-
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;
-
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
-
D. Eversheim,
F. Hinterberger, R. Jahn,
D. Samuel,
J. Dietrich,
A. Lehrach,
D. Prasuhn,
R. Gebel,
O. Felden,
M. Beyer,
W. Kretschmer
[show abstract]
[hide abstract]
ABSTRACT: For the Time Reversal Invariance experiment at COSY (TRIC) that had been proposed at the Forschungszentrum Jülich a novel
technique for measuring total cross sections in internal experiments was developed and the achievable precision of this measuring
technique was tested. The experimental idea constitutes a true P-even T-odd null test of TRI. In order to compare to the theoretical
upper bound from edm measurements (Haxton and Höring, Nucl Phys A560:469, 1993), the TRI violating observable A
y,xz
in proton-deuteron forward scattering has to be measured with an accuracy of 10 − 6. An internal TRI experiment can determine the total cross section via the optical theorem by measuring the forward scattering
amplitude. In contrast to external experiments, the only calibrated device that is needed is a precise beam current transformer
(BCT). The feasibility of an internal TRI experiment was tested at COSY in a measurement of A
y,y
in p-p scattering, since these values are known. The analysis of the data showed the presence of unexpected large 1/f noise contributions, which eventually reduced the achievable accuracy by a factor 3. The origin of the 1/f noise was traced and found to be the Barkhausen noise from the ferrite-core of the BCT. A global weighted fitting technique
based on a modified Wiener-Khinchin method was applied to suppress the influence of the 1/f noise.
Hyperfine Interactions 04/2012; 193(1):335-339. · 0.21 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
-
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;
-
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;
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
P. Hawranek,
F. Hinterberger, R Jahn,
R Joosten,
K. Kilian,
Da. Kirillov,
Di. Kirillov, [......],
J. Ritman,
P. von Rossen,
J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and
\Theta = 0 deg with a high missing mass resolution in order to study the Lambda
p final state interaction. Narrow S = -1 resonances predicted by bag model
calculations are not visible in the missing mass spectrum. Small structures
observed in a previous experiment are not confirmed. Upper limits for the
production cross section of a narrow resonance are deduced for missing masses
between 2058 and 2105 MeV/c^2.
05/2011;
-
A. Budzanowski,
A. Chatterjee,
P. Hawranek, R. Jahn,
V. Jha,
K. Kilian,
S. Kliczewski,
Da. Kirillov,
Di. Kirillov,
D. Kolev, [......],
N. Piskunov,
D. Protić,
J. Ritman,
P. von Rossen,
B. J. Roy,
I. Sitnik,
R. Siudak,
R. Tsenov,
J. Urban,
G. Vankova
[show abstract]
[hide abstract]
ABSTRACT: The cross section for the reaction $p+^6\text{Li}\to\eta+^7\text{Be}$ was
measured at an excess energy of 11.28 MeV above threshold by detecting the
recoiling $^7$Be nuclei. A dedicated set of focal plane detectors was built for
the magnetic spectrograph Big Karl and was used for identification and four
momentum measurement of the $^7$Be. A differential cross section of
$\frac{d\sigma}{d\Omega}=(0.69\pm{0.20}\text{(stat.)}\pm
0.20\text{(syst.)})\text{nb/sr}$ for the ground state plus the 1/2$^-$ was
measured. The result is compared to model calculations.
10/2010;
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger, R Jahn,
R Joosten,
K. Kilian,
S. Kliczewski, [......],
D. Protic,
J. Ritman,
P. von Rossen,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: We have measured inclusive data on $K^+$-meson production in $pp$ collisions at COSY J\"ulich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $\Lambda p$, $\Sigma^0p$ and $\Sigma^+n$. The cross section for the $\Sigma^+n$ channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence. Comment: accepted by Phys. lett. B some typos corrected
07/2010;
-
M G Alekseev,
V Yu Alexakhin,
Yu Alexandrov,
G D Alexeev,
A Amoroso,
A Austregesilo,
B Badełek,
F Balestra,
J Ball,
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: The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the π- π- π+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420,000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV2/c2. The well-known resonances a1(1260), a2(1320), and π2(1670) are clearly observed. In addition, the data show a significant natural-parity exchange production of a resonance with spin-exotic quantum numbers J(PC)=1-+ at 1.66 GeV/c2 decaying to ρπ. The resonant nature of this wave is evident from the mass-dependent phase differences to the J(PC)=2-+ and 1++ waves. From a mass-dependent fit a resonance mass of (1660±10(-64)(+0)) MeV/c2 and a width of (269±21(-64)(+42)) MeV/c2 are deduced, with an intensity of (1.7±0.2)% of the total intensity.
Physical Review Letters 06/2010; 104(24):241803. · 7.37 Impact Factor
-
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger, R Jahn,
R Joosten,
K. Kilian,
S. Kliczewski, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp -> K+ + (Lambda p) was measured at Tp=1.953 GeV and Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. The large final state enhancement near the Lambda p threshold can be described using the standard Jost-function approach. The singlet and triplet scattering lengths and effective ranges are deduced by fitting simultaneously the Lambda p invariant mass spectrum and the total cross section data of the free Lambda p scattering. Comment: submitted to Physics Letters B, 10 pages, 3 figures
03/2010;
-
The HIRES Collaboration,
A. Budzanowski,
A. Chatterjee,
H. Clement,
E. Dorochkevitch,
P. Hawranek,
F. Hinterberger, R Jahn,
R Joosten,
K. Kilian, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
A. Sibirtsev,
I. Sitnik,
R. Siudak,
R. Tsenov,
K. Ulbrich,
J. Urban,
G. J. Wagner
11/2009;
-
A. Budzanowski,
A. Chatterjee,
P. Hawranek, R Jahn,
V. Jha,
K. Kilian,
Da. Kirillov,
Di. Kirillov,
S. Kliczewski,
D Kolev, [......],
J. Ritman,
P. von Rossen,
B. J. Roy,
I. Sitnik,
R. Siudak,
H. J. Stein,
R. Tsenov,
J. Urban,
G. Vankova,
C. Wilkin
[show abstract]
[hide abstract]
ABSTRACT: Inclusive measurements of pion production in proton--proton collisions in the forward direction were undertaken at 400 and 600 MeV at COSY using the Big Karl spectrograph. The high resolution in the $\pi^+$ momentum ensured that there was an unambiguous separation of the $pp\to {\pi}^+d/\pi^+pn$ channels. Using these and earlier data, the ratio of the production cross sections could be followed through the $\Delta$ region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final $pn$ system. These have been investigated in a realistic $pp\to\pi^+d/\pi^+pn$ calculation that includes $S \rightleftharpoons D$ channel coupling between the final nucleons. A semi-quantitative understanding of the observed effects is achieved. Comment: 10 pages, 3 figures
04/2009;
