Observation of events at very high $Q^{2}$ in $e p$ collisions at HERA

Measurements of ep scattering with squared 4-momentum transfer Q~2 up to 35000 GeV~2 are compared with the expectation of the standard deep-inelastic model of lepton-nucleon scattering (DIS). For Q~2 > 15000 GeV~2, N_{obs} =12 neutral current candidate events are observed where the expectation is N_DIS = 4.71 \pm 0.76 events. In the same Q~2 range, N_{obs} =4 charged current candidates are observed where the expectation is N_{DIS} = 1.77 \pm 0.87 events. The probability P(N \geq N_{obs}) that the DIS model signal N fluctuates to N \geq N_{obs} in a random set of experiments is 6 10~{-3} for neutral current and 0.14 for charged current. The difference in the observed and expected number of Neutral Current events is mostly due to events at large masses M = sqrt{xs} in which the positron is backscattered at large y = Q~2/M~2.

Note:

30 pages, latex, 8 Figures Report-no: DESY 97-024

positron p: colliding beams
positron p: deep inelastic scattering
momentum transfer: high
neutral current
charged current
electroweak interaction: validity test
transverse momentum: missing-energy
positron: energy spectrum
angular distribution
spectrum: momentum transfer

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Observation of events at very high Q2Q^{2}Q2 in epe pep collisions at HERA

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Observation of events at very high $Q^{2}$ in $e p$ collisions at HERA