We report the first observation of charmed mesons with the ZEUS detector at HERA using the decay channel ${\rm D}~{*+}\rightarrow (\Do \rightarrow {\rm K}~-\pi~+)\pi~+$ (+ c.c.). Clear signals in the mass difference $\Delta M$=$M$(D$~*$)--$M$(D$~0)$ as well as in the $M(K\pi)$ distribution at the D$~0$ mass are found. The $ep$ cross section for inclusive \DSpm\ production with $Q~2<4\GeV~2$ in the $\gamma p$ centre-of-mass energy range $115 < W < 275$ \GeV\ has been determined to be $(32 \pm 7~{+4}_{-7} )$ nb in the kinematic region \mbox{\{$p_T(\DS)\geq $ 1.7 \,\GeV, $|\eta(\DS)| < 1.5 $\}}. Ex\-tra\-po\-la\-ting outside this region, assuming a mass of the charm quark of 1.5 \GeV, we estimate the $ep$ charm cross section to be $\sigma(e p \rightarrow c \bar{c}X ) = (0.45 \pm 0.11~{+0.37}_{-0.22}) \, \mu {\rm b} $ at \mbox{$\sqrt{s} = 296$}\GeV\ and $\langle W \rangle = 198$ \GeV. The average $\gamma p$ charm cross section \mbox{$\sigma(\gamma p \rightarrow c \bar{c}X )$} is found to be \mbox{$(6.3 \pm 2.2~{+6.3}_{-3.0}) \, \mu {\rm b} $} at $\langle W \rangle = 163$ \GeV\ and \mbox{$(16.9 \pm 5.2~{+13.9}_{-8.5}) \, \mu {\rm b} $} at $\langle W \rangle = 243$ \GeV. The increase of the total charm photoproduction cross section by one order of magnitude with respect to low energy data experiments is well described by QCD NLO calculations using singular gluon distributions in the proton.
No description provided.
Assumes probability of charmed quark pair fragmenting to D* is (55.2 +- 4.2) pct and mass of CQ is 1.5 GeV.
Assumes probability of charmed quark pair fragmenting to D* is (55.2 +- 4.2) pct and mass of CQ is 1.5 GeV.
The photon structure function F 2 γ has been measured at average Q 2 values of 73 and 390 GeV 2 using data collected by the AMY detector at the TRISTAN e + e − collider. F 2 γ is observed to be increasing as ln Q 2 . The x -dependence of F 2 γ , where x is the momentum fraction carried by the parton inside the photon, is also measured. The measurements are compared with several parton density models.
No description provided.
No description provided.
Errors contain both statistics and systematics.
We have used 19 pb**-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at 95% confidence level models containing the following new particles: axigluons with mass between 200 and 870 GeV, excited quarks with mass between 80 and 570 GeV, and color octet technirhos with mass between 320 and 480 GeV.
Here UNSPEC refers to axigluons, excited quarks, colour octet technirhos, ngauge bosons (W' and Z') and diquarks (D and Dc). M is the mass of the new particle (axigluon, q*, ...). Measurements are given to the 95% confidence limit.
We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.
The data are compared to the predictions of Monte-Carlo.
Using the p-scheme for jet clustering.
Using the E-scheme for jet clustering.
Charged particle production has been measured in Deep Inelastic Scattering (DIS) events using the ZEUS detector over a large range of $Q~2$ from 10 to $1280 {\rm\ GeV}~2$. The evolution with $Q$ of the charged multiplicity and scaled momentum has been investigated in the current fragmentation region of the Breit frame. The data are used to study QCD \linebreak coherence effects in DIS and are compared with corresponding \eedata in order to test the universality of quark fragmentation.
Mean charged multiplicity in the current fragmentation region.
Mean charged multiplicity in the current fragmentation region.
Mean charged multiplicity in the current fragmentation region.
A set of two natural abundance Ge detectors of 1.1 kg each, located in the Homestake mine, and one small, 0.253 kg, Ge detector operating in the Canfranc railway tunnel in Spain, have been used to obtain bounds on the stability of the electron against the decay modes e − → γν e and e − → ν e ν e ν e . The bounds on the mean lifes are τ ( γν e ) > 3.7(2.1) × 10 25 yr , 68%(90%) CL and τ(ν e ν e ν e > 4.3(2.6) × 10 23 yr , 68%(90%) CL, which are at present the most stringent laboratory limits for these decays.
Lifetime in years (YR).
We have observed five new decay modes of the charmed baryon Λc+ using data collected with the CLEO II detector. Four decay modes, Λc+→pK¯0η, Ληπ+, Σ+η, and Σ*+η, are first observations of final states with an η meson, while the fifth mode, Λc+→ΛK¯0K+, requires the creation of an ss¯ quark pair. We measure the branching fractions of these modes relative to Λc+→pK−π+ to be 0.25±0.04±0.04, 0.35±0.05±0.06, 0.11±0.03±0.02, 0.17±0.04±0.03, and 0.12±0.02±0.02, respectively.
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
Integrated luminosity of 3.25 fb-1 have used, which corresponds to about 4 million C CBAR events.. Here X=P(LAMBDA/C)/sqrt(Ebeam**2-M(LAMBDA/C)**2).
We present a comparison of the strong couplings of light ($u$, $d$, and $s$), $c$, and $b$ quarks determined from multijet rates in flavor-tagged samples of hadronic $Z~0$ decays recorded with the SLC Large Detector at the SLAC Linear Collider. Flavor separation on the basis of lifetime and decay multiplicity differences among hadrons containing light, $c$, and $b$ quarks was made using the SLD precision tracking system. We find: $\alpha_s{_{\vphantom{y}}}~{uds}/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 0.987 \pm 0.027({\rm stat}) \pm 0.022({\rm syst}) \pm 0.022({\rm theory})$, $\alpha_s{_{\vphantom{y}}}~c/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.012 \pm 0.104 \pm 0.102 \pm 0.096$, and $\alpha_s{_{\vphantom{y}}}~b/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.026 \pm 0.041 \pm 0.041\pm 0.030.$
No description provided.
Using a silicon-microstrip detector array to identify secondary vertices, we have observed b→J/ψ→μ+μ− decays in 800GeV/c proton-gold interactions. The doubly differential cross section for J/ψ mesons originating from b-quark decays, assuming linear dependence on nucleon number, is d2σ/dxFdpT2=107±28±19[pb/(GeV/c)2]/nucleon at xF=0.05 and pT=1GeV/c. This measurement is compared to next-to-leading-order QCD predictions. The integrated b-quark production cross section, obtained by extrapolation over all xF and pT, is σ(pN→bb¯+X)=5.7±1.5±1.3 nb/nucleon.
All J/PSI(1S) are from B/BBAR decays. Cross section per nucleon was obtained with linear A-dependence.
Cross section per nucleon was obtained with linear A-dependence.
All J/PSI(1S) are from B/BBAR decays. Cross section per nucleon was obtained with linear A-dependence. Extrapolation in the XL=0.05 and PT=1 GEV bin.
Using data collected by the CLEO II detector, we have observed two states decaying to Λc+π+π−. Relative to the Λc+, their mass splittings are measured to be +307.5±0.4±1.0 and +342.2±0.2±0.5MeV/c2, respectively; this represents the first measurement of the less massive state. These two states are consistent with being orbitally excited, isospin zero Λc+ states.
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(Z) = FD(Z) = const * (1/Z)*1/(1 - (1/Z)-CONST(NAME=EPS)/(1-Z))**2. Charged conjugated states are understood.
Charged conjugated states are understood.
Charged conjugated states are understood.
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