One-loop gg\to b\bar{b} effects in the main irreducible background to exclusive H\to b\bar{b} production at the LHC

We calculate the amplitude of $gg\to b\bar{b}$ production for the colour singlet, J _z =0, di-gluon state at $\mathcal{O}(\alpha_{\mathrm{S}}^{2})$ order. We consider the cancellation and a realistic cut-off, of the infrared divergent terms. We show that the one-loop radiative QCD contributions effectively reduce the Born level result for the central exclusive $b\bar{b}$ cross section at the LHC. This process is essentially the only irreducible QCD background to the exclusive $H\to b\bar{b}$ signal.     

A 480 ms isomeric 29/2−-state of the(p_{1/2}^{ - 2} )_{0^ + } f_{5/2}^{ - 1} (i_{13/2}^{ - 2} )_{12^ + } configuration in203Pb

A new, 480 ms, 29/2^? isomeric level has been found in²⁰³Pb at an excitation energy of 2950.1 keV by bombarding²⁰⁴Hg with α-particles in the energy range 45–55 MeV using the Stockholm 225-cm cyclotron. This 29/2^? state is suggested to be mainly due to the configuration (p ₁ ^2/?2 f ₅ ^2/?1 i ₁₃ ^2/?2 )₁₂. The 29/2^? state decays predominantly by a 153.4 keV M2 transition to a 23/2^? level and by a 1027.5 keV M4 transition to a 21/2⁺ level, followed by two E2 transitions of energies 258.6 keV and 838.7 keV, respectively, to the previously known 13/2⁺, 6.4 s isomeric level. The decay scheme of the 29/2^? isomeric state is based on experimental information obtained from total and delayedγ-ray intensities,γγ-coincidences, excitation functions, lifetime and delayed conversion electron measurements. The presence of the 29/2^? level confirms an essential and expected feature of the shell model for five neutron holes added to the²⁰⁸Pb-core.     

Determining the η−η′ mixing by the newly measured \mathit{BR}(D(D_{s})\to\eta(\eta')+\bar{l}+\nu_{l}

The mixing of η?η′ or η?η′?G is of a great theoretical interest, because it concerns many aspects of the underlying dynamics and hadronic structure of pseudoscalar mesons and glueball. Determining the mixing parameters by fitting data is by no means trivial. In order to extract the mixing parameters from the available processes where hadrons are involved, theoretical evaluation of hadronic matrix elements is necessary. Therefore model dependence is somehow unavoidable. In fact, it is impossible to extract the mixing angle from a unique experiment because the model parameters must be obtained by fitting other experiments. Recently $\mathit{BR}(D\to\eta+\bar{l}+\nu_{l})$ and $\mathit{BR}(D_{s}\to\eta(\eta')+\bar{l}+\nu_{l})$ have been measured, thus we are able to determine the η?η′ mixing solely from the semileptonic decays of D-mesons where contamination from the final state interactions is absent. Thus we hope that the model dependence of the extraction can be somehow alleviated. Once $\mathit{BR}(D\to\eta'+\bar{l}+\nu_{l})$ is measured, we can further determine all the mixing parameters for η?η′?G. As more data are accumulated, the determination will be more accurate. In this work, we obtain the transition matrix elements of D _(s)→η ^(′) using the light-front quark model whose feasibility and reasonability for such processes have been tested.     

Contribution of a heavy singlet quark to the mass differences \Delta m_{K^o } , \Delta m_{B_d } , and \Delta m_{B_s } and to the CP-violation parameter ɛ K

It is shown that, within the Standard Model extended by including a singlet quark heavy enough to prevent its direct detection at LHC, the mass differences $ \Delta m_{B_d } $ and $ \Delta m_{B_s } $ and the parameter of CP violation in K-meson oscillations, ? _K , acquire universal corrections of about 5 to 10%. Implicit experimental constraints on the mass of this new quark are discussed.     

Data on Neutron–Neutron Scattering Length from the Reaction $$\boldsymbol{n+^{2}\textrm{H}\to n+n+p}$$ at $$\boldsymbol{E_{n}=60}$$ MeV

Physics of Atomic Nuclei - The $${}^{1}S_{0}$$ neutron–neutron ( $$nn$$ ) scattering length was measured in the neutron–deuteron ( $$nd$$ ) breakup reaction at an energy of 60 MeV. The...     

t\bar{t}H\to t\bar{t}\tau^{+}\tau^{-} —toward the measurement of the top-Yukawa coupling

One of the main goals of the ATLAS experiment is to measure various Higgs boson couplings as accurately as possible. Such a measurement is mandatory for a full understanding of the Higgs sector. One of the most challenging measurements of the Higgs boson properties is the determination of the Yukawa coupling to the top quark. To complement the $t\bar {t}H\rightarrow t\bar {t}\ensuremath {\mathit {b}\bar {\mathit {b}}}$ channel, which is the most significant in the low Higgs mass region (m _H ～120 GeV), we introduce a feasibility study of the $t\bar {t}H$ channel with the Higgs decaying to a pair of τ leptons. The signal events were reconstructed using the full and the fast simulation of the ATLAS detector. It is shown that both the distributions and the number of expected events after the same cuts agree, and that we can use the fast simulation to complete the analysis. We obtain a significance of 1.6σ for the low luminosity condition (30 fb^?1) and m _H =120 GeV, and 2.0σ for the high luminosity condition (300 fb^?1) and m _H =120 GeV. The observability of Higgs boson in this channel is demonstrated to be very marginal, even in the absence of taking into account $t\bar {t}+\mathrm{jets}$ .     

{SL(2, \mathbb{C})} Chern–Simons Theory and the Asymptotic Behavior of the Colored Jones Polynomial

It has been proposed that the asymptotic behavior of the colored Jones polynomial is equal to the perturbative expansion of the Chern–Simons gauge theory with complex gauge group ${SL(2, \mathbb{C})}$ on the hyperbolic knot complement. In this note we make the first step toward verifying this relation beyond the semi-classical approximation. This requires a careful understanding of some delicate issues, such as normalization of the colored Jones polynomial and the choice of polarization in Chern–Simons theory. Addressing these issues allows us to go beyond the volume conjecture and to verify some predictions for the behavior of the subleading terms in the asymptotic expansion of the colored Jones polynomial.     

On the two-loop $$ \ma thcal{O} $$( αs2) correc tions to the pole mass of the t quark in the MSSM

The paper is devoted to the calculation of two-loop (α _s ²) MSSM corrections to the relation between the pole mass of the t quark and its running mass in the scheme. Firstly, the value of the second-order contribution from large-mass expansion in mt/M _SUSY is studied. Contrary to our expectations, this contribution turned out to be negligible. As a by-product of this calculation, the two-loop anomalous dimension of the running quark mass is obtained in the supersymmetric QCD. Secondly, the influence of the two-loop corrections to the t-quark mass on the predicted superpartner masses is investigated. The text was submitted by the authors in English.     

Back to the Amitsur–Levitzki Theorem: a Super Version for the Orthosymplectic Lie Superalgebra $${\mathfrak{o}}{\mathfrak{s}}{\mathfrak{p}}\left( {1,2n} \right)$$

We prove an Amitsur–Levitzki type theorem for the Lie superalgebras $\mathfrak{o}\mathfrak{s}\mathfrak{p}\left( {1,2n} \right)$ ) inspired by Kostant's cohomological interpretation of the classical theorem. We show that the Lie superalgebras $\mathfrak{g}\mathfrak{l}\left( {p,q} \right)$ cannot satisfy an Amitsur–Levitzki type super identity if pq≠0 and conjecture that neither can any other classical simple Lie superalgebra with the exception of $\mathfrak{o}\mathfrak{s}\mathfrak{p}\left( {1,2n} \right)$ .     

Regularity and Existence of Global Solutions to the Ericksen–Leslie System in {\mathbb{R}^2}

In this paper, we first establish the regularity theorem for suitable weak solutions to the Ericksen–Leslie system in \({\mathbb{R}^2}\) . Building on such a regularity, we then establish the existence of a global weak solution to the Ericksen–Leslie system in \({\mathbb{R}^2}\) for any initial data in the energy space, under the physical constraints on the Leslie coefficients ensuring the dissipation of energy of the system, which is smooth away from at most finitely many times. This extends earlier works by Lin et al. (Arch Ration Mech Anal 197:297–336, 2010) on a simplified nematic liquid crystal flow to the general Ericksen–Leslie system.     

Sum rule estimate of the subleading non-perturbative contributions to Bs–$\bar{ B}_{s}$ mixing

We use QCD sum rules to compute the matrix elements of the ΔB=2 operators appearing in the heavy-quark expansion of the width difference of the B _s mass eigenstates. The main focus of our analysis is on the subleading operators R ₂ and R ₃, which appear at next-to-leading order in the 1/m _b expansion. The matrix elements of these operators are already essential for precise phenomenology, but their calculation in lattice QCD is lacking and the values given here provide a first estimate of their values. We conclude that the violation of the factorization approximation for these matrix elements due to non-perturbative vacuum condensates is as low as 1–2%.     

A complete $\mathcal{O}(\alpha_{\mathrm{S}}^{2})$ calculation of the signal–background interference for the Higgs diphoton decay channel

We analyze a noncommutative model of BTZ spacetime based on deformation of the standard symplectic structure of phase space, i.e., a modification of the standard commutation relations among coordinates and momenta in phase space. We find a BTZ-like solution that is nonperturbative in the non-trivial noncommutative structure. It is shown that the use of deformed commutation relations in the modified non-canonical phase space eliminates the horizons of the standard metric.     

In {2 2} vacuums,the null-datum on null rays is exactlyr −5

It is shown, by a simple argument, that in any {2 2} (i.e. type D) vacuum space-time, the complex component of the Weyl curvature (spinor abcd) along any light ray is precisely proportional tor ^–5, wherer is the standard Schwarzschild radial coordinate, or its natural complex generalization for the arbitrary {2 2} case.     

Extending $\mathcal{P}\mathcal{T}$ Symmetry from Heisenberg Algebra to E2 Algebra

The E2 algebra has three elements, J, u, and v, which satisfy the commutation relations [u,J]=iv, [v,J]=−iu, [u,v]=0. We can construct the Hamiltonian H=J ²+gu, where g is a real parameter, from these elements. This Hamiltonian is Hermitian and consequently it has real eigenvalues. However, we can also construct the PT\mathcal{P}\mathcal{T}-symmetric and non-Hermitian Hamiltonian H=J ²+igu, where again g is real. As in the case of PT\mathcal{P}\mathcal{T}-symmetric Hamiltonians constructed from the elements x and p of the Heisenberg algebra, there are two regions in parameter space for this PT\mathcal{P}\mathcal{T}-symmetric Hamiltonian, a region of unbroken PT\mathcal{P}\mathcal{T} symmetry in which all the eigenvalues are real and a region of broken PT\mathcal{P}\mathcal{T} symmetry in which some of the eigenvalues are complex. The two regions are separated by a critical value of g.     

Properties of the _{69}^{150}{\text{T}}{{\text{m}}_{81}} 6− β-decaying isomer

Decay experiments for ¹⁴⁸Ho 6^? and ¹⁵⁰Tm 6^? were carried out at the GSI On-line mass separator using 5 MeV/A ⁵⁸Ni-beams on ⁹⁴Mo and ⁹⁶Ru targets. Gammaγ-and γX-coincidences established the ¹⁵⁰Tm 6^? decay scheme, and e^? gave firm I^π assignments for ¹⁴⁸Dy and ¹⁵⁰Er levels fed in the decays. It was found that the previously unknown \(6_1^ -\) state in ¹⁵⁰Er receives significant β-strength, which strongly suggests \(\pi {h_{11/2}}\nu s_{1/2}^{ - 1}\) character for the ¹⁵⁰Tm 6^? isomer. The results are discussed in terms of the expected GT strength function. Shell model calculations for the \(\pi h_{11/2}^4\) yrast states are presented.     

Inclusion relations for the spaces L(ℝ), \mathcal{H}\mathcal{K} (ℝ) ∩ \mathcal{B}\mathcal{V} (ℝ), and L 2(ℝ)

The inclusion relations for the spaces $ \mathcal{H}\mathcal{K} $ (I), L(I), $ \mathcal{H}\mathcal{K} $ (I) ∩ $ \mathcal{B}\mathcal{V} $ (I), and L ²(I) are found. On unbounded intervals, functions in $ \mathcal{H}\mathcal{K} $ (I) ∩ $ \mathcal{B}\mathcal{V} $ (I) need not be Lebesgue integrable.     

O(α s ) corrections to the polar angle dependence of the longitudinal spin–spin correlation asymmetry in e^{+}e^{-}\to q\bar{q}

We provide analytical results for the O(α _s ) corrections to the polar angle dependence of the longitudinal spin–spin correlation asymmetry in $e^{+}e^{-}\to q\bar{q}$ . For top quark pair production the O(α _s ) corrections to the longitudinal spin–spin asymmetry are strongly polar angle dependent and can amount up to ?4% in the q ²-range from above $t\bar{t}$ threshold up to $\sqrt{q^{2}}=1000\ \mbox {GeV}$ . The O(α _s ) radiative corrections to the correlation asymmetry are below ≈1% in the forward direction where the cross section is largest. In the $e^{+}e^{-}\to b\bar{b}$ case the O(α _s ) corrections reduce the asymmetry value from its m _b =0 value of ?100% to approximately ?96% for q ²-values around the Z peak and are practically independent of the value of the polar angle θ. This reduction can be traced to finite anomalous contributions from residual mass effects which survive the m _b →0 limit. We discuss the role of the anomalous contributions and the pattern of how they contribute to spin-flip and non-flip terms.     

Superconductivity in the doped “pseudo-ladder” compound CaCu$_\mathsf{2}$O$_\mathsf{3}$

An effective anisotropic t-J model for the pseudo-ladder compound CaCu₂O₃ is proposed based on recent experimental studies and band structure calculations. Superconducting pairing mediated by the exchange interaction in the model is investigated as a function of doping away from the antiferromagnetic insulating state. It is shown that strong anisotropy in the electronic spectrum suppresses superconducting temperature in comparison with conventional copper-oxide superconductors with square lattices.     

The Introduction to the ECRH System of the HL-2A Tokamak

The 1 MW/68 GHz/1 s ECRH system of HL-2A device is being designed or fabricated. The O mode wave beams are injected into plasma from low field side of the HL-2A tokomak. Because the EC wave can heat plasma locally, it is a very versatile scheme which has been employed to heating, current drive, profile control, confinement improvement. Up to now, the basic physical and engineering parameters of the whole system have been fixed and the subsystems are being designed or fabricated.