The production of jets is studied in deep-inelastic e(+) p scattering at low negative four momentum transfer squared 5 < Q(2) < 100 GeV2 and at inelasticity 0.2 < y < 0.7 using data recorded by the ...H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb(-1). Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q(2) and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction xi. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling as.
A search for physics beyond the Standard Model in neutral current deep inelastic scattering at high negative four-momentum transfer squared Q(2) is performed in e(+/-)p collisions at HERA. The ...differential cross section d sigma/dQ(2), measured using the full H1 data sample corresponding to an integrated luminosity of 446 pb(-1), is compared to the Standard Model prediction. No significant deviation is observed. Limits on various models predicting new phenomena at high Q(2) are derived. For general four-fermion eeqq contact interaction models, lower limits on the compositeness scale A are set in the range 3.6 TeV to 7.2 TeV. Leptoquarks with masses M-LQ and couplings lambda are constrained to M-LQ/lambda > 0.41-1.86 TeV and limits on squarks in R-parity violating supersymmetric models are derived. A lower limit on the gravitational scale in 4 + n dimensions of M-S > 0.9 TeV is established for low-scale quantum gravity effects in models with large extra dimensions. For the light quark radius an upper bound of R-q < 0.65 . 10(-18) m is determined. (C) 2011 Elsevier B.V. All rights reserved.
Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling ...variable
x
>
10
-
3
, the inelasticity
0.2
<
y
<
0.7
and the photon virtuality
150
<
Q
2
<
15000
GeV
2
. The search is performed using H1 data corresponding to an integrated luminosity of 351 pb
-
1
. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between 1.5 and 6 pb, at
95
%
confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging predictions.
A first measurement is presented of exclusive photoproduction of
ρ
0
mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a ...centre-of-mass energy of
s
=
319
GeV and correspond to an integrated luminosity of 1.16 pb
-
1
. The
ρ
0
mesons with transverse momenta
p
T
<
1
GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum,
x
L
>
0.35
, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality
Q
2
<
2
GeV
2
, the total energy of the photon–proton system
20
<
W
γ
p
<
100
GeV and the polar angle of the leading neutron
θ
n
<
0.75
mrad. The cross section of the reaction
γ
p
→
ρ
0
n
π
+
is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a
ρ
0
meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering,
σ
el
(
γ
π
+
→
ρ
0
π
+
)
, is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction
γ
p
→
ρ
0
n
π
+
.
The H1 forward proton spectrometer at HERA van Esch, P.; Kapichine, M.; Morozov, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2000, Letnik:
446, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The forward proton spectrometer is part of the H1 detector at the HERA collider. Protons with energies above 500
GeV and polar angles below 1
mrad can be detected by this spectrometer. The main ...detector components are scintillating fiber detectors read out by position-sensitive photo-multipliers. These detectors are housed in the so-called Roman Pots which allow them to be moved close to the circulating proton beam. Four Roman Pot stations are located at distances between 60 and 90
m from the interaction point.
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