arXiv subjects

E. A. Kravchenko

Publications and source records attributed to E. A. Kravchenko.

At least 37 records · Page 2Linked to original sources

arXiv2018

Measurement of $Γ_{ee}(J/ψ)$ with KEDR detector

The product of the electronic width of the $J/ψ$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $Γ_{ee}(J/ψ) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_\text{hadrons}(J/ψ) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV}, $ $Γ_{ee}(J/ψ) \cdot \mathcal{B}_{ee}(J/ψ) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/ψ$ meson: $Γ= 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.

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arXiv2016

Measurement of $R$ between 1.84 and 3.05 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have determined the values of $R$ at thirteen points of the center-of-mass energy between 1.84 and 3.05 GeV. The achieved accuracy is about or better than $3.9\%$ at most of the energy points with a systematic uncertainty less than $2.4\%$.

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arXiv2016

Measurement of the $\mathbf{e^+e^-\to K^+K^-}$ cross section in the energy range $\mathbf{\sqrt{s}=1.05-2.0}$ GeV

The $e^+e^-\to K^+K^-$ cross section is measured in the center-of-mass energy range $1.05-2.00$ GeV at the SND detector. The measurement is based on data with an integrated luminosity of 35 pb$^{-1}$ collected at the VEPP-2000 $e^+e^-$-collider. The obtained results are consistent with the previous most accurate data obtained in the BABAR experiment and have a comparable accuracy.

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arXiv2015

Measurement of $R_{\text{uds}}$ and $R$ between 3.12 and 3.72 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have measured the values of $R_{\text{uds}}$ and $R$ at seven points of the center-of-mass energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or better than $3.3\%$ at most of energy points with a systematic uncertainty of about $2.1\%$. At the moment it is the most accurate measurement of $R(s)$ in this energy range.

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arXiv2014

Measurement of $J/ψ\toγη_{\rm c}$ decay rate and $η_{\rm c}$ parameters at KEDR

Using the inclusive photon spectrum based on a data sample collected at the $J/ψ$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we measured the rate of the radiative decay $J/ψ\toγη_{\rm c}$ as well as $η_{\rm c}$ mass and width. Taking into account an asymmetric photon lineshape we obtained $Γ^0_{γη_{\rm c}}=2.98\pm0.18 \phantom{|}^{+0.15}_{-0.33}$ keV, $M_{η_{\rm c}} = 2983.5 \pm 1.4 \phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $Γ_{η_{\rm c}} = 27.2 \pm 3.1 \phantom{|}^{+5.4}_{-2.6}$ MeV.

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arXiv2014

Evidence for the decay B0 --> omega omega and search for B0 --> omega phi

We describe searches for B meson decays to the charmless vector-vector final states omega omega and omega phi with 471 x 10^6 B Bbar pairs produced in e+ e- annihilation at sqrt(s) = 10.58 GeV using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction B(B0 --> omega omega) = (1.2 +- 0.3 +0.3-0.2) x 10^-6, where the first uncertainty is statistical and the second is systematic, corresponding to a significance of 4.4 standard deviations. We also determine the upper limit B(B0 --> omega phi) < 0.7 x 10^-6 at 90% confidence level. These measurements provide the first evidence for the decay B0 --> omega omega, and an improvement of the upper limit for the decay B0 --> omega phi.

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arXiv2014

Measurement of the ratio of the leptonic widths $Γ_{ee}/Γ_{μμ}$ for the $J/ψ$ meson

The ratio of the electron and muon widths of the $J/ψ$ meson has been measured using direct $J/ψ$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $Γ_{ee}(J/ψ)/Γ_{μμ}(J/ψ)=1.0022\pm0.0044\pm0.0048\ (0.65\%)$ is in good agreement with the lepton universality. The experience collected during this analysis will be used for a $J/ψ$ lepton width determination with up to 1% accuracy.

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arXiv2013

Parameters of charmonium states from KEDR

We report results of experiments performed with the KEDR detector at the VEPP-4M $e^+e^-$ collider. They include final results for the mass and other parameters of the $J/ψ$, $ψ(2S)$ and $ψ(3770)$ and $J/ψ\toγη_c$ branching fraction determination.

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arXiv2013

SuperB Technical Design Report

In this Technical Design Report (TDR) we describe the SuperB detector that was to be installed on the SuperB e+e- high luminosity collider. The SuperB asymmetric collider, which was to be constructed on the Tor Vergata campus near the INFN Frascati National Laboratory, was designed to operate both at the Upsilon(4S) center-of-mass energy with a luminosity of 10^{36} cm^{-2}s^{-1} and at the tau/charm production threshold with a luminosity of 10^{35} cm^{-2}s^{-1}. This high luminosity, producing a data sample about a factor 100 larger than present B Factories, would allow investigation of new physics effects in rare decays, CP Violation and Lepton Flavour Violation. This document details the detector design presented in the Conceptual Design Report (CDR) in 2007. The R&D and engineering studies performed to arrive at the full detector design are described, and an updated cost estimate is presented. A combination of a more realistic cost estimates and the unavailability of funds due of the global economic climate led to a formal cancelation of the project on Nov 27, 2012.

physics.ins-det↗

arXiv2013

Study of the decay $\bar{B}^{0}\rightarrowΛ_{c}^{+}\bar{p}π^{+}π^{-}$ and its intermediate states

We study the decay $\bar{B}^{0}\rightarrowΛ_{c}^{+}\bar{p}π^{+}π^{-}$, reconstructing the Λ_{c}^{+} baryon in the $p K^{-}π^{+}$ mode, using a data sample of $467\times 10^{6}$ $B\bar{B}$ pairs collected with the BaBar detector at the PEP-2 storage rings at SLAC. We measure branching fractions for decays with intermediate $Σ_{c}$ baryons to be ${\cal B}[\bar{B}^{0}\rightarrowΣ_{c}(2455)^{++}\bar{p}π^{-}]=(21.3 \pm 1.0 \pm 1.0 \pm 5.5) \times 10^{-5}$, ${\cal B}[\bar{B}^{0}\rightarrowΣ_{c}(2520)^{++}\bar{p}π^{-}]=(11.5\pm 1.0 \pm 0.5 \pm 3.0)\times 10^{-5}$, ${\cal B}[\bar{B}^{0}\rightarrowΣ_{c}(2455)^{0}\bar{p}π^{+}]=(9.1 \pm 0.7 \pm 0.4 \pm 2.4)\times10^{-5}$, and ${\cal B}[\bar{B}^{0}\rightarrowΣ_{c}(2520)^{0}\bar{p}π^{+}]= (2.2 \pm 0.7 \pm 0.1\pm 0.6) \times 10^{-5}$, where the uncertainties are statistical, systematic, and due to the uncertainty on the $Λ_{c}^{+}\rightarrow\proton\Kmπ^{+}$ branching fraction, respectively. For decays without $Σ_{c}(2455)$ or $Σ_{c}(2520)$ resonances, we measure ${\cal B}[\bar{B}^{0}\rightarrowΛ_{c}^{+}\bar{p}π^{+}π^{-}]_{\mathrm{non-Σ_{c}}}=(79 \pm 4 \pm 4 \pm 20)\times10^{-5}$. The total branching fraction is determined to be ${\cal B}[\bar{B}^{0}\rightarrowΛ_{c}^{+}\bar{p}π^{+}π^{-}]_{\mathrm{total}}=(123 \pm 5 \pm 7 \pm 32)\times10^{-5}$. We examine multibody mass combinations in the resonant three-particle $Σ_{c}\bar{p}π$ final states and in the four-particle $Λ_{c}^{+}\bar{p}π^{+}π^{-}$ final state, and observe different characteristics for the $\bar{p}π$ combination in neutral versus doubly-charged $Σ_{c}$ decays.

hep-ex↗

arXiv2013

Search for direct CP-violation in singly-Cabibbo suppressed D+- --> K+ K- pi+- decays

We report on a search for direct CP asymmetry in the singly Cabibbo-suppressed decay D+- --> K+ K- pi+- using a data sample of 476 fb-1 accumulated with the BaBar detector running at and just below the Y(4S) resonance. The CP-violating decay rate asymmetry A_CP is determined to be (0.35 +- 0.30 +- 0.15)%. Model-dependent and model-independent Dalitz plot analysis techniques are used to search for CP-violating asymmetries in the various intermediate states.

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arXiv2013

Observation of Time Reversal Violation in the B0 Meson System

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time reversal violation. The decays of entangled neutral B mesons into definite flavor states ($B^0$ or $\bar{B}^0$), and $J/ψK_S^0$ or $c\bar{c} K_S^0$ final states (referred to as $B_+$ or $B_-$), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, $\bar{B}^0 \rightarrow B_-$ and $B_- \rightarrow \bar{B}^0$, as a function of the time difference between the two B decays. Using 468 million $B\bar{B}$ pairs produced in $Υ(4S)$ decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding $ΔS_T^+ = -1.37 \pm 0.14 (stat.) \pm 0.06 (syst.)$ and $ΔS_T^- = 1.17 \pm 0.18 (stat.) \pm 0.11 (syst.)$. These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

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arXiv2012

Branching fraction and form-factor shape measurements of exclusive charmless semileptonic B decays, and determination of |V_{ub}|

We report the results of a study of the exclusive charmless semileptonic decays, B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu, B^+ --> eta l^+ nu and B^+ --> eta^' l^+ nu, (l = e or mu) undertaken with approximately 462x10^6 B\bar{B} pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q^2, the square of the momentum transferred to the lepton-neutrino pair, for B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu and B^+ --> eta l^+ nu. From these distributions, we extract the form-factor shapes f_+(q^2) and the total branching fractions BF(B^0 --> pi^- l^+ nu) = (1.45 +/- 0.04_{stat} +/- 0.06_{syst})x10^-4 (combined pi^- and pi^0 decay channels assuming isospin symmetry), BF(B^+ --> omega l^+ nu) = (1.19 +/- 0.16_{stat} +/- 0.09_{syst})x10^-4 and BF(B^+ --> eta l^+ nu) = (0.38 +/- 0.05_{stat} +/- 0.05_{syst})x10^-4. We also measure BF(B^+ --> eta^' l^+ nu) = (0.24 +/- 0.08_{stat} +/- 0.03_{syst})x10^-4. We obtain values for the magnitude of the CKM matrix element V_{ub} by direct comparison with three different QCD calculations in restricted q^2 ranges of B --> pi l^+ nu decays. From a simultaneous fit to the experimental data over the full q^2 range and the FNAL/MILC lattice QCD predictions, we obtain |V_{ub}| = (3.25 +/- 0.31)x10^-3, where the error is the combined experimental and theoretical uncertainty.

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arXiv2012

Initial-State Radiation Measurement of the e+e- -> pi+pi-pi+pi- Cross Section

We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.

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arXiv2012

Measurement of ψ(3770) parameters

We report the final results of a study of the ψ(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron-positron collider. The data analysis takes into account the interference between the resonant and nonresonant $D\bar{D}$ production, where the latter is related to the nonresonant part of the energy-dependent form factor $F_D$. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant $F_D^{\NR}(s)$. Our results for the mass and total width of ψ(3770) are M = 3779.2 ^{+1.8}_{-1.7} ^{+0.5}_{-0.7} ^{+0.3}_{-0.3} MeV, Γ=24.9 ^{+4.6}_{-4.0} ^{+0.5}_{-0.6} ^{+0.2}_{-0.9} MeV, where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: (1) Γ_{ee} = 154 ^{+79}_{-58} ^{+17}_{-9} ^{+13}_{-25} eV, (2) Γ_{ee} = 414 ^{+72}_{-80} ^{+24}_{-26} ^{+90}_{-10} eV. Our statistics are insufficient to prefer one solution to another. The solution (2) mitigates the problem of non-$D\bar{D}$ decays but is disfavored by potential models. It is shown that taking into account the resonance--continuum interference in the near-threshold region affects resonance parameters, thus the results presented can not be directly compared with the corresponding PDG values obtained ignoring this effect.

hep-ex↗

arXiv2012

A Measurement of the Semileptonic Branching Fraction of the B_s Meson

We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon(4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2.5/-2.0)(stat)(+1.1/-1.9)(syst)%, where l indicates the average of e and mu.

hep-ex↗

arXiv2011

Study of radiative bottomonium transitions using converted photons

We use 111+/-1 million Upsilon(3S) and 89+/-1 million Upsilon(2S) events recorded by the BaBar detector at the PEP-II B-factory at SLAC to perform a study of radiative transitions between bottomonium states using photons that have been converted to e+e- pairs by the detector material. We observe Upsilon(3S) -> gamma chi_b0,2(1P) decay, make precise measurements of the branching fractions for chi_b1,2(1P,2P) -> gamma Upsilon(1S) and chi_b1,2(2P) -> gamma Upsilon(2S) decays, and search for radiative decay to the eta_b(1S) and eta_b(2S) states.

hep-ex↗

arXiv2011

Measurement of main parameters of the ψ(2S) resonance

A high-precision determination of the main parameters of the ψ(2S) resonance has been performed with the KEDR detector at the VEPP-4M e^{+}e^{-} collider in three scans of the ψ(2S) -- ψ(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the ψ(2S) we obtained the mass value M = 3686.114 +- 0.007 +- 0.011 ^{+0.002}_{-0.012} MeV and the product of the electron partial width by the branching fraction into hadrons Γ_{ee}*B_{h} = 2.233 +- 0.015 +- 0.037 +- 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e^{+}e^{-} annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the ψ(2S): Γ_{ee} =2.282 +- 0.015 +- 0.038 +- 0.021 keV, Γ= 296 +- 2 +- 8 +- 3 keV. These results are consistent with and more than two times more precise than any of the previous experiments.

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