-
N. Agafonov,
A. Aleksandrov,
O. Altinok,
M. Ambrosio,
A. Anokhina,
S Aoki,
A. Ariga,
T Ariga,
D. Autiero,
A. Badertscher, [......],
G. Wilqueta,
B. Wonsak,
V. Yakushev,
C.S. Yoona,
J Yoshida,
T Yoshioka,
Y. Zaitsev,
S. Zemskova,
A Zghiche,
R Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) has been designed to perform the first detection of neutrino oscillations in direct appearance mode through the study of the $\nu_\mu\rightarrow\nu_\tau$ channel. The hybrid apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2008 and 2009. After a brief description of the beam, the experimental setup and the procedures used for the analysis of the neutrino events, we describe the topology and kinematics of a first candidate $\nu_\tau$ charged-current event satisfying the kinematical selection criteria. The background calculations and their cross-check are explained in detail and the significance of the event is assessed.
Physics Letters B 12/2012; · 3.95 Impact Factor
-
N. Agafonova,
A. Aleksandrov,
O. Altinok,
A. Anokhina,
S Aoki,
A. Ariga,
T Ariga,
D. Autiero,
A. Badertscher,
A Bagulya, [......],
G Wilquet,
B. Wonsak,
V. Yakushev,
C S Yoon,
T Yoshioka,
J Yoshida,
Y. Zaitsev,
S. Zemskova,
A Zghiche,
R Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: The OPERA experiment is based on a hybrid technology combining electronic detectors and nuclear emulsions. OPERA collected muon-neutrino interactions during the 2008 and 2009 physics runs of the CNGS neutrino beam, produced at CERN with an energy range of about 5-35 GeV. A total of $5.3 \times 10^{19}$ protons on target equivalent luminosity has been analysed with the OPERA electronic detectors: scintillator strips target trackers and magnetic muon spectrometers equipped with resistive plate gas chambers and drift tubes, allowing a detailed reconstruction of muon-neutrino interactions. Charged Current (CC) and Neutral Current (NC) interactions are identified, using the measurements in the electronic detectors, and the NC/CC ratio is computed. The momentum distribution and the charge of the muon tracks produced in CC interactions are analysed. Calorimetric measurements of the visible energy are performed for both the CC and NC samples. For CC events the Bjorken-$y$ distribution and the hadronic shower profile are computed. The results are compared to a detailed Monte Carlo simulation of the electronic detectors' response.
New Journal of Physics 12/2012; 13:053051. · 4.18 Impact Factor
-
The OPERA Collaboration,
T. Adam,
N. Agafonova,
A. Aleksandrov,
A. Anokhina,
S. Aoki,
A. Ariga,
T. Ariga,
D. Autiero,
A. Badertscher, [......],
J. L. Vuilleumier,
G. Wilquet,
B. Wonsak,
J. Wurtz,
C. S. Yoon,
J. Yoshida,
Y. Zaitsev,
S. Zemskova,
A. Zghiche,
R. Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: In spring 2012 CERN provided two weeks of a short bunch proton beam dedicated
to the neutrino velocity measurement over a distance of 730 km. The OPERA
neutrino experiment at the underground Gran Sasso Laboratory used an upgraded
setup compared to the 2011 measurements, improving the measurement time
accuracy. An independent timing system based on the Resistive Plate Chambers
was exploited providing a time accuracy of $\sim$1 ns. Neutrino and
anti-neutrino contributions were separated using the information provided by
the OPERA magnetic spectrometers. The new analysis profited from the precision
geodesy measurements of the neutrino baseline and of the CNGS/LNGS clock
synchronization. The neutrino arrival time with respect to the one computed
assuming the speed of light in vacuum is found to be $\delta t_\nu \equiv TOF_c
- TOF_\nu= (0.6 \pm 0.4\ (stat.) \pm 3.0\ (syst.))$ ns and $\delta
t_{\bar{\nu}} \equiv TOF_c - TOF_{\bar{\nu}} = (1.7 \pm 1.4\ (stat.) \pm 3.1\
(syst.))$ ns for $\nu_{\mu}$ and $\bar{\nu}_{\mu}$, respectively. This
corresponds to a limit on the muon neutrino velocity with respect to the speed
of light of $-1.8 \times 10^{-6} < (v_{\nu}-c)/c < 2.3 \times 10^{-6}$ at 90%
C.L. This new measurement confirms with higher accuracy the revised OPERA
result.
12/2012;
-
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
C. Alexa,
V. Andreev,
S. Antonelli,
P. Antonioli,
A. Antonov, [......],
W. Zeuner,
Z. Zhang,
B. O. Zhautykov,
N. Zhmak,
A. Zichichi,
R. Žlebčík,
H. Zohrabyan,
Z. Zolkapli,
F. Zomer,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: Measurements of open charm production cross sections in deep-inelastic ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced
cross sections sigma_red^{c\bar{c}} for charm production are obtained in the
kinematic range of photon virtuality 2.5<Q2<2000 GeV2 and Bjorken scaling
variable 0.00003<x<0.05. The combination method accounts for the correlations
of the systematic uncertainties among the different data sets. The combined
charm data together with the combined inclusive deep-inelastic scattering cross
sections from HERA are used as input for a detailed NLO QCD analysis to study
the influence of different heavy flavour schemes on the parton distribution
functions. The optimal values of the charm mass as a parameter in these
different schemes are obtained. The implications on the NLO predictions for
W^{\pm} and Z production cross sections at the LHC are investigated. Using the
fixed flavour number scheme, the running mass of the charm quark is determined.
11/2012;
-
ZEUS collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
O. Zabiegalov,
A. F. Żarnecki,
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
A. Zichichi,
Z. Zolkapli,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: The production of Z0 bosons in the reaction ep -> eZ0p*, where p* stands for
a proton or a low-mass nucleon resonance, has been studied in ep collisions at
HERA using the ZEUS detector. The analysis is based on a data sample collected
between 1996 and 2007, amounting to 496 pb-1 of integrated luminosity. The Z0
was measured in the hadronic decay mode. The elasticity of the events was
ensured by a cut on eta_max < 3.0, where eta_max is the maximum pseudorapidity
of energy deposits in the calorimeter defined with respect to the proton beam
direction. A signal was observed at the Z0 mass. The cross section of the
reaction ep -> eZ0p* was measured to be sigma(ep -> eZ0p*) = 0.13 +/- 0.06
(stat.) +/- 0.01 (syst.) pb, in agreement with the Standard Model prediction of
0.16 pb. This is the first measurement of Z0 production in ep collisions.
10/2012;
-
ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
M. Zolko,
D. S. Zotkin
-
M. Antonello,
D. Bagliani,
B. Baibussinov,
H. Bilokon,
F. Boffelli,
M. Bonesini,
E. Calligarich,
N. Canci,
S. Centro,
A. Cesana, [......],
S. Simone,
M. Sioli,
G. Sirri,
M. Spurio,
L. Stanco,
A. Surdo,
M. Tenti,
V. Togo,
M. Ventura,
M. Zago
[show abstract]
[hide abstract]
ABSTRACT: A new experiment with an intense ~2 GeV neutrino beam at CERN SPS is proposed
in order to definitely clarify the possible existence of additional neutrino
states, as pointed out by neutrino calibration source experiments, reactor and
accelerator experiments and measure the corresponding oscillation parameters.
The experiment is based on two identical LAr-TPCs complemented by magnetized
spectrometers detecting electron and muon neutrino events at Far and Near
positions, 1600 m and 300 m from the proton target, respectively. The ICARUS
T600 detector, the largest LAr-TPC ever built with a size of about 600 ton of
imaging mass, now running in the LNGS underground laboratory, will be moved at
the CERN Far position. An additional 1/4 of the T600 detector (T150) will be
constructed and located in the Near position. Two large area spectrometers will
be placed downstream of the two LAr-TPC detectors to perform charge
identification and muon momentum measurements from sub-GeV to several GeV
energy range, greatly complementing the physics capabilities. This experiment
will offer remarkable discovery potentialities, collecting a very large number
of unbiased events both in the neutrino and antineutrino channels, largely
adequate to definitely settle the origin of the observed neutrino-related
anomalies.
08/2012;
-
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo,
O. Arslan, [......],
A. F. Żarnecki,
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: A search for first-generation leptoquarks was performed in electron-proton and positron-proton collisions recorded with the ZEUS detector at HERA in 2003–2007 using an integrated luminosity of 366 pb-1. Final states with an electron and jets or with missing transverse momentum and jets were analyzed, searching for resonances or other deviations from the standard model predictions. No evidence for any leptoquark signal was found. The data were combined with data previously taken at HERA, resulting in a total integrated luminosity of 498 pb-1. Limits on the Yukawa coupling, λ, of leptoquarks were set as a function of the leptoquark mass for different leptoquark types within the Buchmüller-Rückl-Wyler model. Leptoquarks with a coupling λ=0.3 are excluded for masses up to 699 GeV.
Phys. Rev. D. 07/2012; 86(1).
-
N. Yu. Agafonova,
P. Antonioli,
V. V. Ashikhmin,
G. Bari,
E. Bressan,
L. Evans,
M. Garbini,
P. Giusti,
A. S. Malguin,
R. Persiani, [......],
M. Spinetti,
L. Stanco,
M. Stipcevic,
M. Tenti,
F. Terranova,
V. Tioukov,
B. Wonsak,
V. Yakushev,
Y. Zaitsev,
S. Zemskova
[show abstract]
[hide abstract]
ABSTRACT: The purpose of this work is to report the measurement of a time-shift in the
OPERA set-up in a totally independent way from Time Of Flight (TOF)
measurements of CNGS neutrino events. The LVD and OPERA experiments are both
installed in the same laboratory: LNGS. The relative position of the two
detectors, separated by an average distance of ~ 160 m, allows the use of very
high energy horizontal muons to cross-calibrate the timing systems of the two
detectors, using a TOF technique which is totally independent from TOF of CNGS
neutrino events. Indeed, the OPERA-LVD direction lies along the so-called
"Teramo anomaly", a region in the Gran Sasso massif where LVD has established,
many years ago, the existence of an anomaly in the mountain structure, which
exhibits a low m. w. e. thickness for horizontal directions. The "abundant"
high-energy horizontal muons (nearly 100 per year) going through LVD and OPERA
exist because of this anomaly in the mountain orography. The total live time of
the data in coincidence correspond to 1200 days from mid 2007 until March 2012.
The time coincidence study of LVD and OPERA detectors is based on 306 cosmic
horizontal muon events and shows the existence of a negative time shift in the
OPERA set-up of the order of deltaT(AB) = - (73 \pm 9) ns when two calendar
periods, A and B, are compared. This result shows a systematic effect in the
OPERA timing system from August 2008 until December 2011. The size of the
effect is comparable with the neutrino velocity excess recently measured by
OPERA. It is probably interesting not to forget that with the MRPC technology
developed by the ALICE Bologna group the TOF world record accuracy of 20 ps was
reached. That technology can be implemented at LNGS for a high precision
determination of TOF with the CNGS neutrino beams of an order of magnitude
smaller than the value of the OPERA systematic effect.
06/2012;
-
ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
A. F. Zarnecki,
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
Z. Zolkapli,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: Inclusive-jet cross sections have been measured in the reaction ep->e+jet+X
for photon virtuality Q2 < 1 GeV2 and gamma-p centre-of-mass energies in the
region 142 < W(gamma-p) < 293 GeV with the ZEUS detector at HERA using an
integrated luminosity of 300 pb-1. Jets were identified using the kT, anti-kT
or SIScone jet algorithms in the laboratory frame. Single-differential cross
sections are presented as functions of the jet transverse energy, ETjet, and
pseudorapidity, etajet, for jets with ETjet > 17 GeV and -1 < etajet < 2.5. In
addition, measurements of double-differential inclusive-jet cross sections are
presented as functions of ETjet in different regions of etajet.
Next-to-leading-order QCD calculations give a good description of the
measurements, except for jets with low ETjet and high etajet. The influence of
non-perturbative effects not related to hadronisation was studied. Measurements
of the ratios of cross sections using different jet algorithms are also
presented; the measured ratios are well described by calculations including up
to O(alphas2) terms. Values of alphas(Mz) were extracted from the measurements
and the energy-scale dependence of the coupling was determined. The value of
alphas(Mz) extracted from the measurements based on the kT jet algorithm is
alphas(Mz) = 0.1206 +0.0023 -0.0022 (exp.) +0.0042 -0.0035 (th.); the results
from the anti-kT and SIScone algorithms are compatible with this value and have
a similar precision.
05/2012;
-
S. Chekanov,
M. Derrick,
S. Magill,
S. Miglioranzi,
B. Musgrave,
D. Nicholass,
J. Repond,
R. Yoshida,
M.C.K. Mattingly,
N. Pavel, [......],
S. Bhadra,
C.D. Catterall,
Y. Cui,
G. Hartner,
S. Menary,
U. Noor,
M. Soares,
J. Standage,
J. Whyte,
The ZEUS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: A search for stop production in R-parity-violating supersymmetry has been performed in e+p interactions with the ZEUS detector at HERA, using an integrated luminosity of 65pb-1. At HERA, the R-parity-violating coupling λ’ allows resonant squark production, e+d®[(q)\tilde]e^+d\to\tilde{q}. Since the lowest-mass squark state in most supersymmetry models is the light stop, [(t)\tilde]\tilde{t}, this search concentrated on production of [(t)\tilde]\tilde{t}, followed either by a direct R-parity-violating decay, or by the gauge decay to b[(c)\tilde]+1b\tilde{\chi}^+_{1}. No evidence for stop production was found and limits were set on λ’131 as a function of the stop mass in the framework of the minimal supersymmetric standard model. The results have also been
interpreted in terms of constraints on the parameters of the minimal supergravity model.
European Physical Journal C 04/2012; 50(2):269-281. · 3.63 Impact Factor
-
The ZEUS collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin,
Z. Zulkapli
[show abstract]
[hide abstract]
ABSTRACT: Measurements of the cross sections for charged current deep inelastic scattering in e
+
p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with
an integrated luminosity of 132pb−1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318GeV. The total cross section is presented at positive
and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ
2, dσ/dx and dσ/dy are presented for Q
2>200GeV2. The reduced cross-section [(s)\tilde]\tilde{\sigma} is presented in the kinematic range 200<Q
2<60 000GeV2 and 0.006<x<0.562. The measurements agree well with the predictions of the Standard Model. The results are used to determine a lower
limit on the mass of a hypothetical right-handed W boson.
European Physical Journal C 04/2012; 70(4):945-963. · 3.63 Impact Factor
-
ZEUS Collaboration,
S. Chekanov,
M. Derrick,
S. Magill,
B. Musgrave,
D. Nicholass,
J. Repond,
R. Yoshida,
M. C. K. Mattingly,
P. Antonioli, [......],
E. Brownson,
D. D. Reeder,
A. A. Savin,
W. H. Smith,
H. Wolfe,
S. Bhadra,
C. D. Catterall,
G. Hartner,
U. Noor,
J. Whyte
[show abstract]
[hide abstract]
ABSTRACT: The proton-dissociative diffractive photoproduction of J/ψ mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb−1. The cross section is presented as a function of the photon-proton centre-of-mass energy and of the squared four-momentum
transfer at the proton vertex. The results are compared to perturbative QCD calculations.
KeywordsLepton-Nucleon Scattering
Journal of High Energy Physics 04/2012; 2010(5):1-36. · 5.83 Impact Factor
-
The ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin,
Z. Zulkapli
[show abstract]
[hide abstract]
ABSTRACT: Beauty production in deep inelastic scattering with events in which a muon and a jet are observed in the final state has been
measured with the ZEUS detector at HERA using an integrated luminosity of 114pb−1. The fraction of events with beauty quarks in the data was determined using the distribution of the transverse momentum of
the muon relative to the jet. The cross section for beauty production was measured in the kinematic range of photon virtuality,
Q
2>2GeV2, and inelasticity, 0.05<y<0.7, with the requirement of a muon and a jet. Total and differential cross sections are presented and compared to QCD predictions.
The beauty contribution to the structure function F
2 was extracted and is compared to theoretical predictions.
European Physical Journal C 04/2012; 69(3):347-360. · 3.63 Impact Factor
-
ZEUS collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin,
Z. Zulkapli
[show abstract]
[hide abstract]
ABSTRACT: Charm production in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity
of 120 pb−1. The hadronic decay channels D
+ → K
S
0
π
+, Λ
c
+ → pK
S
0 and Λ
c
+ → Λπ
+, and their charge conjugates, were reconstructed. The presence of a neutral strange hadron in the final state reduces the
combinatorial background and extends the measured sensitivity into the low transverse momentum region. The kinematic range
is 0 < p
T
(D
+, Λ
c
+) < 10 GeV, |η(D
+, Λ
c
+)| < 1.6, 1.5 < Q
2 < 1000 GeV2 and 0.02 < y < 0.7. Inclusive and differential cross sections for the production of D
+ mesons are compared to next-to-leading-order QCD predictions. The fraction of c quarks hadronising into Λ
c
+ baryons is extracted.
KeywordsLepton-Nucleon Scattering
Journal of High Energy Physics 04/2012; 2010(11):1-27. · 5.83 Impact Factor
-
The ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin,
Z. Zulkapli
[show abstract]
[hide abstract]
ABSTRACT: Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374pb−1. The measurement was performed at large values of the photon virtuality, Q
2, between 125 and 20 000GeV2. The jets were reconstructed with the k
T
cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, EjetT,BE^{\rm jet}_{T,{\rm B}}, to be larger than 8GeV. In addition, the invariant mass of the dijet system, MjjM_{\rm jj}, was required to be greater than 20GeV. The cross sections are described by the predictions of next-to-leading-order QCD.
European Physical Journal C 04/2012; 70(4):965-982. · 3.63 Impact Factor
-
The ZEUS Collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
R. Aggarwal,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo, [......],
L. Zawiejski,
O. Zenaiev,
W. Zeuner,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin,
Z. Zulkapli
[show abstract]
[hide abstract]
ABSTRACT: The production of beauty quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared Q
2>10GeV2, using an integrated luminosity of 363 pb−1. The beauty events were identified using electrons from semileptonic b decays with a transverse momentum 0.9 < pTe < 80.9 < p_{T}^{e} < 8GeV and pseudorapidity |η
e
|<1.5. Cross sections for beauty production were measured and compared with next-to-leading-order QCD calculations. The beauty
contribution to the proton structure function F
2 was extracted from the double-differential cross section as a function of Bjorken-x and Q
2.
European Physical Journal C 04/2012; 71(2):1-15. · 3.63 Impact Factor
-
and ZEUS collaborations,
F. D. Aaron,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
M. Al-daya Martin,
C. Alexa,
V. Andreev,
S. Antonelli, [......],
Z. Zhang,
B. O. Zhautykov,
A. Zhokin,
C. Zhou,
A. Zichichi,
T. Zimmermann,
H. Zohrabyan,
M. Zolko,
F. Zomer,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral
and charged current unpolarised e
±
p scattering at HERA during the period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer
squared, Q
2, and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy.
The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0,
with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the
fit result.
Journal of High Energy Physics 04/2012; 2010(1):1-63. · 5.83 Impact Factor
-
ZEUS collaboration,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
S. Antonelli,
P. Antonioli,
A. Antonov,
M. Arneodo,
V. Aushev, [......],
R. Yoshida,
C. Youngman,
A. F. Żarnecki,
O. Zenaiev,
B. O. Zhautykov,
N. Zhmak,
C. Zhou,
A. Zichichi,
M. Zolko,
D. S. Zotkin
[show abstract]
[hide abstract]
ABSTRACT: Charged particle production has been studied in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 0.44 fb−1. Distributions of scaled momenta in the Breit frame are presented for particles in the current fragmentation region. The
evolution of these spectra with the photon virtuality, Q
2, is described in the kinematic region 10 < Q
2 < 41000Ge V2. Next-to-leading-order and modified leading-log-approximation QCD calculations as well as predictions from Monte Carlo models
are compared to the data. The results are also compared to e
+
e
− annihilation data. The dependences of the pseudorapidity distribution of the particles on Q
2 and on the energy in the γp system, W, are presented and interpreted in the context of the hypothesis of limiting fragmentation.
KeywordsLepton-Nucleon Scattering
Journal of High Energy Physics 04/2012; 2010(6):1-42. · 5.83 Impact Factor
-
The and ZEUS collaborations,
F. D. Aaron,
H. Abramowicz,
I. Abt,
L. Adamczyk,
M. Adamus,
M. Aldaya Martin,
C. Alexa,
V. Andreev,
S. Antonelli, [......],
B. O. Zhautykov,
A. Zhokin,
C. Zhou,
A. Zichichi,
T. Zimmermann,
H. Zohrabyan,
M. Zolko,
F. Zomer,
D. S. Zotkin,
R. Zus
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ABSTRACT: A search for events containing an isolated electron or muon and missing transverse momentum produced in e
±
p collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 1994–2007 and correspond
to an integrated luminosity of 0.98 fb−1. The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single
W production. In the e
+
p data, at large hadronic transverse momentum P
T
X
> 25GeV, a total of 23 events are observed compared to a prediction of 14.0 ± 1.9. The total single W boson production cross section is measured as 1.06 ± 0.16 (stat.) ± 0.07 (sys.) pb, in agreement with an Standard Model (SM)
expectation of 1.26 ± 0.19 pb.
KeywordsLepton-Nucleon Scattering
Journal of High Energy Physics 04/2012; 2010(3):1-19. · 5.83 Impact Factor
