arXiv subjects

S. Belogurov

Publications and source records attributed to S. Belogurov.

263 records · Page 15Linked to original sources

arXiv2012

Measurement of b-hadron masses

Measurements of b-hadron masses are performed with the exclusive decay modes B+ -> J/psi K+, B0 -> J/psi K*0, B0 -> J/psi K0S, B0_s -> J/psi phi and Lambda_b -> J/psi Lambda using an integrated luminosity of 35 pb-1 collected in pp collisions at a centre-of-mass energy of 7 TeV by the LHCb experiment. The momentum scale is calibrated with J/psi -> mu+mu- decays and verified to be known to a relative precision of 2 x 10^-4 using other two-body decays. The results are more precise than previous measurements, particularly in the case of the B0_s and Lambda_b masses.

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arXiv2012

Measurement of the effective $B^0_s\rightarrow K^+K^-$ lifetime

A measurement of the effective $B^0_s\rightarrow K^+K^-$ lifetime is presented using approximately $37 pb^{-1}$ of data collected by LHCb during 2010. This quantity can be used to put constraints on contributions from processes beyond the Standard Model in the $B^0_s$ meson system and is determined by two complementary approaches as $τ_{B^0_s\to K^+K^-} = 1.440 \pm 0.096 (stat) \pm 0.008 (syst) \pm 0.003 (model) ps$.

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arXiv2012

First observation of the decay $B^0_s \rightarrow K^{0} \bar{K]^{0}$

The first observation of the decay $\kstarkstar$ is reported using 35\invpb of data collected by LHCb in proton-proton collisions at a centre-of-mass energy of 7 TeV. A total of $49.8 \pm 7.5$ $B^0_s \rightarrow (K^+π^-)(K^-π^+)$ events are {observed within $\pm 50 \mevcc$ of the \Bs mass and $746 \mevcc < m_{Kπ}< 1046 \mevcc$, mostly coming from a resonant $\kstarkstar$ signal.} The branching fraction and the \CP-averaged \Kstarz longitudinal polarization fraction are measured to be {$\BR(\kstarkstar) = (2.81 \pm 0.46 ({\rm stat.}) \pm 0.45 ({\rm syst.}) \pm 0.34\, (f_s/f_d))\times10^{-5}$} and $f_L = 0.31 \pm 0.12 ({\rm stat.}) \pm 0.04 ({\rm syst.})$.

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arXiv2012

First observation of the decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi-

First observations of the Cabibbo suppressed decays B0bar -->D+ K- pi+ pi- and B- --> D0 K- pi+ pi- are reported using 35 pb^{-1} of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo favored decays, from which we obtain B(B0bar --> D+ K- pi+ pi-)/B(B0bar --> D+ pi- pi+ pi-)=(5.9\pm1.1\pm0.5) x 10^{-2} and B(B- --> D0 K- pi+ pi-)/B(B- --> D0 pi- pi+ pi-)=(9.4\pm1.3\pm0.9) x 10^{-2}, where the uncertainties are statistical and systematic, respectively. The B- --> D0 K- pi+ pi- decay is particularly interesting, as it can be used in a similar way to B- --> D0 K- to measure the CKM phase gamma.

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arXiv2012

Search for the rare decays Bs -> mu+ mu- and B0 -> mu+ mu-

A search for the decays Bs -> mu+ mu- and B0 -> mu+ mu- is performed with 0.37 fb^-1 of pp collisions at sqrt{s} = 7 TeV collected by the LHCb experiment in 2011. The upper limits on the branching fractions are BR (Bs -> mu+ mu-) < 1.6 x 10^-8 and BR(B0 -> mu+ mu-) < 3.6 x 10^-9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to BR (Bs -> mu+ mu-) < 1.4 x 10^-8 and BR (B0 -> mu+ mu-) < 3.2 x 10^-9 at 95% confidence level.

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arXiv2012

Measurement of the CP violating phase ϕ_s in Bs->J/ψf0(980)

Measurement of mixing-induced CP violation in Bs decays is of prime importance in probing new physics. So far only the channel Bs->J/ψϕ has been used. Here we report on a measurement using an LHCb data sample of 0.41/fb in the CP odd eigenstate Jψf0(980), where f0(980)->π+ π-. A time dependent fit of the data with the Bs lifetime and the difference in widths of the heavy and light eigenstates constrained to the values obtained from Bs-> J/ψϕ yields a value of the CP violating phase of -0.44 +/- 0.44 +/- 0.02 rad, consistent with the Standard Model expectation.

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arXiv2011

Measurement of mixing and CP violation parameters in two-body charm decays

A study of mixing and indirect CP violation in D0 mesons through the determination of the parameters y_CP and A_Γ is presented. The parameter y_CP is the deviation from unity of the ratio of effective lifetimes measured in D0 decays to the CP eigenstate K+K- with respect to decays to the Cabibbo favoured mode K-π+. The result measured using data collected by LHCb in 2010, corresponding to an integrated luminosity of 29 pb^-1, is y_CP = (5.5+/-6.3_{stat}+/-4.1_{syst}) x 10^-3. The parameter A_Γ is the asymmetry of effective lifetimes measured in decays of D0 and anti-D0 mesons to K+K-. The result is A_Γ = (-5.9+/-5.9_{stat}+/-2.1_{syst}) x 10^-3. A data-driven technique is used to correct for lifetime-biasing effects.

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arXiv2011

Measurement of charged particle multiplicities in $pp$ collisions at ${\sqrt{s} =7}$TeV in the forward region

The charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of ${\sqrt{s} =7}$TeV in different intervals of pseudorapidity $η$. The charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the $η$ ranges $-2.5<η<-2.0$ and $2.0<η<4.5$. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of $η$. In general, the models underestimate the charged particle production.

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arXiv2008

Study of in-medium $ω$ meson properties in Ap, pA and AA collisions

We propose to investigate the in-medium properties of vector $ω$ mesons at the normal nuclear density in Ap(pA) collisions and at higher density in AA collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap kinematics will permit us to study the $ω$ meson production in a wide momentum interval included the not yet explored range of small meson momenta relative to the projectile nuclei where the mass modification effect in nuclear matter is expected to be the strongest. Momentum dependence of the in-medium $ω$ meson width will be studied in the traditional pA kinematics. We intend to use the electromagnetic calorimeter for reconstruction of the $ω$ meson invariant mass by detecting photons from the $ω\to π^{0}γ\to 3γ$ decay. The model calculations and simulations with RQMD generator show feasibility of the proposed experiment. Available now intensity of the ion beams provides a possibility to collect large statistics and make decisive conclusion about the $ω$ meson properties at density of normal nuclei. At the second stage of the investigation the $ω$ meson properties will be studied in AA collisions at higher density. Interpretation of these measurements will be based on the results obtained in Ap(pA) interactions. Further investigation of the in-medium properties of light unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where higher ion energies will be accessible in near future.

nucl-ex↗

arXiv2005

Cosmogenic activation of Germanium and its reduction for low background experiments

Production of $^{60}$Co and $^{68}$Ge from stable isotopes of Germanium by nuclear active component of cosmic rays is a principal background source for a new generation of $^{76}$Ge double beta decay experiments like GERDA and Majorana. The biggest amount of cosmogenic activity is expected to be produced during transportation of either enriched material or already grown crystal. In this letter properties and feasibility of a movable iron shield are discussed. Activation reduction factor of about 10 is predicted by simulations with SHIELD code for a simple cylindrical configuration. It is sufficient for GERDA Phase II background requirements. Possibility of further increase of reduction factor and physical limitations are considered. Importance of activation reduction during Germanium purification and detector manufacturing is emphasized.

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arXiv1997

Scintillation proportional Xe counter with WLS fiber readout for low-energy X-rays

A gas Xe based scintillation proportional counter with cylindrical geometry and wavelength shifting (WLS) fiber readout for X-rays of energy 0.5 - 100 keV is proposed. With such a design large sizes and sensitive area of the counter with a fairly well uniformity is possible. The counter could be used for "dark matter" search and neutrino magnetic moment measurement and for detection of small amounts or traces of radioactive elements in substances or environment.

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