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.
A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep→μX and ep→τX is performed by the H1 experiment at HERA. ...The full data sample taken at a centre-of-mass energy s=319 GeV is used for the analysis, corresponding to an integrated luminosity of 245 pb−1 of e+p and 166 pb−1 of e−p collision data. No evidence for the production of such leptoquarks is observed in the H1 data. Leptoquarks produced in e±p collisions with a coupling strength of λ=0.3 and decaying with the same coupling strength to a muon–quark pair or a tau–quark pair are excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479 GeV, respectively.
Deep-inelastic positron-proton scattering events at low photon virtuality,
Q
2
, with a forward jet, produced at small angles with respect to the proton beam, are measured with the H1 detector at ...HERA. A subsample of events with an additional jet in the central region is also studied. For both samples, differential cross sections and normalised distributions are measured as a function of the azimuthal angle difference, Δ
ϕ
, between the forward jet and the scattered positron in bins of the rapidity distance,
Y
, between them. The data are compared to predictions of Monte Carlo generators based on different evolution approaches as well as to next-to-leading order calculations in order to test the sensitivity to QCD evolution mechanisms.
Measurements of cross sections for events with charm and beauty jets in deep inelastic scattering at HERA are presented. Events with jets of transverse energy
GeV and pseudorapidity −1.0<
η
jet
<1.5 ...in the laboratory frame are selected in the kinematic region of photon virtuality
Q
2
>6 GeV
2
and inelasticity variable 0.07<
y
<0.625. Measurements are also made requiring a jet in the Breit frame with
GeV. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb
−1
. The numbers of charm and beauty jets are determined using variables reconstructed using the H1 vertex detector with which the impact parameters of the tracks to the primary vertex and the position of secondary vertices are measured. The measurements are compared with QCD predictions and with previous measurements where heavy flavours are identified using muons.
The inclusive production of D*(+/-)(2010) mesons in deep-inelastic e(+/-)p scattering is measured in the kinematic region of photon virtuality 100 < Q(2) < 1000 GeV2 and inelasticity 002 < y < 0 7 ...Single and double differential cross sections for inclusive D* meson production are measured in the visible range defined by vertical bar eta(D*)vertical bar < 1 5 and p(gamma)(D*) > 1 5 GeV The data were collected by the H1 experiment during the period from 2004 to 2007 and correspond to an integrated luminosity of 351 pb(-1) The charm contribution. F-2(c (c) over bar), to the proton structure function F-2 is determined. The measurements are compared with QCD predictions. (C) 2010 Elsevier B V All rights reserved
The production of photons at very small angles with respect to the proton beam direction is studied in deep-inelastic positron–proton scattering at HERA. The data are taken with the H1 detector in ...the years 2006 and 2007 and correspond to an integrated luminosity of 126 pb
−1
. The analysis covers the range of negative four momentum transfer squared at the positron vertex 6<
Q
2
<100 GeV
2
and inelasticity 0.05<
y
<0.6. Cross sections are measured for the most energetic photon with pseudorapidity
η
>7.9
as a function of its transverse momentum
and longitudinal momentum fraction of the incoming proton
. In addition, the cross sections are studied as a function of the sum of the longitudinal momentum fraction
of all photons in the pseudorapidity range
η
>7.9. The cross sections are normalised to the inclusive deep-inelastic scattering cross section and compared to the predictions of models of deep-inelastic scattering and models of the hadronic interactions of high energy cosmic rays.
A search for squarks in
R
-parity violating supersymmetry is performed in
e
±
p
collisions at HERA using the H1 detector. The full data sample taken at a centre-of-mass energy
GeV is used for the ...analysis, corresponding to an integrated luminosity of 255 pb
−1
of
e
+
p
and 183 pb
−1
of
e
−
p
collision data. The resonant production of squarks via a Yukawa coupling
λ
′ is considered, taking into account direct and indirect
R
-parity violating decay modes. Final states with jets and leptons are investigated. No evidence for squark production is found and mass dependent limits on
λ
′ are obtained in the framework of the Minimal Supersymmetric Standard Model and in the Minimal Supergravity Model. In the considered part of the parameter space, for a Yukawa coupling of electromagnetic strength
λ
′=0.3, squarks of all flavours are excluded up to masses of 275 GeV at 95% confidence level, with down-type squarks further excluded up to masses of 290 GeV.
A new measurement of the proton structure function
F2 (
x,
Q
2) is reported for momentum transfers squared
Q
2 between .5 GeV
2 and 5000 GeV
2 and for Bjorken
x between 3 · 10
−5 and 0.32 using data ...collected by the HERA experiment H1 in 1994. The data represent an increase in statistics by a factor of ten with respect to the analysis of the 1993 data. Substantial extension of the kinematic range towards low
Q
2 and
x has been achieved using dedicated data samples and events with initial state photon radiation. The structure function is found to increase significantly with decreasing x, even in the lowest accessible
Q
2 region. The data are well described by a Next to Leading Order QCD fit and the gluon density is extracted.
A
BSTRACT
Inclusive
e
±
p
single and double differential cross sections for neutral and charged current deep inelastic scattering processes are measured with the H1 detector at HERA. The data were ...taken at a centre-of-mass energy of
GeV with a total integrated luminosity of 333.7 pb
−1
shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared,
Q
2
, between 60 and 50 000 GeV
2
, and Bjorken
x
between 0
.
0008 and 0
.
65. The measurements are combined with earlier published unpolarised H1 data to improve statistical precision and used to determine the structure function
. Ameasurementoftheneutralcurrentparityviolating structure function
is presented for the first time. The polarisation dependence of the charged current total cross section is also measured. The new measurements are well described by a next-to-leading order QCD fit based on all published H1 inclusive cross section data which are used to extract the parton distribution functions of the proton.
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