We investigate the four-photon final state produced in γγ colissions. In the π 0 π 0 channel we observe f(1270) production with predominantly helicity 2 and measure a partial width Γ γγ 2.9 +0.6 −0.4 ± keV (independent of assumptions on the helicity). We observe A 2 (1310) production in the π 0 η channel and find a partial width Γ γγ = 0.77 ± 0.18 ± 0.27 KeV (assuming helicity 2). We give an upper limit for f ≈ ηη .
Data read from graph. Systematic error on M is of order of 2% or less.
No description provided.
Using 2674 nb−1 of data taken at s from 5.00 to 7.25 GeV with a trigger sensitive to decays of lower-mass particles produced in two-photon collisions, we have observed 56±12 events consistent with the reaction e+e−→e+e−η, η→γγ. Background has been subtracted using separated-beam data. We obtain Γγγ(η)=0.56±0.16 keV and the pseudoscalar-nonet mixing angle θP=−17.6°±3.6°.
No description provided.
We have measured the inclusive cross section for η production in e+e− interactions near charm threshold using the Crystal Ball detector. No pronounced structure in the energy dependence is observed. By comparing cross sections above and below charm threshold we obtain the limits (90% confidence limit): R(e+e−→FF¯X)RB(F→ηx)<0.15−0.32 (for Ec.m. from 4.0 to 4.5 GeV), RB(D→ηx)<0.13. Our results are inconsistent with a previous report of a large energy dependence of the η cross section ascribed to the crossing of the FF* and F*F* production thresholds.
Axis error includes +- 0.0/0.0 contribution (?////DECAY PI0 --> 2GAMMA//RES-DEF(RES=ETA,BACK=CORRECTED,DEF=340 < M( 2GAMMA ) < 800 MEV)//DECAY-BR(BRN=ETA --> 2GAMMA,BR=38 PCT)).
THE 4.028 GEV DATA ARE NOT INCLUDED IN THE 4.005-4.082 GEV BIN. Axis error includes +- 0.0/0.0 contribution (?////DECAY PI0 --> 2GAMMA//RES-DEF(RES=ETA,BACK=CORRECTED,DEF=340 < M( 2GAMMA ) < 800 MEV)//DECAY-BR(BRN=ETA --> 2GAMMA,BR=38 PCT)).
AT FIXED ENERGIES.
Inclusive cross sections are presented for 2π and 3π systems with large longitudinal x at the highest intersecting storage ring energies (s=53 GeV for 2π; s=53 and 62 GeV for 3π). The ratio π+π−π−π− rises sharply with increasing x similar to the ratio K+K−, as expected in a quark-model interpretation.
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D* cross sections.
abstract only
No description provided.
No description provided.
No description provided.
We present evidence for the exclusive reaction e+e−→Ds±Ds*∓, observed with the Mark III detector at the SLAC storage ring SPEAR. The Ds± is reconstructed in the φπ± decay mode, while the Ds*∓ is detected as a narrow peak in the recoil-mass distribution. The mass of the Ds* is found to be 2109.3±2.1±3.1 MeV/c2, yielding a Ds*−Ds mass difference of 137.9±2.1±4.3 MeV/c2. The width of the Ds* is <22 MeV/c2 at the 90%-confidence level. The observed signal corresponds to σ(e+e−→Ds+Ds*−+Ds−Ds*+)B(Ds+→φπ+)=30±6±11 pb at s=4.14 GeV.
No description provided.
Inclusive measurements of Λ 0 , Λ 0 , Ξ − , Σ(1385) ± ) production in the forward direction at the CERN intersecting storage rings are presented. A signal for simulataneous Λ 0 Λ 0 production is also observed with total x > 0.6, 2.3 < M Λ Λ < 2.5 GeV and with a cross section of (1.7 ± 0.2) μb.
No description provided.
No description provided.
A search for new long-lived particles decaying to leptons is presented using proton-proton collisions produced by the LHC at sqrt(s) = 8 TeV. Data used for the analysis were collected by the CMS detector and correspond to an integrated luminosity of 19.7 inverse femtobarns. Events are selected with an electron and a muon that have transverse impact parameter values between 0.02 cm and 2 cm. The search has been designed to be sensitive to a wide range of models with nonprompt e-mu final states. Limits are set on the "displaced supersymmetry" model, with pair production of top squarks decaying into an e-mu final state via R-parity-violating interactions. The results are the most restrictive to date on this model, with the most stringent limit being obtained for a top squark lifetime corresponding to c tau = 2 cm, excluding masses below 790 GeV at 95% confidence level.
Numbers of expected and observed events in the three search regions (see the text for the definitions of these regions). Background and signal expectations are quoted as $N_{\text{exp}} \pm 1\sigma$ stat $\pm 1\sigma$ syst. If the estimated background is zero in a particular search region, the estimate is instead taken from the preceding region. Since this should always overestimate the background, we denote this by a preceding "<".
Expected and observed 95% CL cross section exclusion contours for top squark pair production in the plane of top squark lifetime ($c\tau$) and top squark mass. These limits assume a branching fraction of 100\% through the RPV vertex $\tilde{t}$ $\to$ b l, where the branching fraction to any lepton flavor is equal to 1/3. As indicated in the plot, the region to the left of the contours is excluded by this search.
Electron reconstruction efficiency as function of its tranverse impact parameter, $d_0$.
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