No abstract

No abstract

The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high{resolution lead/scintillating{ bre calorimeter.The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out{of{time background events at the rst trigger level. It must be compact due to space restrictions.These requirements were ful lled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic bres embedded in a lead matrix. Its lead{to{ bre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter bres with a lead{to{ bre ratio of 3.4:1.The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.

Abstract:The results of a measurement of the proton structure function F 2 (x, Q 2 ) and the virtual photon-proton cross section are reported for momentum transfers squared Q 2 between 0.35 GeV 2 and 3.5 GeV 2 and for Bjorken-x values down to 6 · 10 −6 using data collected by the HERA experiment H1 in 1995. The data represent an increase in kinematic reach to lower x and Q 2 values of about a factor of 5 compared to previous H1 measurements. Including measurements from fixed target experiments the rise of F 2 with decreasing x is found to be less steep for the lowest Q 2 values measured. Phenomenological models at low Q 2 are compared with the data.

No abstract