子复合性质的有力标志。我们对新假设的重规范粒子的产生和衰变做了自旋零和自旋一的比较，并给出了一些可以很容易地识别它们自旋的分布。
We investigate the photoproduction of $ρ$ mesons in ultraperipheral heavy ion collisions at RHIC and LHC energies in the dipole approach and within two phenomenological models based on the the Color Glass Condensate (CGC) formalism. We estimate the integrated cross section and rapidity distribution for meson production and compare our predictions with the data from the STAR collaboration. In particular, we demonstrate that the total cross section at RHIC is strongly dependent on the energy behavior of the dipole-target cross section at low energies, which is not well determined in the dipole a…
We explore the discovery potential of doubly charged Higgs bosons (ξ^{\pm\pm}) at the CERN Large Hadron Collider (LHC). For moderate values of the coupling constants in the original Type-II seesaw model, these doubly-charged Higgs bosons are not accessible by any present or near future collider experiments. In a gauged B-L symmetric model we introduce two triplet scalars to execute a variant of type-II seesaw at the TeV scale. This leads to a clear like-sign dilepton signal in the decay mode of ξ^{\pm\pm} for a small vacuum expectation value (\lsim 10^5 \eV) of the triplet scalar ξ= (ξ^{++}, ξ…
We analyze the potentiality of hadron colliders to search for large extra dimensions via the production of photon pairs. The virtual exchange of Kaluza--Klein gravitons can significantly enhance this processes provided the quantum gravity scale ($M_S$) is in the TeV range. We studied in detail the subprocesses $q \bar{q} \to γγ$ and $g g \to γγ$ taking into account the complete Standard Model and graviton contributions as well as the unitarity constraints. We show that the Tevatron Run II will be able to probe $M_S$ up to 1.5--1.9 TeV at 2$σ$ level, while the LHC can extend this search to 5.3-…
We study the possibility to test the Type I seesaw mechanism for neutrino masses at the CERN Large Hadron Collider. The inclusion of three generations of right-handed neutrinos (N_i) provides an attractive option of gauging the B-L accidental symmetry in the Standard Model (as well as an extended symmetry X=Y-5(B-L)/4). The production mechanisms for the right-handed neutrinos through the Z' gauge boson in the U(1)_{B-L} and U(1)_X extensions of the Standard Model are studied. We discuss the flavor combinations of the charged leptons from the decays of N_i in the Delta L=2 channels. We find tha…
We discuss production of charmed mesons as well as electrons/muons from semileptonic decays of charm and bottom mesons in proton-proton collisions at the LHC. The cross section for inclusive production of $c \bar c$ and $b \bar b$ pairs is calculated in the framework of the $k_{\perp}$-factorization approach. Here, the KMR and Jung CCFM unintegrated gluon distribution functions are used. Theoretical uncertainties of the model related to the choice of renormalization and factorization scales as well as due to the quark mass are also discussed. The hadronization of charm and bottom quarks is inc…
We apply the leading and sub-leading electroweak (EW) corrections to the Drell-Yan process of the neutralino pair production at proton-proton collision, in order to calculate the effects of the these corrections on the neutralino pair production at the LHC. We provide an analysis of the dependence of the Born cross-sections for $pp\rightarrow\widetildeχ_{i}^{0}\widetildeχ_{j}^{0}$ and the EW corrections to this process, on the center-of-mass energy $\sqrt s$, on the $M_2$-$μ$ mass plane and on the squark mass for the three different scenarios. The numerical results show that the relative corre…
Neutral $Z$ boson pair production due to radion resonance in the Randall-Sundrum model: prospects at the CERN LHC
在大型强子对撞机（LHC）上，由于Radion共振而产生的中性$Z$玻色子对是探索扭曲几何（Randall-Sundrum模型）概念的一个有趣过程。由于迹线异常和顶（夸克）环增强了镭子与一对胶子的耦合，镭子可以提供比任何新物理效应更大的事件率可能性。使用适当的放射性顶-反顶（夸克离壳）耦合，我们得到了正确的Radion生产率在大型强子对撞机和探索的几个特点，较重的Radion衰变成一对真正的$Z$玻色子，随后衰变成带电的$4 l (l=e, μ)$轻子（镀金模式）。使用信号和背景事件率，我们得到了在$5σ$，$10σ$发现水平上的Radion质量$m_ϕ$和Radion vev $\vphi$的界限。
Triple gauge boson associated production at the LHC serves as an interesting channel to test the robustness of the Standard Model. Any deviation from its SM prediction may indicate possible existence of relevant new physics, e.g., anomalous quartic gauge boson couplings. In this paper, a Monte-Carlo feasibility study of measuring WWA production with pure leptonic decays and probing anomalous quartic gauge-boson (e.g., WWAA) couplings, is presented in detail for the first time, with parton shower and detector simulation effects taken into account. Our results show that at the sqrt{s} = 14 TeV L…
Photoproduction of vector mesons are computed in dipole model in proton-proton ultraperipheral collisions(UPCs) at the CERN Large Hadron Collider (LHC). The dipole model framework is employed in the calculations of vector mesons production in diffractive processes. Parameters of the bCGC model are refitted with the latest inclusive deep inelastic scattering experimental data. Employing the bCGC model and Boosted Gaussian light-cone wave function for vector mesons, we obtain prediction of rapidity distributions of $J/ψ$ and $ψ(2s)$ mesons in proton-proton ultraperipheral collisions at the LHC. …
