The KEDR detector Anashin, V. V.; Aulchenko, V. M.; Baldin, E. M. ...
Physics of particles and nuclei,
07/2013, Letnik:
44, Številka:
4
Journal Article
Recenzirano
The KEDR detector is a universal magnetic detector designed for studying the
c
- and
b
-quarks and two-photon physics, and is employed at the VEPP-4M
e
+
e
−
collider. A specific feature of the ...experiment is the measurement of absolute beam energy using two methods: the resonant depolarization and the faster but less precise Compton backscattering of laser photons. This allowed a large series of measurements to be performed, in which the accuracy of determination of such fundamental parameters of particles as mass and total and leptonic widths was improved.
A three-gauge method of measurements (Nucl. Instrum. Methods A 359 (1995) 110) is described and used to study the photodesorption yields and sticking probabilities of a stainless steel test chamber ...coated with approximately 3
μm of TiZrV getter material.
Using the measured sticking probability for hydrogen of 0.007 for the TiZrV coated chamber and the known sticking probabilities of CH
4, CO and CO
2 of 0, 0.5, 0.5, respectively (Vacuum 60 (2001) 57), the photodesorption yields are deduced. After activation, the H
2, CH
4, CO, and CO
2 desorption yields are found to be 1.5×10
−5, 2×10
−7, <1×10
−5 and <2×10
−6 molecules/photon, respectively. No saturation effect is observed even after a large photon dose.
These results are compared to those from stainless steel test chamber measurements performed for the same geometry under identical conditions.
After saturation with CO and during continuous CO injection, the effect of the irradiation is to reduce the pressure, contrary to the normal dynamic behaviour of a conventional vacuum system. This observation is explained in terms of photon induced pumping of the CO by the TiZrV coating.
We present various properties of the production of the X ( 3872 ) and ψ ( 2S ) states based on 10.4 fb-1 collected by the D0 experiment in Tevatron p p ¯ collisions at s=1.96 TeV . For both states, ...we measure the nonprompt fraction fNP of the inclusive production rate due to decays of b -flavored hadrons. We find the fNP values systematically below those obtained at the LHC. The fNP fraction for ψ ( 2S ) increases with transverse momentum, whereas for the X ( 3872 ) it is constant within large uncertainties, in agreement with the LHC results. The ratio of prompt to nonprompt ψ ( 2S ) production, ( 1-fNP ) / fNP , decreases only slightly going from the Tevatron to the LHC, but for the X ( 3872 ) , this ratio decreases by a factor of about 3. We test the soft-pion signature of the X ( 3872 ) modeled as a weakly bound charm-meson pair by studying the production of the X ( 3872 ) as a function of the kinetic energy of the X ( 3872 ) and the pion in the X ( 3872 ) π center-of-mass frame. For a subsample consistent with prompt production, the results are incompatible with a strong enhancement in the production of the X ( 3872 ) at the small kinetic energy of the X ( 3872 ) and the π in the X ( 3872 ) π center-of-mass frame expected for the X+soft -pion production mechanism. For events consistent with being due to decays of b hadrons, there is no significant evidence for the soft-pion effect, but its presence at the level expected for the binding energy of 0.17 MeV and the momentum scale Λ =M ( π ) is not ruled out.
We present a measurement of the top quark mass in pp collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to ...an integrated luminosity of 9.7fb super(?1). The matrix element technique is applied to tt events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of tt decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of m sub()t173.93+ or -1.84GeV.
The purpose of this work is to study the effect of carbon dioxide oil solubility on the aggregation of asphaltene associates and decrease of oil permeability of sandstones. Consideration is given to ...the interaction variants of oil and carbon dioxide in a free volume before being injected into a porous medium and immediately in the porous medium. The influence of oil composition on the aggregation of asphaltene associates is studied. The effect of the dissolved carbon dioxide on associate dispersion in oil is examined through oil filtering in sandstones. If asphaltene aggregation occurs in a porous medium it causes pore plugging leading to reduced permeability, complicates the development of carbon dioxide injection wells and, as a result, prevents from achieving the planned indicators of oil production and oil recovery. It is found that in the case when oil interacts with carbon dioxide in the free volume before being injected into a porous medium, the increase in the volume of filtered oil and the concentration of carbon dioxide dissolved in oil, and decrease in sandstone permeability reduce the relative mobility of oil with the dissolved carbon dioxide. The significant influence of sandstone permeability on the experimental results indicates that the sizes of asphaltene aggregates are comparable to the sizes of small pores. We have not observed complete attenuation of filtration after passing of oil with dissolved carbon dioxide through sandstones. Based on the analysis of changes in oil composition and properties carried out in the laboratory experiments on oil displacement by carbon dioxide rims, it has been determined that aggregation of asphaltene associates takes place under immediate contact of oil and carbon dioxide in a porous medium. The higher the asphaltene content in oil, the lower the formation permeability, whereas tight formations feature a more significant decrease in permeability.
Abstract Using the 1.32 $$\hbox {pb}^{-1}$$ pb - 1 statistics collected at the $$J/\psi $$ J / ψ peak with the KEDR detector at the VEPP-4M $$e^{+}e^{-\, }$$ e + e - collider, we measured the ...branching fractions of $$J/\psi $$ J / ψ meson decays to the final states 2( $$\pi ^{+}\pi ^{-})\pi ^{0}$$ π + π - ) π 0 , $$K^{+}K^{-}\pi ^{+}\pi ^{-}\pi ^{0}$$ K + K - π + π - π 0 , 2( $$\pi ^{+}\pi ^{-})$$ π + π - ) and $$K^{+}K^{-}\pi ^{+}\pi ^{-}$$ K + K - π + π - . The results obtained for the decays $$J/\psi \rightarrow $$ J / ψ → 2( $$\pi ^{+}\pi ^{-})\pi ^{0}$$ π + π - ) π 0 , $$J/\psi \rightarrow K^{+}K^{-}\pi ^{+}\pi ^{-}\pi ^{0}$$ J / ψ → K + K - π + π - π 0 contradict the measurements performed by other groups in the last century, but agree well with recent results of BABAR and BESIII collaborations.
We study the production of the exotic charged charmonium-like state $Z_c^{\pm}(3900)$ in $p \bar p$ collisions through the sequential process $\psi(4260) \rightarrow Z_c^{\pm}(3900) \pi^{\mp}$, ...$Z_c^{\pm}(3900) \rightarrow J/\psi \pi^{\pm}$. Using the subsample of candidates originating from semi-inclusive weak decays of $b$-flavored hadrons, we measure the invariant mass and natural width to be $M=3902.6^{+5.2}_{-5.0}{\rm \thinspace (stat)}^{+3.3}_{-1.4}{\rm \thinspace (syst)}$ MeV and $\Gamma=32 ^{+28}_{-21}{\rm \thinspace (stat)} ^{+26}_{-7}{\rm \thinspace (syst)}$ MeV, respectively. We search for prompt production of the $Z_c^{\pm}(3900)$ through the same sequential process. No significant signal is observed, and we set an upper limit of 0.66 at the 95\% credibility level on the ratio of prompt production to the production via $b$-hadron decays. The study is based on $10.4~\rm{fb^{-1}}$ of $p \overline p $ collision data collected by the D0 experiment at the Fermilab Tevatron collider.
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