A. Staude

A high statistics measurement of the proton structure functions F2(x, Q2) and R from deep inelastic muon scattering at high Q2

Abstract We present results on a high statistics study of the proton structure functions F 2 ( x , Q 2 ) and R = σ L / σ T measured in deep inelastic scattering of muons on a hydrogen target. The analysis is based on 1.8 × 10 6 events after all cuts, recorded at beam energies of 100, 120, 200 and 280 GeV and covering a kinematic range 0.06 ⩽ x ⩽ 0.80 and 7 GeV 2 ⩽ Q 2 ⩽260 GeV 2 . At small x , we find R to be different from zero in agreement with predictions of perturbative QCD.

The Crystal Barrel spectrometer at LEAR

The crystal Barrel spectrometer used at LEAR, CERN to study the products of pd annihilations is described. A 1380 element array of Csl crystals measures photons from the decay of π0, η, η′ and ω mesons. A segmented drift chamber in a 1.5T magnetic field is used to identify and measure charged particles. A fast on-line trigger on charged and neutral multiplicities and on the invariant mass of secondary particles is available. The performance of the detector is discussed.

Small-angle proton-proton elastic scattering at very high energies (460 GeV2 < s < 2900 GeV2)☆

Abstract We have investigated the above processes at the CERN Intersecting Storage Rings (ISR). Results show a marked change of the slope parameter b ( t , s ) = (d/d t ) ln (d σ /d t ) around − t ≈ 0.10 GeV 2 . The s − and t − dependence of b ( t , s ) have been observed over the interval 460 GeV 2 s 2 and 0.02 GeV 2 t 2 .

A high statistics measurement of the deuteron structure functions F2(x, Q2) and R from deep inelastic muon scattering at high Q2

Abstract We present results on a high statistics study of the nucleon structure functions F2(x, Q2) and R=σL/σT measured in deep inelastic scattering of muons on a deuterium target. The analysis is based on 8×105 events after all cuts, recorded at beam energies of 120, 200 and 280 GeV in the kinematic range 0.06⩽ × ⩽0.80 and 8GeV2⩽Q2⩽260GeV2. Scaling violations observed in the data are in agreement with predictions of perturbative QCD and allow to determine the QCD mass scale parameter Λ.

A comparison of the structure functions F2 of the proton and the neutron from deep inelastic muon scattering at high Q2

Abstract High statistics data on the structure functions F2 of the proton and the deutron measured with the same apparatus in deep inelastic muon scattering are used to study the ratio of structure functions of neutron and proton F2n/F2p and their difference F2p-F2n. Both measurements are consistent with predictions of the quark-parton model and of QCD.

OBSERVATION OF A DIFFRACTION MINIMUM IN THE PROTON-PROTON ELASTIC SCATTERING AT THE ISR

Abstract We have investigated the pp elastic scattering at the CERN Intersecting Storage Rings (ISR). We report results for centre-of-mass scattering angles between 30 and 100 mrad and for centre-of-mass energies of 23.5,30.7, 44.9 and 53 GeV. The elastic differential cross-section shows a diffraction-like shape with a sharp minimum at about t = −1.4 GeV 2 .

A high statistics measurement of the nucleon structure function F2(x,Q2) from deep inelastic muon-carbon scattering at high Q2

Abstract We present results from a high statistics study of the nucleon structure function F 2 ( x , Q 2 ) measured in deep inelastic scattering of muons on carbon in the kinematic range 0.25⩽ x ⩽0.80 and Q 2 ⩾25 GeV 2 . The analysis is based on 1.5×10 6 reconstructed events recorded at beam energies of 120, 200 and 280 GeV. R = σ L / σ T is found to be independent of x in the range 0.25⩽ x ⩽0.07 and 40 GeV 2 ⩽ Q 2 ⩽200 GeV 2 with a mean value R =0.015±0.013 ( stat ) ±0.026 (syst.).

Observation of small angle proton proton elastic scattering at 30 gev and 45 gev center-of-mass energies

Abstract Small angle elastic scattering events have been observed at the CERN Intersecting Storage Rings. Directions of both particles as well as the collision vertex are reconstructed with the help of four sets of spark chambers, two for each of the two arms. The elastic nature of the events is demonstrated by a collinearity requirement. We find values for the (diffraction) slope parameter in disagreement with the simple linear extrapolation of lower energy (Surpukov) data.

Test of QCD and a measurement of Λ from scaling violations in the proton structure function F2(x, Q2) at high Q2

Abstract Scaling violations in the proton structure function F 2 ( x , Q 2 ) measured with high statistics in deep inelastic scattering of muons on a hydrogen target are compared to predictions of perturbative QCD. Excellent agreement is observed with numerical solutions of the evolution equations in leading and next-to-leading order. The QCD mass scale parameter Λ is determined from these data both in a flavour nonsinglet approximation and with a complete flavour singlet and nonsinglet treatment. An estimate of the gluon distribution in the proton is given.

Diffractive production of the charmed baryon Λ+c at the CERN ISR☆

Abstract In a sample of diffractive events of high multiplicity a sharp five standard deviation signal is observed at M = 2255 MeV/c2 in the K−pπ+ mass distribution and, although with less statistical strength, at the same mass in the Λ0π+π+π− channel. These signals are identified as being due to the decay of the charmed baryon Λ+c which is produced with a cross section times branching ratio σcB in the range 0.7−1.8 μb for the K−π+p decay and 0.3−0.7 μb for the Λ-π+π+ π− system.