-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
G. K. Mallot,
A. Mann,
C. Marchand,
A. Martin,
J. Marzec,
T. Matsuda,
G. Meshcheryakov,
W. Meyer,
T. Michigami,
Yu. V. Mikhailov
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
M. Wilfert,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The gluon polarisation in the nucleon was measured using open charm
production by scattering 160 GeV/c polarised muons off longitudinally polarised
protons or deuterons. The data were taken by the COMPASS collaboration between
2002 and 2007. A detailed account is given of the analysis method that includes
the application of neural networks. Several decay channels of D^0 mesons are
investigated. Longitudinal spin asymmetries of the D meson production
cross-sections are extracted in bins of D^0 transverse momentum and energy. At
leading order QCD accuracy the average gluon polarisation is determined as
(Delta g/G)^LO=-0.06 +/- 0.21 (stat.) +/- 0.08 (syst.) at the scale <mu^2> ~13
(GeV/c)^2 and an average gluon momentum fraction ~ 0.11. For the first time,
the average gluon polarisation is also obtained at next-to-leading order QCD
accuracy as (Delta g/G)^NLO = -0.13 +/- 0.15 (stat.) +/- 0.15 (syst.) at the
scale <mu^2> ~ 13 (\GeV/c)^2 and ~ 0.20.
11/2012;
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
M. Wilfert,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The production of D* and D mesons in inelastic scattering of 160 GeV/c muons
off a ^6LiD target has been investigated with the COMPASS spectrometer at CERN
for 0.003 (GeV/c)^2 < Q^2 < 10 (GeV/c)^2 and 3x10^-5< x_Bj < 0.1. The study is
based on 8100 events where a D^0 or anti D^0 is detected subsequently to a D*+
or D*- decay, and on 34000 events, where only a D^0 or anti D^0 is detected.
Kinematic distributions of D*, D and K*_2 are given as a function of their
energy E, transverse momentum p_T, energy fraction z, and of the virtual photon
variables nu, Q^2 and x_Bj. Semi-inclusive differential D* production
cross-sections are compared with theoretical predictions for D* production via
photon-gluon fusion into open charm. The total observed production
cross-section for D*+/- mesons with laboratory energies between 22 and 86 GeV
is 1.9 nb. Significant cross-section asymmetries are observed between D*+ and
D*- production for nu<40 GeV and z>0.6.
European Physical Journal C 11/2012; 72(12). · 3.63 Impact Factor
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badełek,
F. Balestra, [......],
M. Wilfert,
R. Windmolders,
W. Wiślicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The transverse target spin azimuthal asymmetry A_UT in hard exclusive
production of rho^0 mesons was measured at COMPASS by scattering 160 GeV/c
muons off transversely polarised protons and deuterons. The measured asymmetry
is sensitive to the nucleon helicity-flip generalised parton distributions E^q,
which are related to the orbital angular momentum of quarks in the nucleon. The
Q^2, x_B and p_t^2 dependence of A_UT is presented in a wide kinematic range.
Results for deuterons are obtained for the first time. The measured asymmetry
is small in the whole kinematic range for both protons and deuterons, which is
consistent with the theoretical interpretation that contributions from GPDs E^u
and E^d approximately cancel.
07/2012;
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badełek,
F. Balestra, [......],
L. Wang,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The cross section for production of charged hadrons with high transverse
momenta in scattering of 160 GeV/c muons off nucleons at low photon
virtualities has been measured at the COMPASS experiment at CERN. The results,
which cover transverse momenta from 1.1 to 3.6 GeV/c, are compared to a
next-to-leading order perturbative Quantum Chromodynamics (NLO pQCD)
calculation in order to evaluate the applicability of pQCD to this process in
the kinematic domain of the experiment. The shape of the calculated
differential cross section as a function of transverse momentum is found to be
in good agreement with the experimental data, but the normalization is
underestimated by NLO pQCD. This discrepancy may point towards the relevance of
terms beyond NLO in the pQCD framework. The dependence of the cross section on
the pseudo-rapidity and on the charge of the hadrons is also discussed.
07/2012;
-
N. Abgrall,
A. Aduszkiewicz,
T. Anticic,
N. Antoniou,
J. Argyriades,
B. Baatar,
A. Blondel,
J. Blumer,
M. Bogomilov,
A. Bravar, [......],
M. Hartz,
A. K. Ichikawa,
H. Kubo,
A. D. Marino,
K. Matsuoka,
A. Murakami,
T. Nakaya,
K. Suzuki,
T. Yuan,
E. D. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The T2K long-baseline neutrino oscillation experiment in Japan needs precise
predictions of the initial neutrino flux. The highest precision can be reached
based on detailed measurements of hadron emission from the same target as used
by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The
corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at
the CERN SPS using a replica of the T2K graphite target. In this paper details
of the experiment, data taking, data analysis method and results from the 2007
pilot run are presented. Furthermore, the application of the NA61/SHINE
measurements to the predictions of the T2K initial neutrino flux is described
and discussed.
07/2012;
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
M. Wilfert,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The COMPASS Collaboration at CERN has measured the transverse spin azimuthal
asymmetry of charged hadrons produced in semi-inclusive deep inelastic
scattering using a 160 GeV positive muon beam and a transversely polarised NH_3
target. The Collins asymmetry of the proton was extracted in the Bjorken x
range 0.003<x<0.7. These new measurements confirm with higher accuracy previous
measurements from the COMPASS and HERMES collaborations, which exhibit a
definite effect in the valence quark region. The asymmetries for negative and
positive hadrons are similar in magnitude and opposite in sign. They are
compatible with model calculations in which the u-quark transversity is
opposite in sign and somewhat larger than the d-quark transversity distribution
function. The asymmetry is extracted as a function of Bjorken $x$, the relative
hadron energy $z$ and the hadron transverse momentum p_T^h. The high statistics
and quality of the data also allow for more detailed investigations of the
dependence on the kinematic variables. These studies confirm the leading-twist
nature of the Collins asymmetry.
05/2012;
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
M. Wilfert,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The COMPASS Collaboration at CERN has measured the transverse spin azimuthal
asymmetry of charged hadrons produced in semi-inclusive deep inelastic
scattering using a 160 GeV positive muon beam and a transversely polarised NH_3
target. The Sivers asymmetry of the proton has been extracted in the Bjorken x
range 0.003<x<0.7. The new measurements have small statistical and systematic
uncertainties of a few percent and confirm with considerably better accuracy
the previous COMPASS measurement. The Sivers asymmetry is found to be
compatible with zero for negative hadrons and positive for positive hadrons, a
clear indication of a spin-orbit coupling of quarks in a transversely polarised
proton. As compared to measurements at lower energy, a smaller Sivers asymmetry
for positive hadrons is found in the region x > 0.03. The asymmetry is
different from zero and positive also in the low x region, where sea-quarks
dominate. The kinematic dependence of the asymmetry has also been investigated
and results are given for various intervals of hadron and virtual photon
fractional energy. In contrast to the case of the Collins asymmetry, the
results on the Sivers asymmetry suggest a strong dependence on the
four-momentum transfer to the nucleon, in agreement with the most recent
calculations.
05/2012;
-
M. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. Austregesilo,
B. Badełek,
F. Balestra,
J. Ball,
J. Barth, [......],
Q. Weitzel,
R. Windmolders,
W. Wiślicki,
H. Wollny,
K. Zaremba,
E. Zemlyanichkina,
M. Ziembicki,
J. Zhao,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The longitudinal polarisation transfer from muons to Λand
[`\varLambda]\bar{\varLambda}
hyperons,
DLL\varLambda([`\varLambda])D_{LL}^{\varLambda(\bar{\varLambda})}
, has been studied in deep-inelastic scattering off an unpolarised isoscalar target at the COMPASS experiment at CERN. The
spin transfers to Λand
[`\varLambda]\bar{\varLambda}
produced in the current fragmentation region exhibit different behaviours as a function of x and x
F
. The measured x and x
F
dependences of D
LL
Λ
are compatible with zero, while
DLL[`\varLambda]D_{LL}^{\bar{\varLambda}}
tends to increase with x
F
, reaching values of 0.4–0.5. The resulting average values are D
LL
Λ
= −0.012±0.047±0.024 and
DLL[`\varLambda]D_{LL}^{\bar{\varLambda}}
= 0.249±0.056±0.049. These results are discussed in the frame of recent model calculations.
European Physical Journal C 04/2012; 64(2):171-179. · 3.63 Impact Factor
-
The COMPASS Collaboration,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. Austregesilo,
B. Badełek,
F. Balestra,
J. Barth, [......],
R. Windmolders,
W. Wiślicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
J. Zhao,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: Azimuthal asymmetries in semi-inclusive production of positive (h
+) and negative hadrons (h
−) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed
in several terms according to their expected modulation in the azimuthal angle φ of the outgoing hadron. Each term receives contributions from one or several spin and transverse-momentum-dependent parton
distribution and fragmentation functions. The amplitudes of all φ-modulation terms of the hadron asymmetries integrated over the kinematic variables are found to be consistent with zero within
statistical errors, while the constant terms are nonzero and equal for h
+ and h
− within the statistical errors. The dependencies of the φ-modulated terms versus the Bjorken momentum fraction x, the hadron fractional momentum z, and the hadron transverse momentum phTp_{h}^{T} were studied. The x dependence of the constant terms for both positive and negative hadrons is in agreement with the longitudinal double-spin
hadron asymmetries, measured in semi-inclusive deep-inelastic scattering. The x dependence of the sin φ-modulation term is less pronounced than that in the corresponding HERMES data. All other dependencies of the φ-modulation amplitudes are consistent with zero within the statistical errors.
European Physical Journal C 04/2012; 70(1):39-49. · 3.63 Impact Factor
-
N. Angelov,
S. Baginyan,
F. Balestra,
Yu. Batusov,
I. Belolaptikov,
A. Bianconi,
T. Blokhintseva,
A. Bonyushkina,
V. Butenko,
M. Chiosso, [......],
B. Parsamyan,
G. Piragino,
G. Pontecorvo,
V. Pryanichnikov,
A. Rozhdestvensky,
N. Russakovich,
M. Schepkin,
I. Smirnova,
L. Venturelli,
G. F. Zosi
[show abstract]
[hide abstract]
ABSTRACT: π-4He interactions at 106MeV, with two secondary charged particles in the final state, have been studied using a self-shunted
streamer chamber in a 0.65T magnetic field and equipped with two CCD videocameras for obtaining digitized stereo-images of
nuclear events occurring within the fiducial volume of the streamer chamber. Branching ratios for the various interaction
channels are deduced. Evidence is presented for a reaction channel involving a γ produced in the final state, as well as for
the first observation of direct Δ- -resonance production. Cross-section distributions for the elastic and quasi-elastic interaction channels are also reported.
European Physical Journal A 04/2012; 34(3):255-269. · 2.19 Impact Factor
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badellek,
F. Balestra, [......],
L. Wang,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlevd,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: First measurements of azimuthal asymmetries in hadron-pair production in
deep-inelastic scattering of muons on transversely polarised ^6LiD (deuteron)
and NH_3 (proton) targets are presented. The data were taken in the years
2002-2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/c
at the CERN SPS. The asymmetries provide access to the transversity
distribution functions, without involving the Collins effect as in single
hadron production. The sizeable asymmetries measured on the NH_ target indicate
non-vanishing u-quark transversity and two-hadron interference fragmentation
functions. The small asymmetries measured on the ^6LiD target can be
interpreted as indication for a cancellation of u- and d-quark transversities.
02/2012;
-
C. Adolph,
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. A. Antonov,
A. Austregesilo,
B. Badelek,
F. Balestra, [......],
L. Wang,
R. Windmolders,
W. Wislicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: We present a determination of the gluon polarisation Delta g/g in the
nucleon, based on the longitudinal double-spin asymmetry of DIS events with a
pair of large transverse-momentum hadrons in the final state. The data were
obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon
beam scattering off a polarised ^6LiD target. The gluon polarisation is
evaluated by a Neural Network approach for three intervals of the gluon
momentum fraction x_g covering the range 0.04 < x_g < 0.27. The values obtained
at leading order in QCD do not show any significant dependence on x_g. Their
average is Delta g/g = 0.125 +/- 0.060 (stat.) +/- 0.063 (syst.) at x_g=0.09
and a scale of mu^2 = 3 (GeV/c)^2.
02/2012;
-
Collaboration,
K. Abe,
N. Abgrall,
Y. Ajima,
H. Aihara,
J. B. Albert,
C. Andreopoulos,
B. Andrieu,
M. D. Anerella,
S. Aoki, [......],
M. Yokoyama,
T. Yuan,
A. Zalewska,
J. Zalipska,
L. Zambelli,
K. Zaremba,
M. Ziembicki,
E. D. Zimmerman,
M. Zito,
J. Zmuda
[show abstract]
[hide abstract]
ABSTRACT: We report a measurement of muon-neutrino disappearance in the T2K experiment.
The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation
of the off-axis technique in a long-baseline neutrino oscillation experiment.
With data corresponding to 1.43 10**20 protons on target, we observe 31
fully-contained single muon-like ring events in Super-Kamiokande, compared with
an expectation of 104 +- 14 (syst) events without neutrino oscillations. The
best-fit point for two-flavor nu_mu -> nu_tau oscillations is sin**2(2
theta_23) = 0.98 and |\Delta m**2_32| = 2.65 10**-3 eV**2. The boundary of the
90 % confidence region includes the points (sin**2(2 theta_23),|\Delta
m**2_32|) = (1.0, 3.1 10**-3 eV**2), (0.84, 2.65 10**-3 eV**2) and (1.0, 2.2
10**-3 eV**2).
01/2012;
-
The Collaboration: N. Abgrall,
A. Aduszkiewicz,
T. Anticic,
N Antoniou,
J. Argyriades,
B Baatar,
A Blondel,
J. Blumer,
M. Bogusz,
L. Boldizsar, [......],
D. Veberic,
V. V. Vechernin,
G Vesztergombi,
A. Wilczek,
Z. Wlodarczyk,
A. Wojtaszek-Szwarc,
J. -G. Yi,
I. K. Yoo,
L. Zambelli,
W. Zipper
[show abstract]
[hide abstract]
ABSTRACT: Spectra of positively charged kaons in p+C interactions at 31 GeV/c were
measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is
based on the full set of data collected in 2007 with a graphite target with a
thickness of 4% of a nuclear interaction length. Interaction cross sections and
charged pion spectra were already measured using the same set of data. These
new measurements in combination with the published ones are required to improve
predictions of the neutrino flux for the T2K long baseline neutrino oscillation
experiment in Japan. In particular, the knowledge of kaon production is crucial
for precisely predicting the intrinsic electron neutrino component and the high
energy tail of the T2K beam. The results are presented as a function of
laboratory momentum in 2 intervals of the laboratory polar angle covering the
range from 20 up to 240 mrad. The kaon spectra are compared with predictions of
several hadron production models. Using the published pion results and the new
kaon data, the K+/\pi+ ratios are computed.
12/2011;
-
P Abreu,
M Aglietta,
E. J. Ahn,
I. F. M. Albuquerque,
D. Allard,
I. Allekotte,
J Allen,
P. Allison,
J. Alvarez Castillo,
J. Alvarez-Muñiz, [......],
G. Yuan,
A. Yushkov,
B. Zamorano,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
I Zaw,
A. Zepeda,
M. Zimbres-Silva,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: We present a comprehensive study of the influence of the geomagnetic field on
the energy estimation of extensive air showers with a zenith angle smaller than
$60^\circ$, detected at the Pierre Auger Observatory. The geomagnetic field
induces an azimuthal modulation of the estimated energy of cosmic rays up to
the ~2% level at large zenith angles. We present a method to account for this
modulation of the reconstructed energy. We analyse the effect of the modulation
on large scale anisotropy searches in the arrival direction distributions of
cosmic rays. At a given energy, the geomagnetic effect is shown to induce a
pseudo-dipolar pattern at the percent level in the declination distribution
that needs to be accounted for.
11/2011;
-
J. Abraham,
P Abreu,
M Aglietta,
C Aguirre,
E. J. Ahn,
D. Allard,
I. Allekotte,
J Allen,
J. Alvarez-Muñiz,
M. Ambrosio, [......],
T Yamamoto,
P. Younk,
G. Yuan,
A. Yushkov,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
I Zaw,
A. Zepeda,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: The surface detector array of the Pierre Auger Observatory consists of 1600
water-Cherenkov detectors, for the study of extensive air showers (EAS)
generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy,
from the identification of candidate showers at the level of a single detector,
amongst a large background (mainly random single cosmic ray muons), up to the
selection of real events and the rejection of random coincidences. Such trigger
makes the surface detector array fully efficient for the detection of EAS with
energy above $3\times 10^{18}$ eV, for all zenith angles between 0$^\circ$ and
60$^\circ$, independently of the position of the impact point and of the mass
of the primary particle. In these range of energies and angles, the exposure of
the surface array can be determined purely on the basis of the geometrical
acceptance.
11/2011;
-
The Pierre Auger Collaboration,
P Abreu,
M Aglietta,
E. J. Ahn,
I. F. M. Albuquerque,
D. Allard,
I. Allekotte,
J Allen,
P. Allison,
J. Alvarez Castillo, [......],
G. Yuan,
A. Yushkov,
B. Zamorano,
E. Zas,
D Zavrtanik,
M. Zavrtanik,
I Zaw,
A. Zepeda,
M. Zimbres-Silva,
M Ziolkowski
[show abstract]
[hide abstract]
ABSTRACT: In this paper we introduce the concept of Lateral Trigger Probability (LTP)
function, i.e., the probability for an extensive air shower (EAS) to trigger an
individual detector of a ground based array as a function of distance to the
shower axis, taking into account energy, mass and direction of the primary
cosmic ray. We apply this concept to the surface array of the Pierre Auger
Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov
stations. Using Monte Carlo simulations of ultra-high energy showers the LTP
functions are derived for energies in the range between 10^{17} and 10^{19} eV
and zenith angles up to 65 degs. A parametrization combining a step function
with an exponential is found to reproduce them very well in the considered
range of energies and zenith angles. The LTP functions can also be obtained
from data using events simultaneously observed by the fluorescence and the
surface detector of the Pierre Auger Observatory (hybrid events). We validate
the Monte-Carlo results showing how LTP functions from data are in good
agreement with simulations.
11/2011;
-
M. G. Alekseev,
V. Yu. Alexakhin,
Yu. Alexandrov,
G. D. Alexeev,
A. Amoroso,
A. Austregesilo,
B. Badelek,
F. Balestra,
J. Barth,
G. Baum, [......],
N. V. Vlassov,
R. Windmolders,
W. Wiślicki,
H. Wollny,
K. Zaremba,
M. Zavertyaev,
E. Zemlyanichkina,
M. Ziembicki,
N. Zhuravlev,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The COMPASS collaboration at CERN has investigated the \pi^- \gamma -> \pi^-
\pi^- \pi^+ reaction at center-of-momentum energy below five pion masses,
sqrt(s) < 5 m(\pi), embedded in the Primakoff reaction of 190 GeV pions
impinging on a lead target. Exchange of quasi-real photons is selected by
isolating the sharp Coulomb peak observed at smallest momentum transfers, t' <
0.001 (GeV/c)^2. Using partial-wave analysis techniques, the scattering
intensity of Coulomb production described in terms of chiral dynamics and its
dependence on the 3\pi-invariant mass m(3\pi) = sqrt(s) were extracted. The
absolute cross section was determined in seven bins of $\sqrt{s}$ with an
overall precision of 20%. At leading order, the result is found to be in good
agreement with the prediction of chiral perturbation theory over the whole
energy range investigated.
11/2011;
-
K Abe,
N. Abgrall,
Y. Ajima,
H. Aihara,
J. B. Albert,
C. Andreopoulos,
B Andrieu,
M. D. Anerella,
S Aoki,
O. Araoka, [......],
M Yokoyama,
T Yuan,
A Zalewska,
J. Zalipska,
L. Zambelli,
K Zaremba,
M Ziembicki,
E. D. Zimmerman,
M Zito,
J. Zmuda
[show abstract]
[hide abstract]
ABSTRACT: Precise measurement of neutrino beam direction and intensity was achieved
based on a new concept with modularized neutrino detectors. INGRID (Interactive
Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino
oscillation experiment. INGRID consists of 16 identical modules arranged in
horizontal and vertical arrays around the beam center. The module has a
sandwich structure of iron target plates and scintillator trackers. INGRID
directly monitors the muon neutrino beam profile center and intensity using the
number of observed neutrino events in each module. The neutrino beam direction
is measured with accuracy better than 0.4 mrad from the measured profile
center. The normalized event rate is measured with 4% precision.
11/2011;
