The Z Charmoniumlike Mesons
A brief review of the experimental situation concerning the electrically-charged charmoniumlike meson candidates, $Z^-$, is presented.
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arXiv subjects
Arafat Gabareen Mokhtar
Publications and source records attributed to Arafat Gabareen Mokhtar.
Search for the xi(2220) and Study of the X(3872) at BABAR
The BABAR Collaboration performed a search for xi(2220) production in the initial-state radiation process e^+e^- --> gamma J/psi, J/psi --> gamma K^+K^- or J/psi --> gamma K^0_SK^0_S. No evidence for the xi(2220) resonance has been found. The 90% confidence level upper limits on the product of branching fractions are sensitive to the spin and helicity hypotheses. These upper limits are of the order 10^-5, below the values reported in previous experiments. Also at BABAR, the decays B --> J/psi pi^+ pi^- pi^0 K are studied to search for the decay X(3872) --> J/psi omega. This search yields a four standard deviation evidence for X(3872) --> J/psi omega, with product branching fractions of B(B^+ --> X(3872)K^+) x B(X(3872) --> J/psi omega)=[0.6 +- 0.2(stat) +- 0.1(syst) ] x 10^-5, and B(B^0 --> X(3872)K^0) x B(X(3872) --> J/psi omega =[0.6 +- 0.3(stat) +- 0.1(syst) ] x 10^-5. A detailed study of the pi^+ pi^- pi^0 mass distribution from X(3872) decay favors a negative-parity assignment but does not rule out the positive-parity hypothesis.
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Studies of charmonium-like states at BABAR
Several charmonium-like states above $D\bar{D}$ threshold have been discovered at the Belle and BABAR B-factories. Some of these states are produced via Initial State Radiation (e.g. Y(4260) and Y(4350)), and some are observed in B-meson decays (e.g. X(3872), and Y(3940)). The Belle observations of the enhancements in the $ψ(2S)π^-$ and $χ_{c1}π^-$, i.e. the Z(4430)-, Z_1(4050)-, and Z_2(4250)-, have generated a great deal of interest, because such states must have minimum quark content $(c\bar{c}d\bar{u})$, i.e. these are candidate four-quark state. The BABAR Collaboration does not confirm the existinence of the $Z(4430)^-$.
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Search for a low-mass Higgs boson ($A^0$) at BABAR
The BABAR Collaboration has performed three searches for a light Higgs boson, $A^0$, in radiative Upsilon ($Υ$) decays: $Υ(3S)\toγA^0$, $A^0\toτ^+τ^-$; $Υ(nS)\toγA^0$, $A^0\toμ^+μ^-$ ($n=2,3$); and $Υ(3S)\toγA^0$, $A^0\to$ invisible. Such a Higgs boson ($A^0$) appears in the Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson couples strongly to $b$-quarks. The searches are based on data samples that consist of $122\times 10^6$ $Υ(3S)$ and $99\times 10^6$ $Υ(2S)$ decays, collected by the BABAR detector at the SLAC National Accelerator Laboratory. The searches reveal no evidence for an $A^0$, and product of branching fractions upper limits, at 90% C.L., of $(1.5-16)\times 10^{-5}$, $(0.44-44)\times 10^{-6}$, and $(0.7-31)\times 10^{-6}$ were obtained for these searches, respectively. Also, we set the upper limits ${\mathcal {B}}(η_b\toτ^+τ^-)<8%$ and ${\mathcal {B}}(η_b\toμ^+μ^-)<0.9%$.
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Searches for exotic X,Y, and Z- states with BABAR
Recently, several charmonium-like states above $D\bar{D}$ threshold have been discovered at the BELLE and BABAR $B$-factories. Some of these states are produced via Initial State Radiation ({\it e.g.} Y(4260) and Y(4350)) and some are observed in $B$ meson decays ({\it{e.g.}} X(3872), Y(3940)). The BELLE observation of the enhancement in the $ψ(2S)π^-$, {\it {i.e.}} the $Z(4430)^-$ state, has generated a great deal of interest, because such a state must have minimum quark content ($c\bar{c}d\bar{u}$), so that it would represent the unequivocal manifestation of a four-quark meson state. Here we report recent BABAR results on the Y(4260), X(3872), Y(3940), and a search for the $Z(4430)^-$.
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Charmonium spectroscopy at BABAR
The charmonium-like states, Y(4260), Y(4350), produced via initial state radiation, as well as the X(3872), and Y(3940), produced in B meson decays from the BABAR B-factory are reviewed. These mesons do not seem consistent with conventional charmonium models, and several alternate hypotheses have been proposed to explain these new discoveries.
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Recent Electroweak Measurements from the H1 and ZEUS Experiments
Neutral-current ({NC}) and charged-current ({CC}) deep inelastic scattering ({DIS}) reactions have been studied in $e^+p$ and $e^-p$ collisions using the {H1} and {ZEUS} detectors at {HERA I}. Following the upgrade of the {HERA} accelerator, the {HERA II} program recently started with the first data in $e^+p$ scattering with longitudinally polarised positrons. In this paper, a summary of the electroweak results from {HERA I} and the first measurement of the cross section for $e^+p$ CC {DIS} at a longitudinal polarisation value of 33% from the {ZEUS} collaboration are presented.
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