-
M. Antonello,
B. Baibussinov,
P. Benetti,
E. Calligarich,
N. Canci,
S. Centro,
A. Cesana,
K. Cieslik,
D. B. Cline,
A. G. Cocco, [......],
R. Sulej,
M. Szarska,
M. Terrani,
F. Varanini, S. Ventura,
C. Vignoli,
H. Wang,
X. Yang,
A. Zalewska,
K. Zaremba
[show abstract]
[hide abstract]
ABSTRACT: Liquid Argon Time Projection Chamber (LAr TPC) detectors offer charged
particle imaging capability with remarkable spatial resolution. Precise event
reconstruction procedures are critical in order to fully exploit the potential
of this technology. In this paper we present a new, general approach of
three-dimensional reconstruction for the LAr TPC with a practical application
to track reconstruction. The efficiency of the method is evaluated on a sample
of simulated tracks. We present also the application of the method to the
analysis of real data tracks collected during the ICARUS T600 detector
operation with the CNGS neutrino beam.
Advances in High Energy Physics 03/2013; 2013. · 4.52 Impact Factor
-
M. Antonello,
B. Baibussinov,
P. Benetti,
E. Calligarich,
N. Canci,
S. Centro,
A. Cesana,
K. Cieslik,
D. B. Cline,
A. G. Cocco, [......],
R. Sulej,
M. Szarska,
M. Terrani,
F. Varanini, S. Ventura,
C. Vignoli,
H. Wang,
X. Yang,
A. Zalewska,
K. Zaremba
[show abstract]
[hide abstract]
ABSTRACT: We report an early result from the ICARUS experiment on the search for nu_mu
to nu_e signal due to the LSND anomaly. The search was performed with the
ICARUS T600 detector located at the Gran Sasso Laboratory, receiving CNGS
neutrinos from CERN at an average energy of about 20 GeV, after a flight path
of about 730 km. The LSND anomaly would manifest as an excess of nu_e events,
characterized by a fast energy oscillation averaging approximately to
sin^2(1.27 Dm^2_new L/ E_nu) = 1/2. The present analysis is based on 1091
neutrino events, which are about 50% of the ICARUS data collected in 2010-2011.
Two clear nu_e events have been found, compared with the expectation of 3.7 +/-
0.6 events from conventional sources. Within the range of our observations,
this result is compatible with the absence of a LSND anomaly. At 90% and 99%
confidence levels the limits of 3.4 and 7.3 events corresponding to oscillation
probabilities of 5.4 10^-3 and 1.1 10^-2 are set respectively. The result
strongly limits the window of open options for the LSND anomaly to a narrow
region around (Dm^2, sin^2(2 theta))_new = (0.5 eV^2, 0.005), where there is an
overall agreement (90% CL) between the present ICARUS limit, the published
limits of KARMEN and the published positive signals of LSND and MiniBooNE
Collaborations.
European Physical Journal C 03/2013; 73:2345. · 3.63 Impact Factor
-
D. Abbaneo,
G. Abbiendi,
M. Abbrescia,
S. Abdullin,
A. Abdulsalam,
B.S. Acharya,
D. Acosta,
J.G. Acosta,
A. Adair,
W. Adam, [......],
M.H. Zoeller,
O. Zorba,
P. Zotto,
W. Zou,
G. Zumerle,
M. Zupan,
A. Zuranski,
R. Zuyeuski,
M. Zvada,
P. Zych
[show abstract]
[hide abstract]
ABSTRACT: The Higgs boson was postulated nearly five decades ago within the framework of the standard model of particle physics and
has been the subject of numerous searches at accelerators around the world. Its discovery would verify the existence of a
complex scalar field thought to give mass to three of the carriers of the electroweak force—the W+, W–, and Z0 bosons—as well as to the fundamental quarks and leptons. The CMS Collaboration has observed, with a statistical significance
of five standard deviations, a new particle produced in proton-proton collisions at the Large Hadron Collider at CERN. The
evidence is strongest in the diphoton and four-lepton (electrons and/or muons) final states, which provide the best mass resolution
in the CMS detector. The probability of the observed signal being due to a random fluctuation of the background is about 1
in 3 × 106. The new particle is a boson with spin not equal to 1 and has a mass of about 1.25 giga–electron volts. Although its measured
properties are, within the uncertainties of the present data, consistent with those expected of the Higgs boson, more data
are needed to elucidate the precise nature of the new particle.
Science 12/2012; 338(6114):1569-1575. · 31.20 Impact Factor
-
M. Antonello,
B. Baibussinov,
F. Boffelli,
P. Benetti,
E. Calligarich,
N. Canci,
S. Centro,
A. Cesana,
K. Cieslik,
D. B. Cline, [......],
R. Barzaghi,
B. Betti,
C. De Gaetani,
J. D. González Cobas,
D. Passoni,
L. Pinto,
J. Serrano,
P. Spinnato,
M. G. Visconti,
T. Wlostowski
[show abstract]
[hide abstract]
ABSTRACT: During May 2012, the CERN-CNGS neutrino beam has been operated for two weeks
for a total of 1.8 10^17 pot in bunched mode, with a 3 ns narrow width proton
beam bunches, separated by 100 ns. This tightly bunched beam structure allows a
very accurate time of flight measurement of neutrinos from CERN to LNGS on an
event-by-event basis. Both the ICARUS-T600 PMT-DAQ and the CERN-LNGS timing
synchronization have been substantially improved for this campaign, taking
ad-vantage of additional independent GPS receivers, both at CERN and LNGS as
well as of the deployment of the "White Rabbit" protocol both at CERN and LNGS.
The ICARUS-T600 detector has collected 25 beam-associated events; the
corresponding time of flight has been accurately evaluated, using all different
time synchronization paths. The measured neutrino time of flight is compatible
with the arrival of all events with speed equivalent to the one of light: the
difference between the expected value based on the speed of light and the
measured value is tof_c - tof_nu = (0.10 \pm 0.67stat. \pm 2.39syst.) ns. This
result is in agreement with the value previously reported by the ICARUS
collaboration, tof_c - tof_nu = (0.3 \pm 4.9stat. \pm 9.0syst.) ns, but with
improved statistical and systematic errors.
08/2012;
-
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;
-
The CMS collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
J. Leonard,
R. Loveless,
A. Mohapatra,
F. Palmonari,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: The first measurement of inclusive Z → τ
+
τ
− production in pp collisions at the LHC is presented, in the final states μ + hadrons, e + hadrons, e + μ, and μ + μ. The data sample corresponds to an integrated luminosity of 36 pb−1 collected with the CMS detector. The measured cross section is σ (pp → ZX) × B (Z → τ
+
τ
−) = 1.00 ± 0.05(stat.) ± 0.08(syst.) ± 0.04(lumi.)nb, which is in good agreement with the next-to-next-to-leading order QCD prediction and improves on previous measurements
in the Z → e+e− and μ
+
μ
− channels. The reconstruction efficiency for hadronic τ decays is determined with a precision of 7%.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2011(8):1-32. · 5.83 Impact Factor
-
The CMS collaboration,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
D. Lomidze,
R. Loveless,
A. Mohapatra,
W. Parker,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Measurements of primary charged hadron multiplicity distributions are presented for non-single-diffractive events in proton-proton
collisions at centre-of-mass energies of Ös = 0.9 \sqrt {s} = 0.9 , 2.36, and 7 TeV, in five pseudorapidity ranges from |η| < 0.5 to |η| < 2.4. The data were collected with the minimum-bias trigger of the CMS experiment during the LHC commissioning runs in 2009 and
the 7 TeV run in 2010. The multiplicity distribution at
Ös = 0.9\textTeV \sqrt {s} = 0.9\;{\text{TeV}} is in agreement with previous measurements. At higher energies the increase of the mean multiplicity with Ös \sqrt {s} is underestimated by most event generators. The average transverse momentum as a function of the multiplicity is also presented.
The measurement of higher-order moments of the multiplicity distribution confirms the violation of Koba-Nielsen-Olesen scaling
that has been observed at lower energies.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2011(1):1-38. · 5.83 Impact Factor
-
The CMS Collaboration,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
J. Leonard,
D. Lomidze,
R. Loveless,
A. Mohapatra,
G. Polese,
D. Reeder,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the underlying activity in scattering processes with p
T
scale in the GeV region is performed in proton–proton collisions at Ös = 0.9\sqrt{s} = 0.9TeV, using data collected by the CMS experiment at the LHC. Charged particle production is studied with reference to the
direction of a leading object, either a charged particle or a set of charged particles forming a jet. Predictions of several
QCD-inspired models as implemented in PYTHIA are compared, after full detector simulation, to the data. The models generally
predict too little production of charged particles with pseudorapidity |η|<2, p
T
>0.5 GeV/c, and azimuthal direction transverse to that of the leading object.
European Physical Journal C 04/2012; 70(3):555-572. · 3.63 Impact Factor
-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: First measurements of the W → ℓν and Z/γ
*
→ ℓℓ (ℓ = e, μ) production cross sections in proton-proton collisions at
Ös = 7\textTeV \sqrt {s} = 7\;{\text{TeV}} are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W → ℓν and 179 Z/γ
* → ℓℓ candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb. The measured
total W and Z/γ
∗-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels
are
sW\texttot \sigma_W^{\text{tot}} . BR(W → ℓν) = 9.96 ± 0.23(stat) ± 0.50(syst) ± 1.10(lumi) nb and
sZ /
g \texttot \sigma_{{{Z} \left/ {\gamma } \right.}}^{\text{tot}} BR(Z/γ
∗ → ℓℓ) = 0.82 ± 0.06 (stat) ± 0.05 (syst) ± 0.09(lumi) nb (within the invariant mass window 66 < m
ℓℓ
< 116GeV). The W/Z cross-section ratio is measured to be 11.7 ± 0.9(stat) ± 0.4(syst). In addition, measurements of the W
+ and W
− production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations
are found to agree with the measurements.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2010(12):1-65. · 5.83 Impact Factor
-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi,
L. Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the production cross-section for top quark pairs (t[`(t)]t\bar{t}) in pp collisions at Ös=7TeV\sqrt{s}=7\ \ \mbox{TeV} is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different
topologies: single lepton (electron e or muon μ) with large missing transverse energy and at least four jets, and dilepton (ee, μμ or eμ) with large missing transverse energy and at least two jets. In a data sample of 2.9pb−1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding
expected backgrounds from non-t[`(t)]t\bar{t} Standard Model processes are estimated using data-driven methods and determined to be 12.2±3.9 events and 2.5±0.6 events,
respectively. The kinematic properties of the selected events are consistent with SM t[`(t)]t\bar{t} production. The inclusive top quark pair production cross-section is measured to be
st[`(t)]=145±31(stat.) +42-27(syst.)pb.\sigma_{t\bar{t}}=145\pm31(\mathrm{stat.}) {}^{+42}_{-27}(\mathrm {syst.})\ \mbox{pb}.
The measurement agrees with perturbative QCD calculations.
European Physical Journal C 04/2012; 71(3):1-36. · 3.63 Impact Factor
-
The CMS Collaboration,
S. Chatrchyan,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan, [......],
J. Leonard,
R. Loveless,
A. Mohapatra,
F. Palmonari,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: A search for supersymmetry is presented using a sample of events with b jets and missing transverse momentum. The search uses
a data sample of proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of
35 pb−1, collected with the CMS detector. A total of 0.33 - 0.33 + 0.43 0.33_{ - 0.33}^{ + 0.43} (stat.) ± 0.13 (syst.) events is predicted, using control samples in the data, to arise from standard model processes, and one event is observed
in the data. Upper limits are set at the 95% confidence level on the cross sections of benchmark supersymmetric models.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2011(7):1-26. · 5.83 Impact Factor
-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: Jet cross sections have been measured for the first time in proton-proton collisions at a centre-of-mass energy of 7TeV using
the ATLAS detector. The measurement uses an integrated luminosity of 17nb−1 recorded at the Large Hadron Collider. The anti-k
t
algorithm is used to identify jets, with two jet resolution parameters, R=0.4 and 0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets
above 60GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse
momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and the angular variableχ. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation
of the theory in a new kinematic regime.
European Physical Journal C 04/2012; 71(2):1-59. · 3.63 Impact Factor
-
The CMS collaboration,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
D. Lomidze,
R. Loveless,
A. Mohapatra,
W. Parker,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Measurements of inclusive W and Z boson production cross sections in pp collisions at Ös = 7 \sqrt {s} = 7 TeV are presented, based on 2.9 pb−1 of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are
combined to give
s( \textpp ® \textWX ) B( \textW ® ln ) = 9.95±0.07( \textstat. )±0.28( \textsyst. )±1.09 \sigma \left( {{\text{pp}} \to {\text{W}}X} \right) \times \mathcal{B}\left( {{\text{W}} \to \ell \nu } \right) = 9.95\pm 0.07\left( {{\text{stat}}{.}} \right)\pm 0.28\left( {{\text{syst}}{.}} \right)\pm 1.09 (lumi.) nb and
s( \textpp ® \textZX ) B( Z ® l+ l- ) = 0.931±0.026( \textstat. )±0.023( \textsyst. )±0.102 \sigma \left( {{\text{pp}} \to {\text{Z}}X} \right) \times \mathcal{B}\left( {Z \to {\ell^{+} }{\ell^{-} }} \right) = 0.931\pm 0.026\left( {{\text{stat}}{.}} \right)\pm 0.023\left( {{\text{syst}}{.}} \right)\pm 0.102 (lumi.) nb, where ℓ stands for either e or μ. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recent parton distribution functions,
are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty
of less than 4%, are also reported.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2011(1):1-40. · 5.83 Impact Factor
-
The CMS collaboration,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
C. Fabjan,
M. Friedl, [......],
J. Leonard,
D. Lomidze,
R. Loveless,
A. Mohapatra,
D. Reeder,
I. Ross,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: The result of a search at the LHC for heavy stable charged particles produced in pp collisions at
Ös = 7\textTeV \sqrt {s} = 7\;{\text{TeV}} is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with
heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same
signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c
2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon
detectors. A lower limit of 311 GeV/c
2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this
particle becomes neutral before reaching the muon detectors.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2011(3):1-29. · 5.83 Impact Factor
-
CMS Collaboration,
V. Khachatryan,
A. M. Sirunyan,
A. Tumasyan,
W. Adam,
T. Bergauer,
M. Dragicevic,
J. Erö,
M. Friedl,
R. Frühwirth, [......],
C. Lazaridis,
J. Leonard,
D. Lomidze,
R. Loveless,
A. Mohapatra,
D. Reeder,
A. Savin,
W. H. Smith,
J. Swanson,
M. Weinberg
[show abstract]
[hide abstract]
ABSTRACT: Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton
collisions at Ös = 0.9\sqrt{s} = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive
interactions, the average charged-hadron transverse momentum is measured to be 0.46 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 ± 0.01 (stat.) ± 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between --2.4 and +2.4. At these energies, the measured pseudorapidity densities in the
central region, dN
ch/dη||η|<0.5, are 3:48 ± 0:02 (stat.) ± 0.13 (syst.) and 4:47 ± 0:04 (stat.) ± 0.16 (syst.), respectively. The results at 0.9 TeV
are in agreement with previous measurements and confirm the expectation of near equal hadron production in [`(p)] p \overline p p and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2010(2):1-35. · 5.83 Impact Factor
-
The ATLAS collaboration,
G. Aad,
E. Abat,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins, [......],
M. Ziolkowski,
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi
[show abstract]
[hide abstract]
ABSTRACT: More than half a million minimum-bias events of LHC collision data were collected by the ATLAS experiment in December 2009
at centre-of-mass energies of 0.9 TeV and 2.36 TeV. This paper reports on studies of the initial performance of the ATLAS
detector from these data. Comparisons between data and Monte Carlo predictions are shown for distributions of several track-and
calorimeter-based quantities. The good performance of the ATLAS detector in these first data gives confidence for successful
running at higher energies.
KeywordsHadron-Hadron Scattering
Journal of High Energy Physics 04/2012; 2010(9):1-66. · 5.83 Impact Factor
-
The ATLAS Collaboration,
G. Aad,
B. Abbott,
J. Abdallah,
A. A. Abdelalim,
A. Abdesselam,
O. Abdinov,
B. Abi,
M. Abolins,
H. Abramowicz, [......],
R. Zitoun,
L. Živković,
V. V. Zmouchko,
G. Zobernig,
A. Zoccoli,
Y. Zolnierowski,
A. Zsenei,
M. zur Nedden,
V. Zutshi,
L. Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at Ös = 7\sqrt{s} = 7TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having
different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from
these methods are monitored as a function of time and of μ, the average number of inelastic interactions per bunch crossing. Residual time- and μ-dependence between the methods is less than 2% for 0<μ<2.5. Absolute luminosity calibrations, performed using beam separation scans, have a common systematic uncertainty of ±11%,
dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods
differ by at most ±2%. The visible cross sections measured using the beam scans are compared to predictions obtained with
the PYTHIA and PHOJET event generators and the ATLAS detector simulation.
European Physical Journal C 04/2012; 71(4):1-37. · 3.63 Impact Factor
-
M. Antonello,
P. Aprili,
B. Baibussinov,
M. Baldo Ceolin,
P. Benetti,
E. Calligarich,
N. Canci,
F. Carbonara,
S. Centro,
A. Cesana, [......],
M. Terrani,
F. Varanini, S. Ventura,
C. Vignoli,
H. Wang,
X. Yang,
A. Zalewska,
K. Zaremba,
P. Alvarez Sanchez,
J. Serrano
[show abstract]
[hide abstract]
ABSTRACT: The CERN-SPS accelerator has been briefly operated in a new, lower intensity
neutrino mode with ~10^12 p.o.t. /pulse and with a beam structure made of four
LHC-like extractions, each with a narrow width of 3 ns, separated by 524 ns.
This very tightly bunched beam structure represents a substantial progress with
respect to the ordinary operation of the CNGS beam, since it allows a very
accurate time-of-flight measurement of neutrinos from CERN to LNGS on an
event-to-event basis. The ICARUS T600 detector has collected 7 beam-associated
events, consistent with the CNGS delivered neutrino flux of 2.2 10^16 p.o.t.
and in agreement with the well known characteristics of neutrino events in the
LAr-TPC. The time of flight difference between the speed of light and the
arriving neutrino LAr-TPC events has been analysed. The result is compatible
with the simultaneous arrival of all events with equal speed, the one of light.
This is in a striking difference with the reported result of OPERA that claimed
that high energy neutrinos from CERN should arrive at LNGS about 60 ns earlier
than expected from luminal speed.
03/2012;
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R Acciarri,
M Antonello,
F Boffelli,
M Cambiaghi,
N Canci,
F Cavanna,
A G Cocco,
N Deniskina,
F Di Pompeo,
G Fiorillo, [......],
G B Piano Mortari,
F Pietropaolo,
G L Raselli,
C Rubbia,
E Segreto,
A M Szelc,
A Triossi, S Ventura,
C Vignoli,
A Zani
[show abstract]
[hide abstract]
ABSTRACT: Liquified noble gases are widely used as a target in direct Dark Matter searches. Signals from scintillation in the liquid, following energy deposition from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should be recorded down to very low energies by photosensors suitably designed to operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter searches currently implement photomultiplier tubes for signal read-out. In the last few years PMTs with photocathodes operating down to liquid Argon temperatures (87 K) have been specially developed with increasing Quantum Efficiency characteristics. The most recent of these, Hamamatsu Photonics K.K. Mod. R11065 with peak QE up to about 35%, has been extensively tested within the R&D program of the WArP Collaboration. During these tests the Hamamatsu PMTs showed excellent performance and allowed obtaining a light yield around 7 phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12% range, sufficient for detection of events down to few keVee of energy deposition. This shows that this new type of PMT is suited for experimental applications, in particular for new direct Dark Matter searches with LAr-based experiments.
Journal of Instrumentation 01/2012; 7(01):P01016. · 1.87 Impact Factor
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ICARUS Collaboration,
M. Antonello,
P. Aprili,
B. Baibussinov,
M. Baldo Ceolin,
P. Benetti,
E. Calligarich,
N. Canci,
F. Carbonara,
S. Centro, [......],
R. Sulej,
M. Szarska,
M. Terrani,
F. Varanini, S. Ventura,
C. Vignoli,
H. Wang,
X. Yang,
A. Zalewska,
K. Zaremba
[show abstract]
[hide abstract]
ABSTRACT: The OPERA collaboration has claimed evidence of superluminal {\nu}{_\mu}
propagation between CERN and the LNGS. Cohen and Glashow argued that such
neutrinos should lose energy by producing photons and e+e- pairs, through Z0
mediated processes analogous to Cherenkov radiation. In terms of the parameter
delta=(v^2_nu-v^2_c)/v^2_c, the OPERA result implies delta = 5 x 10^-5. For
this value of \delta a very significant deformation of the neutrino energy
spectrum and an abundant production of photons and e+e- pairs should be
observed at LNGS. We present an analysis based on the 2010 and part of the 2011
data sets from the ICARUS experiment, located at Gran Sasso National Laboratory
and using the same neutrino beam from CERN. We find that the rates and
deposited energy distributions of neutrino events in ICARUS agree with the
expectations for an unperturbed spectrum of the CERN neutrino beam. Our results
therefore refute a superluminal interpretation of the OPERA result according to
the Cohen and Glashow prediction for a weak current analog to Cherenkov
radiation. In particular no superluminal Cherenkov like e+e- pair or gamma
emission event has been directly observed inside the fiducial volume of the
"bubble chamber like" ICARUS TPC-LAr detector, setting the much stricter limit
of delta < 2.5 10^-8 at the 90% confidence level, comparable with the one due
to the observations from the SN1987A.
10/2011;
