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Register a new userRecent Spectroscopy Results from ZEUS
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Achim Geiser
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Recent results on light hadron spectroscopy are reported, with special emphasis on the evidence for a narrow baryonic state decaying to Ks p and Ks pbar, compatible with the pentaquark state theta^+ observed by fixed target experiments. The data were collected with the ZEUS detector at HERA using an integrated luminosity of 121 pb^-1. The analyses were performed in the central rapidity region of inclusive deep inelastic scattering at an ep centre-of-mass energy of 300-318 GeV. Evidence for a narrow resonance in the Ks p and Ks pbar invariant mass spectrum is obtained, with mass 1521.5 pm 1.5(stat)^{+2.8}_{-1.7}(syst) and width consistent with the experimental resolution. If the Ks p part of the signal is identified with the strange pentaquark theta^+, the Ks pbar part is the first evidence for its antiparticle, thetabar^-. Supporting results on other light hadron resonances are also discussed.
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A summary of recent results from ZEUS is presented. New ZEUS results from HERA-1 data include Structure Functions, QCD fits, analysis of hadronic final states, precision measurements of alpha_s, production of heavy flavor mesons and baryons and studies of diffraction. Results from the new HERA-II running include the measurement of the cross section for polarized charged current events and charm events tagged with the new ZEUS vertex detector.
Hadron spectroscopy is one of the most important physics goals of BESIII. BESIII brings great opportunities to study the XYZ states of charmonium by directly producing the Y states up to 4.6 GeV. High statistics of charmonium decays collected at BESIII provide an excellent place for hunting gluonic excitations and studying the excited baryons. Recent results of light hadron spectroscopy and charmonium spectroscopy from BESIII will be reported.
We present recent results from the BES experiment on the observation of the Y(2175) in $J/psito phi f_0(980) eta$, and $eta(2225)$ in $J/psito gamma phi phi$, and X(1440) in $J/psi$ hadronic decays, together with the new observation of $psi(2S)$ radiative decays and hadronic decays into $nksldb+c.c., ldldbpi^0, ldldbeta$. The effort to search for $J/psi$ decays into $gammagamma$ and invisible decays are also reported.
HERA $ep$ collider provides unique information on the proton structure. High center of mass energy $s=320$ GeV gives access to both the low Bjorken-$x$ domain and regime of high momentum transfers $Q$. Recently the H1 collaboration reported a high precision measurement of the structure function $F_2$ at low $x$ leading to tight constraints on the sea quark and gluon densities. Both the H1 and ZEUS collaborations measure the structure function $F_L$ which provides an important cross check of the conventional QCD picture. This measurement is recently extended by H1 to low $Q^2$ where small $x$ corrections may play important role. An ultimate precision of the deep inelastic scattering cross section measurement is achieved by combining the measurements of the H1 and ZEUS collaborations. The combined data are used as a sole input to a QCD fit to obtained HERA PDF set. New measurements of inclusive $e^-p$ neutral and charged current scattering cross sections by the ZEUS collaboration at high $Q^2$ improve precision in this kinematic domain. H1 analysis of the DIS high $P_t$ jet production cross section is used for a determination of the strong coupling constant $alpha_S$. Separation of the strange quark density from the total sea is obtained by the HERMES collaboration using tagged $K^{pm}$ production.
The review on experimental results on charmonium and charmonium-like spectroscopy from B-factories is presented. Main theoretical interpretations, such as conventional charmonium, molecular state, hybrids, tetraquarks and others are discussed.
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