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G. Chelkov

Publications and source records attributed to G. Chelkov.

At least 685 records · Page 38Linked to original sources
arXiv2012

Experimental study of psi' decays to K+K- pi^0 and K+K- eta

Using $(106\pm4)\times 10^6$ $\psip$ events accumulated with the BESIII detector at the BEPCII $e^+e^-$ collider, we present measurements of the branching fractions for psi' decays to $K^{+}K^{-}π^{0}$ and $K^{+}K^{-}η$. In these final states, the decay $ψ'\to K_2^{*}(1430)^+K^-+c.c.$ is observed for the first time, and its branching fraction is measured to be $(7.12\pm{0.62}{\rm (stat.)}^{+1.13}_{-0.61}{\rm (syst.)})\times 10^{-5}$, which indicates a violation of the helicity selection rule in $\psip$ decays. The branching fractions of $ψ'\to K^*(892)^+K^-+c.c., ϕη, ϕπ^0$ are also measured. The measurements are used to test the QCD predictions on charmonium decays.

hep-ex↗
arXiv2012

Observation of $e^{+}e^{-} \to ηJ/ψ$ at center-of-mass energy $sqrt{s}=4.009$ GeV

Using a 478 pb$^{-1}$ data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $\sqrt{s}=4.009$ GeV, the production of $e^{+}e^{-}\to ηJψ$ is observed for the first time with a statistical significance of greater than $10σ$. The Born cross section is measured to be $(32.1\pm 2.8 \pm 1.3)$ pb, where the first error is statistical and the second systematic. Assuming the $ηJψ$ signal is from a hadronic transition of the $ψ(4040)$, the fractional transition rate is determined to be ${\cal B}(ψ(4040)\to ηJψ)=(5.2\pm 0.5\pm 0.2\pm 0.5)\times 10^{-3}$, where the first, second, and third errors are statistical, systematic, and the uncertainty from the $ψ(4040)$ resonant parameters, respectively. The production of $e^{+}e^{-} \to π^0 Jψ$ is searched for, but no significant signal is observed, and ${\cal B}(ψ(4040)\to π^0 Jψ) < 2.8 \times 10^{-4}$ is obtained at the 90% confidence level.

hep-ex↗
arXiv2012

Measurement of $χ_{cJ}$ decaying into $p\bar{n}π^{-}$ and $p\bar{n}π^{-}π^{0}$

Using a data sample of $1.06 \times 10^{8}$ $\psip$ events collected with the BESIII detector in 2009, the branching fractions of $χ_{cJ}\to p\bar{n}π^{-}$ and $χ_{cJ}\to p\bar{n}π^{-}π^{0}$ ($J$=0,1,2) are measured{Throughout the text, inclusion of charge conjugate modes is implied if not stated otherwise.}. The results for $χ_{c0}\to p\bar{n}π^{-}$ and $χ_{c2}\to p\bar{n}π^{-}$ are consistent with, but much more precise than those of previous measurements. The decays of $χ_{c1}\to p\bar{n}π^{-}$ and $χ_{cJ}\to p\bar{n}π^{-}π^{0}$ are observed for the first time.

hep-ex↗
arXiv2012

Observation of chi_{cJ} Decays to ΛΛbarπ^{+}π^{-}

Decays of the chi_{cJ} states (J=0,\ 1,\ 2) to ΛΛbar\ pi^{+} π^{-}, including processes with intermediate Σ(1385), are studied through the E1 transition psi'-->γchi_{cJ} using 106 million psi' events collected with the BESIII detector at BEPCII. This is the first observation of chi_{cJ} decays to the final state ΛΛbar π^{+}π^{-}. The branching ratio of the intermediate process chi_{cJ}-->Σ(1385)^{+/-} \barΣ(1385)^{-/+} is also measured for the first time, and the results agree with the theoretical predictions based on the color-octet effect.

hep-ex↗
arXiv2012

Search for hadronic transition $χ_{cJ}\toη_{c}π^{+}π^{-}$ and observation of $χ_{cJ}\to K\bar{K}πππ$

Hadronic transitions of $χ_{cJ}\to η_{c}π^{+}π^{-}$ (J=0, 1, 2) are searched for using a sample of $1.06\times 10^{8}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The $\etac$ is reconstructed with $K_{S}^{0}K^{+}π^{-}+c.c.$ and $K^{+}K^{-}π^{0}$ final states. No signals are observed in any of the three $χ_{cJ}$ states in either $\etac$ decay mode. At the 90% confidence level, the upper limits are determined to be $\BR(χ_{c0}\to η_{c}π^{+}π^{-})<0.07%$, $\BR(χ_{c1}\to η_{c}π^{+}π^{-})<0.32%$, and $\BR(χ_{c2}\to η_{c}π^{+}π^{-})<0.54%$. The upper limit of $\BR(χ_{c1}\to η_{c}π^{+}π^{-}$ is lower than the existing theoretical prediction by almost an order of magnitude. The branching fractions of $χ_{cJ}\to K_{S}^{0}K^{+}π^{-}π^{+}π^{-}+c.c.$, $K^{+}K^{-}π^{+}π^{-}π^{0}$, $ωK^{+}K^{-}$ and $ϕπ^{+}π^{-}π^{0}$ (J=0, 1, 2) are measured for the first time.

hep-ex↗
arXiv2012

First observation of the isospin violating decay $J/ψ\rightarrow Λ\barΣ^{0}+c.c.$

Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/ψ$ events collected with the BESIII detector, we present results of a study of $J/ψ\rightarrow γΛ\barΛ$ and report the first observation of the isospin violating decay $J/ψ\rightarrowΛ\barΣ^{0}+c.c.$, in which $\barΣ^{0}$ decays to $γ\barΛ$. The measured branching fractions are $\mathcal{B}(J/ψ\rightarrow\barΛΣ^{0}$) = $(1.46\pm0.11\pm0.12) \times10^{-5}$ and $\mathcal{B}(J/ψ\rightarrowΛ\bar{Σ^{0}}$) = $(1.37\pm0.12\pm0.11) \times10^{-5}$. We search for $Λ(1520) \rightarrow γΛ$ decay, and find no evident signal, and an upper limit for the product branching fraction $\mathcal{B}(J/ψ\rightarrowΛ\barΛ(1520)+c.c.)\times \mathcal{B}(Λ(1520)\rightarrowγΛ)<4.1 \times10^{-6}$ is set at the 90% confidence level. We also report the observation of $η_{c}\rightarrowΛ\barΛ$ in $J/ψ\rightarrow γη_{c}$, $η_{c}\rightarrowΛ\barΛ$ and measure the branching fraction $\mathcal{B}(η_{c}\rightarrowΛ\barΛ) =(1.16\pm0.12 (stat)\pm0.19(syst)\pm0.28(PDG))\times10^{-3}$.

hep-ex↗
arXiv2012

Study of $J/ψ\to p\bar{p}$ and $J/ψ\to n\bar{n}$

The decays $J/ψ\to p\bar{p}$ and $J/ψ\to n\bar{n}$ have been investigated with a sample of 225.2 million $J/ψ$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are determined to be $\mathcal{B}(J/ψ\to p\bar{p})=(2.112\pm0.004\pm0.031)\times10^{-3}$ and $\mathcal{B}(J/ψ\to n\bar{n})=(2.07\pm0.01\pm0.17)\times10^{-3}$. Distributions of the angle $θ$ between the proton or anti-neutron and the beam direction are well described by the form $1+α\cos^2θ$, and we find $α=0.595\pm0.012\pm0.015$ for $J/ψ\to p\bar{p}$ and $α=0.50\pm0.04\pm0.21$ for $J/ψ\to n\bar{n}$. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the $J/ψ\to N\bar{N}$ decay.

hep-ex↗
arXiv2012

First observation of the M1 transition $ψ(3686)\to γη_c(2S)$

Using a sample of 106 million ψ(3686) events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the M1 transition between the radially excited charmonium S-wave spin-triplet and the radially excited S-wave spin-singlet states: ψ(3686)\toγη_c(2S). Analyses of the processes ψ(2S)\to γη_c(2S) with η_c(2S)\to \K_S^0 Kπand K^+K^-π^0 gave an η_c(2S) signal with a statistical significance of greater than 10 standard deviations under a wide range of assumptions about the signal and background properties. The data are used to obtain measurements of the η_c(2S) mass (M(η_c(2S))=3637.6\pm 2.9_\mathrm{stat}\pm 1.6_\mathrm{sys} MeV/c^2), width (Γ(η_c(2S))=16.9\pm 6.4_\mathrm{stat}\pm 4.8_\mathrm{sys} MeV), and the product branching fraction (\BR(ψ(3686)\to γη_c(2S))\times \BR(η_c(2S)\to K\bar Kπ) = (1.30\pm 0.20_\mathrm{stat}\pm 0.30_\mathrm{sys})\times 10^{-5}). Combining our result with a BaBar measurement of \BR(η_c(2S)\to K\bar K π), we find the branching fraction of the M1 transition to be \BR(ψ(3686)\toγη_c(2S)) = (6.8\pm 1.1_\mathrm{stat}\pm 4.5_\mathrm{sys})\times 10^{-4}.

hep-ex↗
arXiv2012

Two-photon widths of the $χ_{c0, 2}$ states and helicity analysis for $χ_{c2}\arγγ$}

Based on a data sample of 106 M $ψ^{\prime}$ events collected with the BESIII detector, the decays $ψ^{\prime}\arγχ_{c0, 2}$,$χ_{c0, 2}\arγγ$ are studied to determine the two-photon widths of the $χ_{c0, 2}$ states. The two-photon decay branching fractions are determined to be ${\cal B}(χ_{c0}\arγγ) = (2.24\pm 0.19\pm 0.12\pm 0.08)\times 10^{-4}$ and ${\cal B}(χ_{c2}\arγγ) = (3.21\pm 0.18\pm 0.17\pm 0.13)\times 10^{-4}$. From these, the two-photon widths are determined to be $Γ_{γγ}(χ_{c0}) = (2.33\pm0.20\pm0.13\pm0.17)$ keV, $Γ_{γγ}(χ_{c2}) = (0.63\pm0.04\pm0.04\pm0.04)$ keV, and $\cal R$ $=Γ_{γγ}(χ_{c2})/Γ_{γγ}(χ_{c0})=0.271\pm 0.029\pm 0.013\pm 0.027$, where the uncertainties are statistical, systematic, and those from the PDG ${\cal B}(ψ^{\prime}\arγχ_{c0,2})$ and $Γ(χ_{c0,2})$ errors, respectively. The ratio of the two-photon widths for helicity $λ=0$ and helicity $λ=2$ components in the decay $χ_{c2}\arγγ$ is measured for the first time to be $f_{0/2} =Γ^{λ=0}_{γγ}(χ_{c2})/Γ^{λ=2}_{γγ}(χ_{c2}) = 0.00\pm0.02\pm0.02$.

hep-ex↗
arXiv2012

First observation of $η(1405)$ decays into $f_{0}(980)π^0$

The decays $J/ψ\rightarrow γπ^+π^-π^0$ and $J/ψ\rightarrow γπ^0π^0π^0$ are analyzed using a sample of 225 million $\jpsi$ events collected with the BESIII detector. The decay of $η(1405)\ar f_{0}(980)π^0$ with a large isospin violation is observed for the first time. The width of the $f_{0}(980)$ observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the $η'$ are also measured precisely.

hep-ex↗
arXiv2012

Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.

hep-ex↗
arXiv2011

Revisiting the 'LSND anomaly' II: critique of the data analysis

This paper, together with a preceding paper, questions the so-called 'LSND anomaly': a 3.8 sigma excess of antielectronneutrino interactions over standard backgrounds, observed by the LSND Collaboration in a beam dump experiment with 800 MeV protons. That excess has been interpreted as evidence for the antimuonneutrino to antielectronneutrino oscillation in the \Deltam2 range from 0.2 eV2 to 2 eV2. Such a \Deltam2 range is incompatible with the widely accepted model of oscillations between three light neutrino species and would require the existence of at least one light 'sterile' neutrino. In a preceding paper, it was concluded that the estimates of standard backgrounds must be significantly increased. In this paper, the LSND Collaboration's estimate of the number of antielectronneutrino interactions followed by neutron capture, and of its error, is questioned. The overall conclusion is that the significance of the 'LSND anomaly' is not larger than 2.3 sigma.

hep-ex↗
arXiv2011

Cross-sections of large-angle hadron production in proton-- and pion--nucleus interactions VIII: aluminium nuclei and beam momenta from {\pm}3 GeV/c to {\pm}15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λint thick stationary aluminium target, of proton and pion beams with momentum from \pm3 GeV/c to \pm15 GeV/c. Results are given for secondary particles with production angles between 20 and 125 degrees. Cross-sections on aluminium nuclei are compared with cross-sections on beryllium, carbon, copper, tin, tantalum and lead nuclei.

hep-ex↗
arXiv2011

Revisiting the 'LSND anomaly' I: impact of new data

This paper, together with a subsequent paper, questions the so-called 'LSND anomaly': a 3.8 σ excess of anti-electronneutrino interactions over standard backgrounds, observed by the LSND Collaboration in a beam dump experiment with 800 MeV protons. That excess has been interpreted as evidence for the anti-muonneutrino{\to} anti-electronneutrino oscillation in the Δm2 range from 0.2 eV2 to 2 eV2. Such a Δm2 range is incompatible with the widely accepted model of oscillations between three light neutrino species and would require the existence of at least one light 'sterile' neutrino. In this paper, new data on pion production by protons on nuclei are presented, and four decades old data on pion production by neutrons on nuclei are recalled, that together increase significantly the estimates of standard backgrounds in the LSND experiment, and decrease the significance of the 'LSND anomaly' from 3.8 σ to 2.9 σ. In a subsequent paper, in addition the LSND Collaboration's data analysis will be questioned, rendering a further reduction of the significance of the 'LSND anomaly'.

hep-ex↗
arXiv2011

Cross-sections of large-angle hadron production in proton- and pion-nucleus interactions VII: tin nuclei and beam momenta from \pm3 GeV/c to \pm15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% nuclear interaction length thick stationary tin target, of proton and pion beams with momentum from \pm3 GeV/c to \pm15 GeV/c. Results are given for secondary particles with production angles between 20 and 125 degrees. Cross-sections on tin nuclei are compared with cross-sections on beryllium, carbon, copper, tantalum and lead nuclei.

hep-ex↗
arXiv2010

Cross-sections of large-angle hadron production in proton- and pion-nucleus interactions VI: carbon nuclei and beam momenta from \pm 3 GeV/c to \pm 15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% nuclear interaction length thick stationary carbon target, of proton and pion beams with momentum from \pm 3 GeV/c to \pm 15 GeV/c. Results are given for secondary particles with production angles between 20 and 125 degrees. Cross-sections on carbon nuclei are compared with cross-sections on beryllium, copper, tantalum and lead nuclei.

hep-ex↗
arXiv2009

Why the paper CERN-PH-EP-2009-015 (arXiv:0903.4762) is scientifically unacceptable

The paper CERN-PH-EP-2009-015 (arXiv:0903.4762) by A. Bagulya et al. violates standards of quality of work and scientific ethics on several counts. The paper contains assertions that contradict established detector physics. The paper falls short of proving the correctness of the authors' concepts and results. The paper ignores or quotes misleadingly pertinent published work. The paper ignores the fact that the authors' concepts and results have already been shown wrong in the published literature. The authors seem unaware that cross-section results from the 'HARP Collaboration' that are based on the paper's concepts and algorithms are in gross disagreement with the results of a second analysis of the same data, and with the results of other experiments.

physics.ins-det↗