The apparent excess in the Higgs to di-photon rate at the LHC: New Physics or QCD uncertainties?

The Higgs boson with a mass _MH≈126 GeV$M_H\approx 126\text{GeV}$ has been observed by the ATLAS and CMS experiments at the LHC and a total significance of about five standard deviations has been reported by both collaborations when the channels H→γγ$H\to \gamma \gamma$ and H→ZZ→4?$H\to ZZ\to 4?$ are combined. Nevertheless, while the rates in the later search channel appear to be in accord with those predicted in the Standard Model, there seems to be an excess of data in the case of the H→γγ$H\to \gamma \gamma$ discovery channel. Before invoking new physics contributions to explain this excess in the di-photon Higgs rate, one should verify that standard QCD effects cannot account for it. We describe how the theoretical uncertainties in the Higgs boson cross section for the main production process at the LHC, gg→H$gg\to H$, which are known to be large, should be incorporated in practice. We further show that the discrepancy between the theoretical prediction and the measured value of the gg→H→γγ$gg\to H\to \gamma \gamma$ rate, reduces to about one standard deviation when the QCD uncertainties are taken into account.     

Anomalous Higgs couplings at the LHeC

The discovery of Higgs boson plays a crucial role in understanding the electroweak symmetry breaking sector. From now on, solving the dynamics of this sector needs precision measurements of the couplings of the Higgs boson to the Standard Model particles. In this work, we investigate the constrains on the anomalous HWW   and HWWγ$HWW\gamma$ couplings, described by the dimension-six operators in the effective Lagrangian, in a high energy envisaged ep collider which is called Large Hadron electron Collider (LHeC). We obtained the 95% confidence level limits on the couplings of anomalous HWW   and HWWγ$HWW\gamma$ vertex, with the design luminosity of 10 fb⁻¹$10{\text{fb}}^{-1}$ and electron beam energy of 140 GeV, through ep→νH+X$ep\to \nu H+X$, γp→WH+X$\gamma p\to WH+X$ and eγ→WHν$e\gamma \to WH\nu$ processes by considering the new physics energy scale to be Λ=1 TeV$\Lambda =1\text{TeV}$. The sensitivity of the LHeC to the new physics scale is also briefly discussed.     

On the solvability of the transvection group of extrinsic symplectic symmetric spaces

Let M$M$ be a symplectic symmetric space, and let ?:M→V$?:M\to V$ be an extrinsic symplectic symmetric immersion in the sense of Krantz and Schwachhöfer (2010) [7], i.e., (V,Ω)$(V,\Omega )$ is a symplectic vector space and ?$?$ is an injective symplectic immersion such that for each point p∈M$p\in M$, the geodesic symmetry in p$p$ is compatible with the reflection in the affine normal space at ?(p)$?\left(p\right)$.     

On the parallel transport of the Ricci curvatures

Geometrical characterizations are given for the tensor R⋅S$R\cdot S$, where S$S$ is the Ricci tensor   of a (semi-)Riemannian manifold (M,g)$(M,g)$ and R$R$ denotes the curvature operator   acting on S$S$ as a derivation, and of the Ricci Tachibana tensor  _∧g⋅S${\wedge }_g\cdot S$, where the natural metrical operator  _∧g${\wedge }_g$ also acts as a derivation on S$S$. As a combination, the Ricci curvatures   associated with directions on M$M$, of which the isotropy determines that M$M$ is Einstein, are extended to the Ricci curvatures of Deszcz   associated with directions and planes on M$M$, and of which the isotropy determines that M$M$ is Ricci pseudo-symmetric in the sense of Deszcz.     

Enriching the exploration of the mUED model with event shape variables at the CERN LHC

We propose a new search strategy based on the event shape variables for new physics models where the separations among the masses of the particles in the spectrum are small. Collider signature of these models, characterized by low _pT$p_T$ leptons/jets and low missing _pT$p_T$, are known to be difficult to look for. The conventional search strategies involving hard cuts may not work in such situations. As a case study, we have investigated the hitherto neglected jets + missing _ET$E_T$ signature – known to be a challenging one – arising from the pair productions and decay of n=1$n=1$ KK-excitations of gluons and quarks in the minimal Universal Extra Dimension (mUED) model. Judicious use of the event shape variables enables us to reduce the Standard Model backgrounds to a negligible level. We have shown that in mUED, R⁻¹$R^{-1}$ up to 850 GeV$850\text{GeV}$ can be explored or ruled out with 12 fb⁻¹ of integrated luminosity at the 7 TeV run of the LHC. We also discuss the prospects of employing these variables for searching other beyond Standard Model physics with compressed or partially compressed spectra.     

Search for lepton flavor violation in supersymmetric models via meson decays

Considering the constraints from the experimental data on μ→eγ$\mu \to e\gamma$, μ→3e$\mu \to 3e$, μ–e$\mu \text{–}e$ conversion, etc., we analyze the lepton flavor violating decays ?(J/Ψ,?(1S))→e⁺μ⁻(μ⁺τ⁻)$?(J/\Psi ,?(1S))\to e^{+}{\mu }^{-}({\mu }^{+}{\tau }^{-})$ in the scenarios of the minimal supersymmetric extensions of Standard Model with seesaw mechanism. Numerically, there is parameter space that the LFV processes of J/Ψ(?)→μ⁺τ⁻$J/\Psi (?)\to {\mu }^{+}{\tau }^{-}$ can reach the upper experimental bounds, meanwhile the theoretical predictions on μ→eγ$\mu \to e\gamma$, μ→3e$\mu \to 3e$, μ–e$\mu \text{–}e$ conversion satisfy the present experimental bounds. For searching of new physics, lepton flavor violating processes J/Ψ(?)→μ⁺τ⁻$J/\Psi (?)\to {\mu }^{+}{\tau }^{-}$ may be more promising and effective channels.     

Uniqueness of balanced metrics on holomorphic vector bundles

Let E→M$E\to M$ be a holomorphic vector bundle over a compact Kähler manifold (M,ω)$(M,\omega )$. We prove that if E$E$ admits a ω$\omega$-balanced metric (in X. Wang’s terminology (Wang, 2005 [3])) then it is unique. This result together with Biliotti and Ghigi (2008) [14] implies the existence and uniqueness of ω$\omega$-balanced metrics of certain direct sums of irreducible homogeneous vector bundles over rational homogeneous varieties. We finally apply our result to show the rigidity of ω$\omega$-balanced Kähler maps into Grassmannians.     

A study on the relations between the topological parameter and entanglement

In this Letter, some relations between the topological parameter d   and concurrences of the projective entangled states have been presented. It is shown that for the case with d=n$d=n$, all the projective entangled states of two n  -dimensional quantum systems are the maximally entangled states (i.e. C=1$C=1$). And for another case with d≠n$d\ne n$, C   both approach 0 when d→+∞$d\to +\infty$ for n=2$n=2$ and 3. Then we study the thermal entanglement and the entanglement sudden death (ESD) for a kind of Yang–Baxter Hamiltonian. It is found that the parameter d   influences not only the critical temperature _Tc$T_c$ but also the maximum entanglement value that the system can arrive at. And we also find that the parameter d has a great influence on the ESD.     

On leafwise conformal diffeomorphisms

For every diffeomorphism φ:M→N$\phi :M\to N$ between 3-dimensional Riemannian manifolds M$M$ and N$N$, there are locally two 2-dimensional distributions _D±$D_{\pm }$ such that φ$\phi$ is conformal on both of them. We state necessary and sufficient conditions for a distribution to be one of _D±$D_{\pm }$. These are algebraic conditions expressed in terms of the self-adjoint and positive definite operator induced from _φ∗${\phi }_{\ast }$. We investigate the integrability condition of _D+$D_{+}$ and _D−$D_{-}$. We also show that it is possible to choose coordinate systems in which leafwise conformal diffeomorphism is holomorphic on leaves.     

Implications of neutrino mass generation from QCD confinement

We consider the possibility that the quark condensate formed by QCD confinement generates Majorana neutrino masses mν$m_{\nu }$ via dimension seven operators. No degrees of freedom beyond the Standard Model are necessary, below the electroweak scale. Obtaining experimentally acceptable neutrino masses requires the new physics scale Λ∼TeV$\Lambda \sim \text{TeV}$, providing a new motivation for weak-scale discoveries at the LHC. We implement this mechanism using a Z₃$Z_3$ symmetry which leads to a massless up quark above the QCD chiral condensate scale. We use non-helicity-suppressed light meson rare decay data to constrain Λ. Experimental constraints place a mild hierarchy on the flavor structure of dimension seven operators and the resulting neutrino mass matrix.     

Critical behavior of the absorbing state transition in the contact process with relaxing immunization

We introduce a model for the Contact Process with relaxing immunization CPRI  . In this model, local memory is introduced by a time and space dependence of the contamination probability. The model has two parameters: a typical immunization time τ$\tau$ and a maximum contamination probability a$a$. The system presents an absorbing state phase transition whenever the contamination probability a$a$ is above a minimum threshold. For short immunization times, the system evolves to a statistically stationary active state. Above _τc(a)${\tau }_c\left(a\right)$, immunization predominates and the system evolves to the absorbing vacuum state. We employ a finite-size scaling analysis to show that the transition belongs to the standard directed percolation universality class. The critical immunization time diverges in the limit of a→1$a\to 1$. In this regime, the density of active sites decays exponentially as τ$\tau$ increases, but never reaches the vacuum state in the thermodynamic limit.     

FCNC-induced heavy-quark events at the LHC from supersymmetry

We analyze the production and subsequent decay of the neutral Higgs bosons h≡h⁰,H⁰,A⁰$h\equiv h^0,H^0,A^0$ of the MSSM into electrically neutral quark pairs of different flavors (qq^′≡tc,bs$q{q}^{\prime }\equiv tc,bs$, depending on h  ) at the LHC, i.e. σ(pp→h→qq^′)$\sigma (pp\to h\to q{q}^{\prime })$, and compare with the direct FCNC production mechanisms σ(pp→qq^′)$\sigma (pp\to q{q}^{\prime })$. The cross-sections are computed in the unconstrained MSSM with minimal flavor-mixing sources and taking into account the stringent bounds from b→sγ$b\to s\gamma$. We extend the results previously found for these FCNC processes, which are singularly uncommon in the SM. Specifically, we report here on the SUSY-EW part of σ(pp→h→qq^′)$\sigma (pp\to h\to q{q}^{\prime })$ and the SUSY-QCD and SUSY-EW contributions to σ(pp→bs)$\sigma (pp\to bs)$. In this way, the complete map of MSSM predictions for the qq^′$q{q}^{\prime }$-pairs produced at the LHC becomes available. The upshot is that the most favorable channels are: (1) the Higgs boson FCNC decays into bs, and (2) the direct production of tc   pairs, both of them at the ∼1 pb$\sim 1\text{pb}$ level and mediated by SUSY-QCD effects. If, however, the SUSY-QCD part is suppressed, we find a small SUSY-EW yield for σmax_{(pp→h→tc)}∼¹⁰⁻⁴ pb$\sigma {(pp\to h\to tc)}_{\max }\sim {10}^{\mathrm{-4}}\text{pb}$ but, at the same time, σmax_{(pp→h→bs)}∼0.1–1 pb$\sigma {(pp\to h\to bs)}_{\max }\sim 0.1\text{–}1\text{pb}$, which implies a significant number (∼¹⁰⁴–¹⁰⁵$\sim {10}^4\text{–}{10}^5$) of bs   pairs per 100 fb⁻¹$100{\text{fb}}^{\mathrm{-1}}$ of integrated luminosity.     

The high temperature expansion of the classical XYZ chain

The β$\beta$-expansion of the Helmholtz free energy (HFE) up to order β¹²${\beta }^{12}$ of the classical XYZ model with a single-ion anisotropy term and external magnetic field is calculated and compared to the numerical solution of Joyce's [Phys. Rev. Lett. 19 (1967) 581] for the XXZ   classical model, with neither single-ion anisotropy term nor external magnetic field. This comparison shows that the derived analytical expansion is valid for intermediate temperatures such as kT/_Jx≈0.5$\mathit{kT}/J_x\approx 0.5$. The specific heat and magnetic susceptibility of the S=2$S=2$ antiferromagnetic chain can be approximated by their respective classical results, within an error of 2.5%$2.5\%$, up to kT/J≈0.8$\mathit{kT}/J\approx 0.8$. For a vanishing external magnetic field the ferromagnetic and antiferromagnetic chains are shown to have the same classical HFE; their behaviour in a non-vanishing external magnetic field is also described.     

On m-accretive Schrödinger-type operators with singular potentials on Riemannian manifolds

We consider a Schrödinger-type differential expression _HV=∇^∗∇+V$H_V={\nabla }^{\ast }\nabla +V$, where ∇$\nabla$ is a Hermitian connection on a Hermitian vector bundle E$E$ over a complete Riemannian manifold (M,g)$(M,g)$ with metric g$g$ and positive smooth measure dμ$d\mu$, and V$V$ is a locally integrable section of the bundle of endomorphisms of E$E$. We give a sufficient condition for m$m$-accretivity of a realization of _HV$H_V$ in L²(E)$L^2\left(E\right)$.