An Investigation of Signal Kinematical Region to Study Standard Model Higgs Boson Properties in the H → WW* → ℓvℓv Decay Channel in the ATLAS Experiment at the Large Hadron Collider at 13 TeV

A signal kinematical region is analyzed by the Higgs Boson Working Group (HWW) within the framework of a study of the Standard Model Higgs boson properties in the H → WW* → evεv decay channel in the ATLAS experiment on the Large Hadron Collider (LHC). The analysis is based on the full statistics of proton-proton collision data during exposures in 2015–2016 at the center-of-mass energy of 13 TeV. As compared to our previous analysis, the reconstruction software is updated and the simulation accuracy of backgrounds is improved. Events taken at low and high LHC luminosity are studied separately. In addition, the kinematics at the later stages of event selection is investigated in detail and systematic uncertainties are fully estimated. It is shown that the Monte Carlo modeling satisfactorily describes the experimental data at different selection stages. Kinematic distributions for hadron jets are studied also in the Z-boson control region, where the acquired data reach the order of ten million events. As compared to the previous investigation, the modeling accuracy of Z and background processes is noticeably improved, and events at low and high LHC luminosities are studied separately. Furthermore, all systematic uncertainties related to jets are estimated as well. As a whole, good agreement between experimental results and Monte Carlo simulation data is observed. No problems that would be caused by high luminosity are observed.

     

Radiative corrections in K→π ℓ + ℓ − decays

We calculate radiative corrections to the flavor-changing neutral current process K→π ? ⁺ ? ^?, both for charged and neutral kaon decays. While the soft-photon approximation is shown to work well for the muon channels, we discuss the necessity of further phase space cuts with electrons in the final state. It is also shown how to transfer our results to other decays such as η→γ ? ⁺ ? ^? or ω→π ⁰ ? ⁺ ? ^?.     

Analysis of Bc→τvτ at CEPC

Precise determination of the Bc → tvt branching ratio provides an advantageous opportunity for under-standing the electroweak structure of the Standard Model,me...     

Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.     

Study of D±s→μ±vμ at Belle

We present a preliminary measurement of the B(Ds→μvμ) with the Belle experiment at the KEKB collider. We select Ds→μvμ decays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction. The results are based on a data sample of 550 fb-1 and are compared to similar measurements by other experiments as well as to the predictions of LQCD. We conclude with short prospects for improvements in the accuracy of the measurement.     

Towards B→Vγ decays at NNLO in SCET

We compute NNLO ((α_s ²)) corrections to the hard-scattering kernels entering the QCD factorization formula for B→Vγ decays, where V is a light vector meson. We give complete NNLO results for the dipole operators Q₇ and Q₈, and partial results for Q₁ valid in the large-β₀ limit and neglecting the NNLO correction from hard-spectator scattering. Large perturbative logarithms in the hard-scattering kernels are identified and resummed using soft-collinear effective theory. We use our results to estimate the branching fractions for B→K^*γ and B_s→φγ decays at NNLO and compare them with the current experimental data.     

Proton magnetic resonance spectroscopy in deep human brain structures at 7 T

The increased magnetization and frequency separation at high magnetic field strength, such as 7 T, can provide spectra of high signal-to-noise ratio and spectral resolution. However, most human brain magnetic resonance spectroscopy (MRS) studies at 7 T have employed surface coils and thus limited to superficial brain structures. In this study, volume coil excitation together with volume array reception has been utilized to access deeper brain areas. RF power limitations have been addressed by the use of VERSE-modified pulses, and spectra in parietal and pregenual anterior cingulate cortex (pgACC) have been acquired in eight subjects using STEAM with a short echo time of 20 ms. Spectra were analyzed using LC-model. Therefore, an experimental basis set of in vitro spectra was established from 20 human brain metabolite solutions. An exemplary comparison with an optimized PRESS-based single voxel MRS method at 3 T has been performed. Despite the intrinsically lower signal in STEAM, the 7 T spectra show 1.87 times higher signal-to-noise ratio than at 3 T (using PRESS) and more metabolites could be quantified reliably. The results show that the proposed method can be employed at 7 T in deep brain structures and allows the absolute and relative concentrations of human brain metabolites to be determined with low error levels.     

Collider monojets ofW→τv origin

Within the standard model it is found that the most copious source of events with a single hadronic jet balanced by large missing transverse momentum \((\mathop {p_T }\limits^/ )\) is the decay process \(W \to \tau \bar v \to (n\pi )v\bar v\) . A detailed calculation of the monojet cross-section predicts a lower limit ofO(2) events with \(\mathop {p_T }\limits^/ > 35\) GeV per 100 nb^?1 of integrated luminosity at presently available \(\bar pp\) collider energies.     

Valence Quark Ratio in the Proton

Beginning with precise data on the ratio of structure functions in deep inelastic scattering（DIS） from ³ He and ³ H, collected on the domain 0.19 ≤ xB≤ 0.83, where xBis the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the xB= 1 value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure depen...     

Proton dissociative ρ and elastic φ electroproduction at HERA

The electroproduction of ρ mesons with proton diffractive dissociation for Q ² > 7 GeV² and the elastic electroproduction of φ mesons for Q ² > 6 GeV² are studied in e ⁺ p collisions at HERA with the H1 detector, for an integrated luminosity of 2.8 pb^-1. The dependence of the cross sections on P _t ² and Q ² is measured, and the vector meson polarisation obtained. The cross section ratio between proton dissociative and elastic production of ρ mesons is measured and discussed in the framework of the factorisation hypothesis of diffractive vertices. The ratio of the elastic cross section for φ and ρ meson production is investigated as a function of Q ².     

Spin effects in the dd → 3He n reaction at intermediate energies

The dd → ³He n reaction is considered at the energies between 200 and 520 MeV. The calculations are performed within relativistic multiple scattering model based on the Alt-Grassberger-Sandhas equations. The angular dependences of the differential cross section and vector and tensor analyzing powers are given in comparison with the experimental data.     

Parity Violation in Proton—Deuteron Scattering

JETP Letters - Effects of parity violation in the interaction of relativistic polarized protons and deuterons are discussed. P-odd asymmetries in the total and elastic scattering cross sections, in...     

Polarization of the secondary nucleons in thepp → ppπ 0 andpp→npπ+ reactions at 1000 MeV

The calculation of the secondary nucleons polarization in thepppp⁰ andppnp⁺ reactions at 1000 MeV is effected in the framework of the one-pion exchange model. It is shown that polarization is due to the interference of the resonant amplitude with the non-resonant amplitudes of theN virtual scattering. The angular dependence of the polarization is sensitive to the behaivour of theN scattering amplitudes off the mass shell.Submitted to the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981.     

On the nonperturbative charm effects in inclusive B→X<Subscript>c</Subscript>ℓν decays

We address the nonperturbative effects associated with soft charm quarks in inclusive B decays. Such corrections are allowed by the OPE, but have largely escaped attention so far. The related four-quark ‘double heavy’ expectation values of the form are computed in the 1/m_c expansion by integrating out the charm field to one and two loops. A significant enhancement of the two-loop coefficients is noted. A method is suggested for evaluating the expectation values of the higher-order b quark operators required to calculate charm expectation values, free from the overly large ambiguities of dimensional analyses. The soft charm effects were found generally to be at the level of 0.5% in Γ_sl(b→c); our literal estimate is somewhat smaller as a result of partial cancellations. We propose a direct way to search for such effects in the data. Finally, we discuss the relation of the soft charm corrections in inclusive decays with the ‘intrinsic charm’ ansatz.     

dd → 3 Hen Reaction at Intermediate Energies

The dd → ³ Hen reaction is considered at the energies between 200 and 520?MeV. The Alt–Grassberger–Sandhas equations are iterated up to the lowest order terms over the nucleon–nucleon t-matrix. The parameterized ³ He wave function including five components is used. The angular dependence of the differential cross section and energy dependence of tensor analyzing power T ₂₀ at the zero scattering angle are presented in comparison with the experimental data.     

Phase Transformations α → β → γ → δ → ε in Titanium Hydride TiH x with Increase in Hydrogen Concentration

Structural phase transformations of the hcp bcc fct fcc fct ( ) type in titanium hydrides TiH _x experimentally found to occur with increase in the hydrogen concentration x are studied theoretically. Free energy phases are statistically calculated, and their concentration dependence is determined. Phase transformation temperatures are found from intersection points of free energy curves and from points of common tangents to the curves. The energy parameters of the system are estimated. The calculation results are compared with the experimental data.     

Search for the decay τ− → vτηπ−

We have searched for the decay τ⁻ → v_τηπ⁻ using data accumulated by the ARGUS detector at the e⁺e⁻ storage ring DORIS II at DESY. No η signal was found in the π⁺π⁻π⁰ subsystems of the decay τ⁻ →v_τπ⁻π⁻π⁺ π⁰. We obtain an upper limit for the branching ratio of the decay τ⁻ → v_τηπ⁻ of 1.3% at the 95% confidence level.