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Register a new userFirst observation of $gamma gamma to p bar{p} K^+ K^-$ and search for exotic baryons in $pK$ systems
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The process $gamma gamma to p bar{p} K^+ K^-$ and its intermediate processes are measured for the first time using a 980~fb$^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The production of $p bar{p} K^+ K^-$ and a $Lambda(1520)^0~(bar{Lambda}(1520)^0)$ signal in the $pK^-$~($bar{p} K^+$) invariant mass spectrum are clearly observed. However, no evidence for an exotic baryon near 1540~MeV/$c^2$, denoted as $Theta(1540)^0$~($bar{Theta}~(1540)^0$) or $Theta(1540)^{++}$~($Theta(1540)^{--}$), is seen in the $p K^-$~($bar{p}K^+$) or $pK^+$~($bar{p} K^-$) invariant mass spectra. Cross sections for $gamma gamma to p bar{p} K^+ K^-$, $Lambda(1520)^0 bar{p} K^+ +c.c.$ and the products $sigma(gamma gamma to Theta(1540)^0 bar{p} K^+ +c.c.)BR(Theta(1540)^0 to p K^{-})$ and $sigma(gamma gamma to Theta(1540)^{++} bar{p} K^- +c.c.)BR(Theta(1540)^{++}to p K^{+})$ are measured. We also determine upper limits on the products of the $chi_{c0}$ and $chi_{c2}$ two-photon decay widths and their branching fractions to $p bar{p} K^+ K^-$ at the 90% credibility level.
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The exclusive reactions $gamma p to bar K^0 K^+ n$ and $gamma p to bar K^0 K^0 p$ have been studied in the photon energy range 1.6--3.8 GeV, searching for evidence of the exotic baryon $Theta^+(1540)$ in the decays $Theta^+to nK^+$ and $Theta^+to p K^0$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The integrated luminosity was about 70 pb$^{-1}$. The reactions have been isolated by detecting the $K^+$ and proton directly, the neutral kaon via its decay to $K_S to pi^+ pi^-$ and the neutron or neutral kaon via the missing mass technique. The mass and width of known hyperons such as $Sigma^+$, $Sigma^-$ and $Lambda(1116)$ were used as a check of the mass determination accuracy and experimental resolution. Approximately 100,000 $Lambda^*(1520)$s and 150,000 $phi$s were observed in the $bar K^0 K^+ n$ and $bar K^0 K^0 p$ final state respectively. No evidence for the $Theta^+$ pentaquark was found in the $nK^+$ or $pK_S$ invariant mass spectra. Upper limits were set on the production cross section of the reaction $gamma p to Theta^+ bar K^0$ as functions of center-of-mass angle, $nK^+$ and $pK_S$ masses. Combining the results of the two reactions, the 95% C.L. upper limit on the total cross section for a resonance peaked at 1540 MeV was found to be 0.7 nb. Within most of the available theoretical models, this corresponds to an upper limit on the $Theta^+$ width, $Gamma_{Theta^{+}}$, ranging between 0.01 and 7 MeV.
A search for a narrow baryonic state in the $pK^0_S$ and $bar{p}K^0_S$ system has been performed in $ep$ collisions at HERA with the ZEUS detector using an integrated luminosity of 358 pb$^{-1}$ taken in 2003-2007. The search was performed with deep inelastic scattering events at an $ep$ centre-of-mass energy of 318 GeV for exchanged photon virtuality, $Q^2$, between 20 and 100 $rm{} GeV^{2}$. Contrary to evidence presented for such a state around 1.52 GeV in a previous ZEUS analysis using a sample of 121 pb$^{-1}$ taken in 1996-2000, no resonance peak was found in the $p(bar{p})K^0_S$ invariant-mass distribution in the range 1.45-1.7 GeV. Upper limits on the production cross section are set.
The exclusive reaction $gamma p to bar K^0 K^+ n$ was studied in the photon energy range between 1.6-3.8 GeV searching for evidence of the exotic baryon $Theta^+(1540)to nK^+$. The decay to $nK^+$ requires the assignment of strangeness $S=+1$ to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 $pb^{-1}$. No evidence for the $Theta^+$ pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and $nK^+$ mass. The 95% CL upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.
The first observation of the decay $eta_{c}(2S) to p bar p$ is reported using proton-proton collision data corresponding to an integrated luminosity of $3.0rm , fb^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $eta_{c}(2S)$ resonance is produced in the decay $B^{+} to [cbar c] K^{+}$. The product of branching fractions normalised to that for the $J/psi$ intermediate state, ${cal R}_{eta_{c}(2S)}$, is measured to be begin{align*} {cal R}_{eta_{c}(2S)}equivfrac{{mathcal B}(B^{+} to eta_{c}(2S) K^{+}) times {mathcal B}(eta_{c}(2S) to p bar p)}{{mathcal B}(B^{+} to J/psi K^{+}) times {mathcal B}(J/psito p bar p)} =~& (1.58 pm 0.33 pm 0.09)times 10^{-2}, end{align*} where the first uncertainty is statistical and the second systematic. No signals for the decays $B^{+} to X(3872) (to p bar p) K^{+}$ and $B^{+} to psi(3770) (to p bar p) K^{+}$ are seen, and the 95% confidence level upper limits on their relative branching ratios are % found to be ${cal R}_{X(3872)}<0.25times10^{-2}$ and ${cal R}_{psi(3770))}<0.10$. In addition, the mass differences between the $eta_{c}(1S)$ and the $J/psi$ states, between the $eta_{c}(2S)$ and the $psi(2S)$ states, and the natural width of the $eta_{c}(1S)$ are measured as begin{align*} M_{J/psi} - M_{eta_{c}(1S)} =~& 110.2 pm 0.5 pm 0.9 rm , MeV, M_{psi(2S)} -M_{eta_{c}(2S)} =~ & 52.5 pm 1.7 pm 0.6 rm , MeV, Gamma_{eta_{c}(1S)} =~& 34.0 pm 1.9 pm 1.3 rm , MeV. end{align*}
We report the study of OK and SK using a $772 times 10^6$ $Bbar{B}$ pair data sample recorded on the $Upsilon({rm 4S})$ resonance with the Belle detector at KEKB. The following branching fractions are measured: $mathcal{B}$(OKPHSP) $=$ $(4.22^{+0.45}_{-0.44}pm 0.51)times10^{-6}$, $mathcal{B}$(SKPHSP) $=$ $(3.81^{+0.39}_{-0.37} pm 0.45)times 10^{-6}$, $mathcal{B}$(ETACD+c.c.) $=$ $(2.91^{+0.37}_{-0.35}pm 0.36)times 10^{-3}$ and $mathcal{B}$(PLPHI) $=$ $(8.18 pm 2.15 pm 0.79)times10^{-7}$, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also found evidences for $mathcal{B}$(ETACS+c.c.) $=$ $(3.59 pm 1.52 pm 0.47) times 10^{-3}$ and $mathcal{B}$(LLKO) $=$ $(2.30 pm 0.65 pm 0.25) times 10^{-6}$. No significant signals are found for JPSIS+c.c. and LLKS ; we set the 90% confidence level upper limits on their decay branching fractions as $< 1.85times10^{-3}$ and $< 2.14times10^{-6}$, respectively.
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