-
BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli,
Y. Ban, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482
pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt
s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the
BEPCII storage ring, we search for \psi(3770) and \psi(4040) decay to baryonic
final states, including \Lambda\bar\Lambda\pi^+\pi^-, \Lambda \bar\Lambda\pi^0,
\Lambda\bar\Lambda\eta, \Sigma^+ \bar\Sigma^-, \Sigma^0 \bar\Sigma^0,
\Xi^-\bar\Xi^+ and \Xi^0\bar\Xi^0 decays. None are observed, and upper limits
are set at the 90% confidence level.
05/2013;
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Using a sample of $1.06 \times 10^{8}$ $\psi(2S)$ events collected with the
BESIII detector at BEPCII, the decay $\psi(2S) \to p \bar{p}\eta$ is studied. A
partial wave analysis determines that the intermediate state N(1535) with a
mass of $1524\pm5^{+10}_{-4}$ MeV/$c^2$ and a width of $130^{+27+57}_{-24-10}$
MeV/$c^2$ is dominant in the decay; the product branching fraction is
determined to be $B(\psi(2S) \to N(1535)\bar{p})\times B(N(1535)\to p\eta)+c.c.
= (5.2\pm0.3^{+3.2}_{-1.2})\times 10^{-5}$. Furthermore, the branching fraction
of $\psi(2S) \to \eta p \bar{p}$ is measured to be $(6.4\pm0.2\pm0.6)\times
10^{-5}$.
04/2013;
-
BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
X. C. Ai,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: We study the process e+e- to pi+pi-J/psi at a center-of-mass energy of 4.260
GeV using a 525 pb^{-1} data sample collected with the BESIII detector
operating at the Beijing Electron Positron Collider. The Born cross section is
measured to be (62.9\pm 1.9\pm 3.7) pb, consistent with the production of the
Y(4260). We observe a structure at around 3.9 GeV/c^2 in the \pi^\pm J/psi mass
spectrum, which we refer to as the Z_c(3900). If interpreted as a new particle,
it is unusual in that it carries an electric charge and couples to charmonium.
A fit to the \pi^\pm J/psi invariant mass spectrum, neglecting interference,
results in a mass of (3899.0\pm 3.6\pm 4.9) MeV/c^2 and a width of (46\pm 10\pm
20) MeV. Its production ratio is measured to be R=\frac{\sigma(e+e- to \pi^\pm
Z_c(3900)^\mp to pi+pi-J/psi))} {\sigma(e+e- to pi+pi-J/psi)}=(21.5\pm 3.3\pm
7.5)%. In all measurements the first errors are statistical and the second are
systematic.
03/2013;
-
The BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli,
Y. Ban, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: The decay $J/\psi \rightarrow \omega p \bar{p}$ has been studied, using
$225.3\times 10^{6}$ $J/\psi$ events accumulated at BESIII. No significant
enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as
$X(p\bar{p})$) is observed. The upper limit of the branching fraction
$\mathcal{B}(J/\psi \rightarrow \omega X(p\bar{p}) \rightarrow \omega p
\bar{p})$ is determined to be $4.2\times10^{-6}$ at the 95% confidence level.
The branching fraction of $J/\psi \rightarrow \omega p \bar{p}$ is measured to
be $\mathcal{B}(J/\psi \rightarrow \omega p \bar{p}) =(9.0 \pm 0.2\
(\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.
03/2013;
-
M Ablikim,
M N Achasov,
D J Ambrose,
F F An,
Q An,
Z H An,
J Z Bai,
Y Ban,
J Becker,
N Berger, [......],
S H Zhu,
X L Zhu,
X W Zhu,
Y M Zhu,
Y S Zhu,
Z A Zhu,
J Zhuang,
B S Zou,
J H Zou,
J X Zuo
[show abstract]
[hide abstract]
ABSTRACT: Based on 106×10^{6}ψ(3686) events collected with the BESIII detector at the BEPCII facility, a partial wave analysis of ψ(3686)→pp[over ¯]π^{0} is performed. The branching fraction of this channel has been determined to be B(ψ(3686)→pp[over ¯]π^{0})=(1.65±0.03±0.15)×10^{-4}. In this decay, 7 N^{*} intermediate resonances are observed. Among these, two new resonances, N(2300) and N(2570) are significant, one 1/2^{+} resonance with a mass of 2300_{-30-0}^{+40+109} MeV/c^{2} and width of 340_{-30-58}^{+30+110} MeV/c^{2}, and one 5/2^{-} resonance with a mass of 2570_{-10-10}^{+19+34} MeV/c^{2} and width of 250_{-24-21}^{+14+69} MeV/c^{2}. For the remaining 5 N^{*} intermediate resonances [N(1440), N(1520), N(1535), N(1650) and N(1720)], the analysis yields mass and width values that are consistent with those from established resonances.
Physical Review Letters 01/2013; 110(2):022001. · 7.37 Impact Factor
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 nb^{-1} of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt[s_{NN}]=2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.
Physical Review Letters 01/2013; 110(2):022301. · 7.37 Impact Factor
-
The BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: We search for the M1 radiative transition \psi(3686) \to \gamma\eta_{c}(2S)
by reconstructing the exclusive \eta_{c}(2S) \to
K_{S}^{0}K^{\pm}\pi^{\mp}\pi^{+}\pi^{-} decay using 1.06 \times 10^8 \psi(3686)
events collected with the BESIII detector. The signal is observed with a
statistical significance of greater than 4 standard deviations. The measured
mass of the \eta_{c}(2S) is 3646.9 \pm 1.6(stat) \pm 3.6(syst) MeV/c^2, and the
width is 9.9 \pm 4.8(stat) \pm 2.9(syst) MeV/c^2. The product branching
fraction is measured to be B(\psi(3686) \to \gamma\eta_{c}(2S)) \times
B(\eta_{c}(2S) \to K_{S}^{0}K^{\pm}\pi^{\mp}\pi^{+}\pi^{-}) = (7.03 \pm
2.10(stat) \pm 0.70(syst)) \times 10^{-6}. This measurement complements a
previous BESIII measurement of \psi(3686) \to \gamma\eta_{c}(2S) with
\eta_{c}(2S) \to K_{S}^{0} K^{\pm}\pi^{\mp} and K^{+}K^{-}\pi^{0}.
01/2013;
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb^{-1} are used. Good agreement is observed between the data and the standard model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates.
Physical Review Letters 01/2013; 110(1):011802. · 7.37 Impact Factor
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Based on a sample of $2.25\times 10^{8}$ $J/\psi$ events collected with the
BESIII detector at BEPCII, a full partial wave analysis on
$J/\psi\to\gamma\eta\eta$ was performed using the relativistic covariant tensor
amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$
components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2'(1525)$,
$f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions
are also presented.
12/2012;
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb^{-1} of pp collisions recorded at a center-of-mass energy of sqrt[s]=7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1.6/ϵ fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where ϵ is the monopole reconstruction efficiency. The efficiency ϵ is high and uniform in the fiducial region given by pseudorapidity |η|<1.37 and transverse kinetic energy 600-700<E^{kin}sinθ<1400 GeV. The minimum value of 700 GeV is for monopoles of mass 200 GeV, whereas the minimum value of 600 GeV is applicable for higher mass monopoles. Therefore, the upper limit on the production cross section at 95% confidence level is 2 fb in this fiducial region. Assuming the kinematic distributions from Drell-Yan pair production of spin-1/2 Dirac magnetic monopoles, the efficiency is in the range 1%-10%, leading to an upper limit on the cross section at 95% confidence level that varies from 145 fb to 16 fb for monopoles with mass between 200 GeV and 1200 GeV. This limit is weaker than the fiducial limit because most of these monopoles lie outside the fiducial region.
Physical Review Letters 12/2012; 109(26):261803. · 7.37 Impact Factor
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker,
J. V. Bennett, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: A 2.25$\times10^8$ $\jpsi$ event sample accumulated with the BESIII detector
is used to study the doubly OZI suppressed decay modes $\jpsi\to\gamma\of$,
$\omega\to\ppp$, $\phi\to\kk$. A strong deviation ($>$ 30$\sigma$) from
three-body $\jpsi\to\gamma\omega\phi$ phase space is observed near the
$\omega\phi$ mass threshold that is consistent with a previous observation
reported by the BESII experiment. A partial wave analysis with a tensor
covariant amplitude that assumes that the enhancement is due to the presence of
a resonance, the X(1810), is performed, and confirms that the spin-parity of
the X(1810) is $0^{++}$. The mass and width of the X(1810) are determined to be
$M=1795\pm7$(stat)$^{+13}_{-5}$(syst)$\pm$19(mod) MeV/$c^2$ and
$\Gamma=95\pm10$(stat)$^{+21}_{-34}$(syst)$\pm$75(mod) MeV/$c^2$, respectively,
and the product branching fraction is measured to be ${\cal B}(\jpsi\to\gamma
X(1810))\times{\cal
B}(X(1810)\to\of)=(2.00\pm0.08$(stat)$^{+0.45}_{-1.00}$(syst)$\pm$1.30(mod))$\times10^{-4}$.
%where the first error is the statistical error and the second the systematical
error. These results are consistent within errors with those of the BESII
experiment.
11/2012;
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV. The measurement is based on 4.7 fb^{-1} of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.
Physical Review Letters 11/2012; 109(21):211803. · 7.37 Impact Factor
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search for direct pair production of supersymmetric top squarks (t[over ˜]_{1}) is presented, assuming the t[over ˜]_{1} decays into a top quark and the lightest supersymmetric particle, χ[over ˜]_{1}^{0}, and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5_{-3.6}^{+3.7}(4.4_{-1.3}^{+1.7}) events in two signal regions based on ∫Ldt=4.7 fb^{-1} of pp collision data taken at sqrt[s]=7 TeV with the ATLAS detector at the LHC. An exclusion region in the t[over ˜]_{1} versus χ[over ˜]_{1}^{0} mass plane is evaluated: 370<m_{t[over ˜]_{1}}<465 GeV is excluded for m_{χ[over ˜]_{1}^{0}}∼0 GeV while m_{t[over ˜]_{1}}=445 GeV is excluded for m_{χ[over ˜]_{1}^{0}}≤50 GeV.
Physical Review Letters 11/2012; 109(21):211802. · 7.37 Impact Factor
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
R. Baldini Ferroli,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Using a sample of 225.3 million $\jpsi$ events collected with the BESIII
detector at the BEPCII $e^+e^-$ collider in 2009, searches for the decays of
$\eta$ and $\eta^\prime\to\pi^+ e^- \bar{\nu}_e +c.c.$ in $\jpsi \to \phi \eta$
and $\phi\eta^\prime$ are performed. The $\phi$ signals, which are
reconstructed in $K^+K^-$ final states, are used to tag $\eta$ and
$\eta^\prime$ semileptonic decays. No signals are observed for either $\eta$ or
$\eta^\prime$, and upper limits at the 90% confidence level are determined to
be $7.3\times 10^{-4}$ and $5.0\times 10^{-4}$ for the ratios $\frac{{\mathcal
B}(\eta\to \pi^+ e^- \bar{\nu}_e +c.c.)}{{\mathcal B}(\eta \to \pip\pim\piz)}$
and $\frac{{\mathcal B}(\eta^\prime\to \pi^+ e^-\bar{\nu}_e +c.c.)}{{\mathcal
B}(\eta^\prime \to \pip\pim\eta)}$, respectively. These are the first upper
limit values determined for $\eta$ and $\eta^\prime$ semileptonic weak decays.
11/2012;
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker,
J. V. Bennett, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Using 106 $\times 10^{6}$ $\psi^{\prime}$ decays collected with the BESIII
detector at the BEPCII, three decays of $\chi_{cJ}$ ($J=0,1,2$) with baryon
pairs ($\llb$, $\ssb$, $\SSB$) in the final state have been studied. The
branching fractions are measured to be
$\cal{B}$$(\chi_{c0,1,2}\rightarrow\Lambda\bar\Lambda) =(33.3 \pm 2.0 \pm
2.6)\times 10^{-5}$, $(12.2 \pm 1.1 \pm 1.1)\times 10^{-5}$, $(20.8 \pm 1.6 \pm
2.3)\times 10^{-5}$;
$\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{0}\bar\Sigma^{0})$ = $(47.8 \pm 3.4
\pm 3.9)\times 10^{-5}$, $(3.8 \pm 1.0 \pm 0.5)\times 10^{-5}$, $(4.0 \pm 1.1
\pm 0.5) \times 10^{-5}$; and
$\cal{B}$$(\chi_{c0,1,2}\rightarrow\Sigma^{+}\bar\Sigma^{-})$ = $(45.4 \pm 4.2
\pm 3.0)\times 10^{-5}$, $(5.4 \pm 1.5 \pm 0.5)\times 10^{-5}$, $(4.9 \pm 1.9
\pm 0.7)\times 10^{-5}$, where the first error is statistical and the second is
systematic. Upper limits on the branching fractions for the decays of
$\chi_{c1,2}\rightarrow\Sigma^{0}\bar\Sigma^{0}$, $\Sigma^{+}\bar\Sigma^{-}$,
are estimated to be $\cal{B}$$(\chi_{c1}\rightarrow\Sigma^{0}\bar\Sigma^{0}) <
6.2\times 10^{-5}$, $\cal{B}$$(\chi_{c2}\rightarrow\Sigma^{0}\bar\Sigma^{0}) <
6.5\times 10^{-5}$, $\cal{B}$$(\chi_{c1}\rightarrow\Sigma^{+}\bar\Sigma^{-}) <
8.7\times 10^{-5}$ and $\cal{B}$$(\chi_{c2}\rightarrow\Sigma^{+}\bar\Sigma^{-})
< 8.8\times 10^{-5}$ at the 90% confidence level.
11/2012;
-
M Ablikim,
M N Achasov,
D J Ambrose,
F F An,
Q An,
Z H An,
J Z Bai,
R B Ferroli,
Y Ban,
J Becker, [......],
S H Zhu,
X L Zhu,
X W Zhu,
Y M Zhu,
Y S Zhu,
Z A Zhu,
J Zhuang,
B S Zou,
J H Zou,
J X Zuo
[show abstract]
[hide abstract]
ABSTRACT: The two-photon transition ψ(3686)→γγJ/ψ is studied in a sample of 1.06×10^{8} ψ(3686) decays collected by the BESIII detector. The branching fraction is measured to be (3.1±0.6(stat)_{-1.0}^{+0.8}(syst))×10^{-4} using J/ψ→e^{+}e^{-} and J/ψ→μ^{+}μ^{-} decays, and its upper limit is estimated to be 4.5×10^{-4} at the 90% confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the ψ(3686) decay plane and the J/ψ polarization in this decay are also studied. In addition, the product branching fractions of sequential E1 transitions ψ(3686)→γχ_{cJ} and χ_{cJ}→γJ/ψ(J=0,1,2) are reported.
Physical Review Letters 10/2012; 109(17):172002. · 7.37 Impact Factor
-
The BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Using a data sample of $2.25\times10^{8}$ $J/\psi$ events collected with the
BESIII detector, we present the first observation of the decays of $\eta_{c}$
mesons to $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$. The
branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm
syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm
stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $\eta_{c} \to
\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$, respectively. These
branching fractions provide important information on the helicity selection
rule in charmonium-decay processes.
10/2012;
-
The BESIII Collaboration,
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: The process $\psi(3686) \to \pi^0 h_c, h_c \to \gamma \eta_c$ has been
studied with a data sample of $106 \pm 4$ million $\psi(3686)$ events collected
with the BESIII detector at the BEPCII storage ring. The mass and width of the
$P$-wave charmonium spin-singlet state $h_c(^1P_1)$ are determined by
simultaneously fitting distributions of the $\pi^0$ recoil mass for 16
exclusive $\eta_c$ decay modes. The results, $M(\hc) = 3525.31 \pm 0.11 {\rm
(stat.)} \pm 0.14 {\rm (syst.)}$\,MeV/$c^2$ and $\Gamma(\hc) = 0.70 \pm 0.28
\pm 0.22$\,MeV, are consistent with and more precise than previous
measurements. We also determine the branching ratios for the 16 exclusive
$\eta_c$ decay modes, five of which have not been measured previously. New
measurements of the $\eta_c$ line-shape parameters in the $E1$ transition
$h_c\to\gamma\eta_c$ are made by selecting candidates in the $h_c$ signal
sample and simultaneously fitting the hadronic mass spectra for the 16 $\eta_c$
decay channels. The resulting $\eta_c$ mass and width values are $M(\eta_c) =
2984.49 \pm 1.16 \pm 0.52$\,MeV/$c^2$ and $\Gamma(\eta_c) = 36.4 \pm 3.2 \pm
1.7$\,MeV.
09/2012;
-
M. Ablikim,
M. N. Achasov,
D. J. Ambrose,
F. F. An,
Q. An,
Z. H. An,
J. Z. Bai,
Y. Ban,
J. Becker,
J. V. Bennett, [......],
S. H. Zhu,
X. L. Zhu,
X. W. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Decays of the χcJ states (J=0, 1, 2) to ΛΛ̅ π+π-, including processes with intermediate Σ(1385), are studied through the E1 transition ψ′→γχcJ using 106×106 ψ′ events collected with the BESIII detector at BEPCII. This is the first observation of χcJ decays to the final state ΛΛ̅ π+π-. The branching ratio of the intermediate process χcJ→Σ(1385)±Σ̅ (1385)∓ is also measured for the first time, and the results agree with the theoretical predictions based on the color-octet effect.
Phys. Rev. D. 09/2012; 86(5).
-
M. Ablikim,
M. N. Achasov,
O. Albayrak,
D. J. Ambrose,
F. F. An,
Q. An,
J. Z. Bai,
Y. Ban,
J. Becker,
J. V. Bennett, [......],
K. J. Zhu,
S. H. Zhu,
X. L. Zhu,
Y. C. Zhu,
Y. M. Zhu,
Y. S. Zhu,
Z. A. Zhu,
J. Zhuang,
B. S. Zou,
J. H. Zou
[show abstract]
[hide abstract]
ABSTRACT: Using a sample of $(225.3\pm 2.8)\times 10^{6}$ $J/\psi$ decays collected
with the BESIII detector at BEPCII, searches for invisible decays of $\eta$ and
$\eta^\prime$ in $J/\psi\to\phi\eta$ and $\phi\eta^\prime$ are performed.
Decays of $\phi \to K^{+}K^{-}$ are used to tag the $\eta$ and $\eta^\prime$
decays. No signals above background are found for the invisible decays, and
upper limits at the 90% confidence level are determined to be
$2.58\times10^{-4}$ for the ratio
$\frac{\mathcal{B}(\eta\to\rm{invisible})}{\mathcal{B}(\eta\to\gamma\gamma)}$
and $2.39\times10^{-2}$ for
$\frac{\mathcal{B}(\eta^\prime\to\rm{invisible})}{\mathcal{B}(\eta^\prime
\to\gamma\gamma)}$.
09/2012;
