Search

Using a low-background sample of 2.6 x 10(5) J/psi -> omega eta(omega -> pi(+) pi(-) pi(0), eta -> gamma gamma) events, about 5 times larger statistics than previous experiments, we present a Dalitz plot analysis of the decay omega -> pi(+) pi(-) pi(0). It is found that the Dalitz plot distribution differs from the pure P-wave phase space with a statistical significance of 18.9 sigma. The parameters from the fit to data are in reasonable agreement with those without the cross-channel effect within the dispersive framework, which indicates that the cross-channel effect in omega -> pi(+) pi(-) pi(0) is not significant.

By analyzing an e(+)e(-) data sample corresponding to an integrated luminosity of 2.93 fb(-1) taken at a centerof- mass energy of 3.773 GeV with the BESIII detector, we measure the branching fractions of the Cabibbofavored hadronic decays D-0 -> K- pi' eta', D-0 -> K-s(0)pi(0)eta', which are determined to be (6.43 +/- 0.15(stat)+/- 0.31(syst)) x 10(-3), (2.52 +/- 0.22(stat) +/- 0.15(syst)) x 10(-3,) and (1.90 +/- 0.17(stat) +/- 0.13(syst)) x 10(-3), respectively. The precision of the branching fraction of D-0 -> K- pi(+) eta' is significantly improved, and the processes D-0 -> K-S(0)pi(0)eta' and D+ -> K-S(0) pi(+)eta' are observed for the first time.

Based on a data sample of (448.1 +/- 2.9) x 10(6)Psi(3686) decays collected with the BESIII experiment, a search for the flavor changing neutral current transition Psi(3686) -> Lambda(+)(c) pe(+) e(-) + c.c. is performed for the first time. No signal candidates are observed and the upper limit on the branching fraction of Psi(3686) -> Lambda(+)(c) pe(+) e(-) is determined to be 1.7 x 10(-6) at the 90% confidence level. The result is consistent with expectations from the standard model, and no evidence for new physics is found.

The process e(+)e(-) -> D*D-+(s)*(s0) (2317)(-) + c.c. is observed for the first time with the data sample of 567 pb(-1) collected with the BESIII detector operating at the BEPCII collider at a center-of-mass energy root s = 4.6 GeV. The statistical significance of the D*(s0) (2317)(+/-) signal is 5.8 sigma and the mass is measured to be (2318.3 +/- 1.2 +/- 1.2) MeV/c(2). The absolute branching fraction B(D*(s0) (2317)(+/-) -> pi D-0(s)+/-) is measured as 1.00(-0.14)(+0.00) (stat)(-0.14)(+0.00) (syst) for the first time. The uncertainties are statistical and systematic, respectively.

Using a sample of 448.1 x 10(6) psi(3686) events collected with the BESIII detector, a search for the isospin violating decay eta(c) -> pi(+) pi(-) pi(0) via psi(3686) -> gamma eta(c) is presented. No signal is observed, and the upper limit on B(psi(3686) -> gamma eta(c)) x B(eta(c) -> pi(+) pi(-) pi(0)) is determined to be 1.6 x 10(-6) at the 90% confidence level. In addition, a search for eta(1405) -> f(0) (980) pi(0) in psi(3686) radiative decays is performed. No signal is observed, and the branching fraction B(psi(3686) -> gamma eta(1405)) x B(eta(1405) -> f(0)(980)pi(0)) x B(f(0)(980) -> pi(+)pi(-)) is calculated to be less than 5.0 x 10(-7) at the 90% confidence level.

Using a sample of 448.1 x 10(6) Psi(3686) events collected with the BESIII detector in 2009 and 2012, we study the decays chi(c0,2) -> eta 'eta ' and eta eta '. The decays chi(c2) -> eta 'eta ', chi(c0) -> eta eta ' and chi(c2) -> eta eta ' are observed for the first time with statistical significances of 9.6 sigma, 13.4 sigma and 7.5 sigma, respectively. The branching fractions are determined to be B(chi(c0) -> eta 'eta ') = (2.19 +/- 0.03 +/- 0.14) x 10(-3), B(chi(c2) -> eta 'eta ') = (4.76 +/- 0.56 +/- 0.38) x 10(-5), B(chi(c0) -> eta eta ') = (8.92 +/- 0.84 +/- 0.65) x 10(-5) and B(chi(c2) -> eta eta ') = (2.27 +/- 0.43 +/- 0.25) x 10(-5), where the first uncertainties are statistical and the second are systematic. The precision for the measurement of B(chi(c0) -> eta 'eta ') thorn is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for chi(c0,2) decays into pseudoscalar meson pairs can be clarified.

Using a sample of 1.31 x 10(9) J/Psi events collected with the BESIII detector at the BEPCII collider, we study the decays of J/Psi -> KSKL and KSKS. The branching fraction of J/Psi -> KSKL is determined to be B(J/Psi -> KSKL) = (1.93 +/- 0.01 (stat) +/- 0.05 (syst)) x 10(-4), which significantly improves on previous measurements. No clear signal is observed for the J/Psi -> KSKS process, and the upper limit at the 95% confidence level for its branching fraction is determined to be B(J/Psi -> KSKS) < 1.4 x 10(-8), which improves on the previous searches by 2 orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

Using a data set with an integrated luminosity of $2.93\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected at $\sqrt{s}=3.773\text{ }\mathrm{GeV}$ with the BESIII detector operating at the BEPCII storage rings, we search for the rare decay ${D}^{+}\ensuremath{\rightarrow}{D}^{0}{e}^{+}{\ensuremath{\nu}}_{e}$. No signal events are observed. We set the upper limit on the branching fraction for ${D}^{+}\ensuremath{\rightarrow}{D}^{0}{e}^{+}{\ensuremath{\nu}}_{e}$ to be $1.0\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}4}$ at the 90% confidence level.

Using 2.93 fb(-1) of data taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we study the semileptonic decays D+ -> (K) over bar (0)e(+)nu(e) and D+ -> pi(0)e(+)nu(e). We measure the absolute decay branching fractions B(D+ -> (K) over bar (0)e(+)nu(e)) = (8.60 +/- 0.06 +/- 0.15) x 10(-2) and B(D+ -> pi(0)e(+)nu(e)) = (3.63 +/- 0.08 +/- 0.05) x 10(-3), where the first uncertainties are statistical and the second systematic. We also measure the differential decay rates and study the form factors of these two decays. With the values of |V-cs| and |V-cd| from Particle Data Group fits assuming Cabibbo-Kobayashi-Maskawa (CKM) unitarity, we obtain the values of the form factors at q(2) = 0, f(+)(K)(0) = 0.725 +/- 0.004 +/- 0.012, and f(+)(pi)(0) = 0.622 +/- 0.012 +/- 0.003. Taking input from recent lattice QCD calculations of these form factors, we determine values of the CKM matrix elements |V-cs| = 0.944 +/- 0.005 +/- 0.015 +/- 0.024 and |V-cd| = 0.210 +/- 0.004 +/- 0.001 +/- 0.009, where the third uncertainties are theoretical.

The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity-dependent photoabsorption cross sections. The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides a measurement of the generalised GDH integral covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. The contribution of the nucleon-resonance region is seen to decrease rapidly with increasing $Q^2$. The DIS contribution is sizeable over the full measured range, even down to the lowest measured $Q^2$. As expected, at higher $Q^2$ the data are found to be in agreement with previous measurements of the first moment of $g_1$. From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton--neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at $Q^2 = 5$ GeV$^2$.

Two different \(\bar{p}n\) annihilation modes, \(\bar{p}n\rightarrow\pi^{-}4\pi^{0}\) and \(\bar{p}n\rightarrow 2\pi^{-}2\pi^{0}\pi^{+}\), are used to study the 4\(\pi\)–decays of scalar and vector mesons. The data are dominated by 4\(\pi\) scalar isoscalar interactions. At least two states are needed, the \(f_{0}(1370)\) and the \(f_{0}(1500)\). The 4\(\pi\)–decay width of the \(f_{0}(1370)\) is more than 6 times larger than the sum of all observed partial decay widths to two pseudoscalar mesons. The state has important couplings to \((\pi\pi)_{\mathrm{S}}(\pi\pi)_{\mathrm{S}}\) and to \(\rho\rho\). The 4\(\pi\)-decays of the \(f_0\)(1500) represent about half of its total width. The \(\rho(1450)\) and the \(\rho(1700)\) are observed in several 4\(\pi\) decay modes. The ratio of the \(4\pi\) relative to the \(2\pi\) decay of the \(\rho(1450)\) is in contradiction to its proposed interpretation as a pure hybrid state but it suggests that it is not a pure \(2^{3}\rm S_{1}\)–state either. Our results favour the assignment of the \(\rho(1700)\) as \(^{3}\rm D_{1}\) state, its interpretation as \(3^{3}\rm S_{1}\)-state is less plausible.

We have determined branching ratios for antiproton annihilations at rest on protons or neutrons in liquid deuterium which we compare to frequencies of isospin-related processes in antiproton-proton annihilations. Using the annihilation rates into $\pi^0\pi^0$ and $\pi^-\pi^0$ where the annihilation took place on the proton or neutron, respectively, we discuss the fraction of S-wave and P-wave annihilation in liquid D $_2$ . The frequencies for $\pi^-\omega$ and $\rho^-\pi^0$ , and $\pi^-\eta$ and $\pi^-\eta'$ and the corresponding frequencies for $\overline{\mbox p}$ p annihilations are used to determine isoscalar and isovector contributions to the protonium wave function. The isospin decomposition of the annihilating $\overline{\mbox p}$ p system in the $^3$ S $_1$ or $^1$ S $_0$ state is consistent with both, pure $\overline{\mbox p}$ p initial wave function and with the predictions of $\overline{\mbox N}$ N potential models. For the $^3$ P $_0$ state of the $\overline{\mbox p}$ p atom we find consistency with a pure $\overline{\mbox p}$ p system at annihilation while $\overline{\mbox N}$ N potential models predict large $\overline{\mbox n}$ n contributions. We observe $\rho$ - $\omega$ interference in $\overline{\mbox p}$ p $\rightarrow \pi^+\pi^-\eta$ and $\pi^+\pi^-\pi^0$ annihilation which we compare to $\rho$ - $\omega$ interference in $e^+e^-$ annihilation. The interference patterns show striking similarities due to similar phase relations; the interference magnitude depends on the $\omega$ - $\rho$ production ratio. The similarity of the phase in all 3 data sets demonstrates that isovector and isoscalar parts of the protonium ( $\overline{\mbox p}$ p atomic) wave function are relatively real, again in conflict with $\overline{\mbox N}$ N potential models. The annihilation rate for $\overline{\mbox p}$ d $\rightarrow$ K $^-$ K $^0$ p confirms the dominance of the isovector contribution to $\overline{\mbox N}$ N $\rightarrow$ K $\overline{\mbox K}$ annihilations. No complications due to initial state interactions are required by the data. Furthermore, we searched for narrow quasinuclear bound states close to the $\overline{\mbox N}$ N threshold, also predicted by $\overline{\mbox N}$ N potential models, but with negative outcome. We conclude that $\overline{\mbox N}$ N potential models are not suited to provide insight into the dynamics of the annihilation process.

Antiproton–proton annihilation into $\pi^0\eta\eta$ has been studied with the Crystal Barrel spectrometer at CERN at an incident beam momentum of 1.94 GeV/c. The data were taken with a trigger requiring neutral final states. A new isovector state, the $a_2(1660)$ decaying to $\pi^0\eta$ , is observed. In the $\eta\eta$ invariant mass region around 2.1 GeV/ $c^2$ , strong production of a heavy resonance is required, but our analysis does not distinguish between $J^P = 0^+$ , $2^+$ and $4^+$ . The production of the $f_0(1500)$ in reactions in flight is also observed.

Architectures based on multiple layers of thick gas electron multipliers offer an answer to the quest for novel gaseous counters with single photon detection capability able to overcome all the limitations of the present generation of gaseous photon detectors. A systematic R&D programme has been performed to achieve a deep understanding of the characteristics of these multipliers and to optimize their parameters in view of the photon detection application. Recently a new hybrid approach has been considered: an architecture where the last multiplication stage is obtained by using a MICROMEGAS structure. The characteristics of the hybrid detector are discussed an d preliminary results obtained with a first prototype are reported.

Cetin, Serkant Ali (Dogus Author) -- Conference full title: International Conference on Advanced Technology and Particle Physics, ICATPP 2007; Como; Italy; 8 October 2007 through 12 October 2007 -- #nofulltext#

Proceedings of DIS 2007, p.1121-1124, ISBN 978-3-935702-23-2, ISSN 1435-8077

The CERN Axion Solar Telescope (CAST) experiment uses a decommissioned LHC test magnet in conjunction with three different technology X‐ray photon detectors and tracks the sun to look for the elusive axion. Axions or axion‐like particles with a two‐photon interaction can be produced in the Sun by the Primakoff process, according to the theory. In a laboratory magnetic field they can be transformed into X‐rays with energies of a few keV. CAST has been running for about 6 months during 2003 and most of 2004. The first results from the analysis of the 2003 data are presented here. No signal above background was observed, implying an upper limit to the axion to photon coupling gαγγ < 1.16 × 10−10 GeV−1 at 95% CL for mα ⩽ 0.02 eV. This limit is comparable to the limit from stellar energy loss arguments and considerably more restrictive than any previous experiment in this axion mass range.

Hypothetical axion-like particles with a two-photon interaction would be produced in the sun by the Primakoff process. In a laboratory magnetic field they would be transformed into X-rays with energies of a few keV. The CAST experiment at CERN is using a decommissioned LHC magnet as an axion helioscope in order to search for these axion-like particles. The analysis of the 2003 data has shown no signal above the background, thus implying an upper limit to the axion-photon coupling < 1.16*10^{-10} GeV^{-1} at 95% CL for m_{a}

The three reactions $\overline{p}p \rightarrow \pi^0\pi^0\pi^0$ , $\pi^0\pi^0\eta$ and $\pi^0\eta\eta$ in proton-antiproton annihilation in flight at 900 MeV/c are used to search for isoscalar $0^{++}$ and $2^{++}$ mesons in the mass range 1000–2000 MeV, in particular the $f_0(1710)$ . The description of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ data sets requires an isoscalar tensor resonance decaying into $\pi^0\pi^0$ and $\eta\eta$ with a mass of $(1867\pm46)$ MeV and a width of $(385\pm58)$ MeV. The ratio of partial widths $\Gamma(\eta\eta)/\Gamma(\pi\pi)$ is $0.27 \pm 0.10$ . The analyses of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ show no signal for the $f_0(1710)$ . The $\pi^0\eta\eta$ data set shows a strong signal of the $f_2^{\prime}(1525)$ suggesting a large OZI rule violation for tensor meson production in $\overline{p}p$ annihilation. The $\pi^0\pi^0\pi^0$ data set also requires the $f_2(1565)$ . The signal for the $f_2(1810)$ reported by earlier experiments is confirmed neither in $\pi^0\pi^0\pi^0$ nor in $\pi^0\eta\eta$ . The analysis of $\pi^0\pi^0\eta$ leads to an isovector tensor state decaying into $\pi^0\eta$ with a mass of $(1698\pm44)$ MeV and a width of $(265\pm55)$ MeV.

Measurements of the individual multiplicities of pi+, pi- and pi0 produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion multiplicity is the same as for neutral pions, up to approximately z= 0.7, where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below z= 0.7) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is 0.51 +/- 0.01 (stat.) +/- 0.08 (syst.) and 0.26 +/- 0.01 (stat.) +/- 0.04 (syst.), respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer Q^2 and the Bjorken variable x. The observed dependence on Q^2 agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected Q^2-dependence., Comment: Revised version submitted to the European Physical Journal C; 10 pages, 9 figures, 1 table

The influence of the nuclear medium on the production of charged hadrons in semi-inclusive deep-inelastic scattering has been studied by the HERMES experiment at DESY using a 27.5 GeV positron beam. The differential multiplicity of charged hadrons and identified charged pions from nitrogen relative to that from deuterium has been measured as a function of the virtual photon energy \nu and the fraction z of this energy transferred to the hadron. There are observed substantial reductions of the multiplicity ratio R_M^h at low \nu and at high z, both of which are well described by a gluon-bremsstrahlung model of hadronization. A significant difference of the \nu-dependence of R_M^h is found between positive and negative hadrons. This is interpreted in terms of a difference between the formation times of protons and pions, using a phenomenological model to describe the \nu- and z-dependence of R_M^h., Comment: 10 pages, 5 figures, LaTex (RevTeX)