-
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski,
H. P. Blok, [......],
C. Vogel,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
W. Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Multiplicities in semi-inclusive deep-inelastic scattering are presented for
each charge state of \pi^\pm and K^\pm mesons. The data were collected by the
HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron
beams incident on a hydrogen or deuterium gas target. The results are presented
as a function of the kinematic quantities x_B, Q^2, z, and P_h\perp. They
represent a unique data set for identified hadrons that will significantly
enhance our understanding of the fragmentation of quarks into final-state
hadrons in deep-inelastic scattering.
Physical Review D 04/2013; 87(7):14. · 4.56 Impact Factor
-
A. Airapetian,
N. Akopov,
Z. Akopov,
E.C. Aschenauer, W. Augustyniak,
A. Avetissian,
E. Avetisyan,
B. Ball,
N. Bianchi,
H.P. Blok, [......],
C. Vogel,
S. Wang,
S. Yaschenko,
H. Ye,
Z. Ye,
S. Yen,
W. Yu,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The exclusive electroproduction of rho-0 mesons was studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen target. Spin density matrix elements for this process were determined from the measured production- and decay-angle distributions of the produced rho-0 mesons. These matrix elements embody information on helicity transfer and the validity of s-channel helicity conservation in the case of a transversely polarized target. From the spin density matrix elements, the leading-twist term in the single-spin asymmetry was calculated separately for longitudinally and transversely polarized rho-0 mesons. Neglecting s-channel helicity changing matrix elements, results for the former can be compared to calculations based on generalized parton distributions, which are sensitive to the contribution of the total angular momentum of the quarks to the proton spin.
Physics Letters B 02/2013; 679:100-105. · 3.95 Impact Factor
-
A. Airapetian,
N. Akopov,
Z. Akopov,
M Amarian,
V.V. Ammosov,
A Andrus,
E.C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian, [......],
J Volmer,
C. Weiskopf,
J Wendland,
J. Wilbert,
G. Smit,
Y Ye,
Z Ye,
S. Yen,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Hard exclusive electroproduction of pi(+) pi(-) pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY Legendre moments (P-1) and (P-3) of the angular distributions of pi(+) mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the pi(+) pi(-) invariant mass can be understood as being due to the interference between relative P-wave (isovector) and S-, D-wave (isoscalar) states of the two pions. The increase in magnitude of (P-1) as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq exchange for larger values of x, which leads to a sizable admixture of isoscalar and isovector pion pairs. In addition, the interference between P-wave and D-wave states separately for transverse and longitudinal pion pairs has been studied. The data indicate that in the f(2)(1270) region at [Q(2)] = 3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component.
Phys.Lett.B599:212-222,2004. 02/2013;
-
P. Adlarson, W. Augustyniak,
W. Bardan,
M. Bashkanov,
T. Bednarski,
F. S. Bergmann,
M. Berlowski,
H. Bhatt,
M. Buescher,
H. Calen, [......],
A. Yamamoto,
X. Yuan,
L. Yurev,
J. Zabierowski,
C. Zheng,
M. J. Zielinski,
W. Zipper,
J. Zlomanczuk,
P. Zupranski,
M. Zurek
[show abstract]
[hide abstract]
ABSTRACT: An exclusive measurement of the excitation function for the dd->3Heppi-
reaction was performed at the Cooler Synchrotron COSY-Juelich with the
WASA-at-COSY detection system. The data were taken during a slow acceleration
of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold
for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The
corresponding excess energy with respect to the 4He-eta system varied from
-51.4MeV to 22MeV. The integrated luminosity in the experiment was determined
using the dd->3Hen reaction. The shape of the excitation function for the
dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An
upper limit for the cross-section for the bound state formation and decay in
the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence
level and it varies from 20nb to 27nb for the bound state width ranging from
5MeV to 35MeV, respectively.
01/2013;
-
HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski, [......],
C. Vogel,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
W. Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Multiplicities in semi-inclusive deep-inelastic scattering are presented for
each charge state of \pi^\pm and K^\pm mesons. The data were collected by the
HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron
beams incident on a hydrogen or deuterium gas target. The results are presented
as a function of the kinematic quantities x_B, Q^2, z, and P_h\perp. They
represent a unique data set for identified hadrons that will significantly
enhance our understanding of the fragmentation of quarks into final-state
hadrons in deep-inelastic scattering.
12/2012;
-
P. Adlarson, W. Augustyniak,
W. Bardan,
M. Bashkanov,
T. Bednarski,
F. S. Bergmann,
M. Berlowski,
H. Bhatt,
M. Büscher,
H. Calen, [......],
A. Yamamoto,
X. Yuan,
L. Yurev,
J. Zabierowski,
C. Zheng,
M. J. Zielinski,
W. Zipper,
J. Zlomanczuk,
P. Zupranski,
M. Zurek
[show abstract]
[hide abstract]
ABSTRACT: Exclusive and kinematically complete high-statistics measurements of the
basic double pionic fusion reactions pn -> dpi0pi0, pn -> d pi+pi- and pp ->
dpi+pi0 have been carried out simultaneously over the energy region of the ABC
effect using the WASA detector setup at COSY. Whereas the isoscalar reaction
part given by the dpi0pi0 channel exhibits the ABC effect, i.e. a low-mass
enhancement in the pipi-invariant mass distribution, as well as the associated
resonance structure in the total cross section, the isovector part given by the
dpi+pi0 channel shows a smooth behavior consistent with the conventional
t-channel Delta Delta process. The dpi+pi- data are very well reproduced by
combining the data for isovector and isoscalar contributions, if the
kinematical consequences of the isospin violation due to different masses for
charged and neutral pions are taken into account.
12/2012;
-
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
H. P. Blok,
A. Borissov, [......],
I. Vilardi,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
W. Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Beam-helicity and beam-charge asymmetries in the hard exclusive
leptoproduction of real photons from an unpolarised hydrogen target by a 27.6
GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a
missing-mass event selection technique. The asymmetry amplitudes extracted from
this data set are more precise than those extracted from the earlier data set
of 1996-2005 previously analysed in the same manner by HERMES. The results from
the two data sets are compatible with each other. Results from these combined
data sets are extracted and constitute the most precise asymmetry amplitude
measurements made in the HERMES kinematic region using a missing-mass event
selection technique.
Journal of High Energy Physics 07/2012; 1207((2012)):032/24. · 5.83 Impact Factor
-
P. Adlarson, W. Augustyniak,
W. Bardan,
M. Bashkanov,
T. Bednarski,
F. S. Bergmann,
M. Berlowski,
H. Bhatt,
K. T. Brinkmann,
M. Buescher, [......],
P. Wurm,
A. Yamamoto,
X. Yuan,
L. Yurev,
J. Zabierowski,
C. Zheng,
M. J. Zielinski,
W. Zipper,
J. Zlomanczuk,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Exclusive and kinematically complete high-statistics measurements of the
double pionic fusion reaction $dd \to ^4$He$\pi^0\pi^0$ have been performed in
the energy range 0.8 - 1.4 GeV covering thus the region of the ABC effect,
which denotes a pronounced low-mass enhancement in the $\pi\pi$-invariant mass
spectrum. The experiments were carried out with the WASA detector setup at
COSY. Similar to the observation in the basic $pn \to d \pi^0\pi^0$ reaction,
the data reveal a correlation between the ABC effect and a resonance-like
energy dependence in the total cross section. The maximum occurs at m=2.37 GeV
+ 2$m_N$, i.e. at the same position as in the basic reaction. The observed
resonance width $\Gamma \approx$ 160 MeV can be understood from broadening due
to Fermi motion of the nucleons in initial and final nuclei together with
collision damping. Differential cross sections are described equally well by
the hypothesis of a $pn$ resonance formation during the reaction process.
06/2012;
-
The HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski, [......],
V. Vikhrov,
I. Vilardi,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The beam-helicity asymmetry in exclusive electroproduction of real photons by
the longitudinally polarized HERA positron beam scattering off an unpolarized
hydrogen target is measured at HERMES. The asymmetry arises from deeply virtual
Compton scattering and its interference with the Bethe--Heitler process.
Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data
sample consisting of $ep\rightarrow ep\gamma$ events with detection of all
particles in the final state including the recoiling proton. The installation
of a recoil detector, while reducing the acceptance of the experiment, allows
the elimination of background from $ep\rightarrow eN\pi\gamma$ events, which
was estimated to contribute an average of about 12% to the signal in previous
HERMES publications. The removal of this background from the present data
sample is shown to increase the magnitude of the leading asymmetry amplitude by
0.054 +/- 0.016 to -0.328 +/- 0.027 (stat.) +/- 0.045 (syst.).
Journal of High Energy Physics 06/2012; 2012(10). · 5.83 Impact Factor
-
The Hermes collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski, [......],
I. Vilardi,
C. Vogel,
S. Wang,
S. Yaschenko,
H. Ye,
Z. Ye,
W. Yu,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Longitudinal double-spin asymmetries of charged hadrons with high transverse momentum p
T
have been measured in electroproduction using the Hermes detector at Hera. Processes involving gluons in the nucleon have been enhanced relative to others by selecting hadrons with p
T
typically above 1 GeV. In this kinematic domain the gluon polarization has been extracted in leading order making use of
the model embedded in the Monte Carlo Generator Pythia 6.2. The gluon polarization obtained from single inclusive hadrons in the p
T
range 1 GeV < p
T
< 2.5 GeV using a deuterium target is
\fracDgg(
x
,
m2
) = 0.049±0.034( stat )±0.010( sys\text-exp ) - 0.099 + 0.126( sys\text-models ) \frac{{\Delta g}}{g}\left( {\left\langle x \right\rangle, \left\langle {{\mu^2}} \right\rangle } \right) = 0.049\pm 0.034\left( {stat} \right)\pm 0.010\left( {sys\text{-}exp} \right)_{ - 0.099}^{ + 0.126}\left( {sys\text{-}models} \right) at a scale
m2
= 1.35\textGe\textV2 \left\langle {{\mu^2}} \right\rangle = 1.35\;{\text{Ge}}{{\text{V}}^2} and
x
= 0.22 \left\langle x \right\rangle = 0.22 . For different final states and kinematic domains, consistent values of
\fracDgg \frac{{\Delta g}}{g} have been found within statistical uncertainties using hydrogen and deuterium targets.
KeywordsLepton-Nucleon Scattering
Journal of High Energy Physics 04/2012; 2010(8):1-47. · 5.83 Impact Factor
-
HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski, [......],
I. Vilardi,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
W. Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: The azimuthal cos{\phi} and cos2{\phi} modulations of the distribution of
hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of
electrons and positrons off hydrogen and deuterium targets have been measured
in the HERMES experiment. For the first time these modulations were determined
in a four-dimensional kinematic space for positively and negatively charged
pions and kaons separately, as well as for unidentified hadrons. These
azimuthal dependences are sensitive to the transverse motion and polarization
of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins
effects.
04/2012;
-
The HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
A. Andrus,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetissian, [......],
S. Wang,
S. Yaschenko,
H. Ye,
Y. Ye,
Z. Ye,
S. Yen,
W. Yu,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Spin Density Matrix Elements (SDMEs) describing the angular distribution of exclusive ρ
0 electroproduction and decay are determined in the HERMES experiment with 27.6 GeV beam energy and unpolarized hydrogen and
deuterium targets. Eight (fifteen) SDMEs that are related (unrelated) to the longitudinal polarization of the beam are extracted
in the kinematic region 1<Q
2<7GeV2, 3.0<W<6.3GeV, and −t<0.4 GeV2. Within the given experimental uncertainties, a hierarchy of relative sizes of helicity amplitudes is observed. Kinematic
dependences of all SDMEs on Q
2 and t are presented, as well as the longitudinal-to-transverse ρ
0 electroproduction cross-section ratio as a function ofQ
2. A small but statistically significant deviation from the hypothesis of s-channel helicity conservation is observed. An indication is seen of a contribution of unnatural-parity-exchange amplitudes;
these amplitudes are naturally generated with a quark-exchange mechanism.
European Physical Journal C 04/2012; 62(4):659-695. · 3.63 Impact Factor
-
The HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
H. P. Blok, [......],
I. Vilardi,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
W. Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Beam-helicity and beam-charge asymmetries in the hard exclusive
leptoproduction of real photons from an unpolarised hydrogen target by a 27.6
GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a
missing-mass event selection technique. The asymmetry amplitudes extracted from
this data set are more precise than those extracted from the earlier data set
of 1996-2005 previously analysed in the same manner by HERMES. The results from
the two data sets are compatible with each other. Results from these combined
data sets are extracted and constitute the most precise asymmetry amplitude
measurements made in the HERMES kinematic region using a missing-mass event
selection technique.
03/2012;
-
A Airapetian,
N Akopov,
Z Akopov,
EC Aschenauer, W Augustyniak,
R Avakian,
A Avetissian,
E Avetisyan,
S Belostotski,
N Bianchi, [......],
V Vikhrov,
I Vilardi,
S Wang,
S Yaschenko,
Z Ye,
S Yen,
V Zagrebelnyy,
D Zeiler,
B Zihlmann,
P Zupranski
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the virtual-photon asymmetry A(2)(x, Q(2)) and of the spin-structure function g(2)(x, Q(2)) of the proton are presented for the kinematic range 0.004 < x < 0.9 and 0.18 GeV2 < Q(2) < 20 GeV2. The data were collected by the HERMES experiment at the HERA storage ring at DESY while studying inclusive deep-inelastic scattering of 27.6 GeV longitudinally polarized leptons off a transversely polarized hydrogen gas target. The results are consistent with previous experimental data from CERN and SLAC. For the x-range covered, the measured integral of g(2)(x) converges to the null result of the Burkhardt-Cottingham sum rule. The x(2) moment of the twist-3 contribution to g(2)(x) is found to be compatible with zero.
European Physical Journal C 01/2012; 72(3):7. · 3.63 Impact Factor
-
A. Airapetian,
N. Akopov,
Z. Akopov,
E. C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski,
N. Bianchi, [......],
V. Vikhrov,
I. Vilardi,
S. Wang,
S. Yaschenko,
Z. Ye,
S. Yen,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: A measurement of the virtual-photon asymmetry A_2(x,Q^2) and of the
spin-structure function g_2(x,Q^2) of the proton are presented for the
kinematic range 0.004 < x < 0.9 and 0.18 GeV^2 < Q^2 < 20 GeV^2. The data were
collected by the HERMES experiment at the HERA storage ring at DESY while
studying inclusive deep-inelastic scattering of 27.6 GeV longitudinally
polarized leptons off a transversely polarized hydrogen gas target. The results
are consistent with previous experimental data from CERN and SLAC. For the
x-range covered, the measured integral of g_2(x) converges to the null result
of the Burkhardt-Cottingham sum rule. The x^2 moment of the twist-3
contribution to g_2(x) is found to be compatible with zero.
12/2011;
-
A. Airapetian,
N. Akopov,
Z. Akopov,
E.C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski,
N. Bianchi, [......],
V. Vikhrov,
I. Vilardi,
S Wang,
S. Yaschenko,
Z Ye,
S. Yen,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Double-spin asymmetries in exclusive electroproduction of real photons from a transversely polarized hydrogen target are measured with respect to the product of target polarization with beam helicity and beam charge, and with respect to the product of target polarization with beam helicity alone. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe--Heitler process. They are related to the real part of the same combination of Compton form factors as that determining the previously published transverse target single-spin asymmetries through the imaginary part. The results for the double-spin asymmetries are found to be compatible with zero within the uncertainties of the measurement, and are not incompatible with the predictions of the only available GPD-based calculation.
Physics Letters B 10/2011; 704(1-2):15-23. · 3.95 Impact Factor
-
A. Airapetian,
N. Akopov,
Z. Akopov,
E.C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski,
N. Bianchi, [......],
C Vogel,
S Wang,
S. Yaschenko,
Z Ye,
S. Yen,
W Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Hadron multiplicities in semi-inclusive deep-inelastic scattering were measured on neon, krypton, and xenon targets relative to deuterium at an electron(positron)-beam energy of 27.6GeV at HERMES. These ratios were determined as a function of the virtual-photon energy ν , its virtuality Q2, the fractional hadron energy z and the transverse hadron momentum with respect to the virtual-photon direction pt. Dependences were analysed separately for positively and negatively charged pions and kaons as well as protons and antiprotons in a two-dimensional representation. Compared to the one-dimensional dependences, some new features were observed. In particular, when z > 0.4 positive kaons do not show the strong monotonic rise of the multiplicity ratio with ν as exhibited by pions and negative kaons. Protons were found to behave very differently from the other hadrons.
European Physical Journal A 09/2011; 47(113). · 2.19 Impact Factor
-
P. Adlarson,
C. Adolph, W. Augustyniak,
W. Bardan,
M. Bashkanov,
T. Bednarski,
F. S. Bergmann,
M. Berłowski,
H. Bhatt,
K. -T. Brinkmann, [......],
P. Wüstner,
P. Wurm,
X. Yuan,
L. Yurev,
J. Zabierowski,
C. Zheng,
M. J. Zieliński,
W. Zipper,
J. Złomańczuk,
P. Żuprański
[show abstract]
[hide abstract]
ABSTRACT: An exclusive measurement of the decay eta --> pi+ pi- gamma has been
performed at the WASA facility at COSY. The eta mesons were produced in the
fusion reaction pd --> 3He X at a proton beam momentum of 1.7 GeV/c. Efficiency
corrected differential distributions have been extracted based on 13340\pm140
events after background subtraction. The measured pion angular distribution is
consistent with a relative p-wave of the two-pion system, whereas the measured
photon energy spectrum was found at variance with the simplest gauge invariant
matrix element of eta --> pi+ pi- gamma. A parameterization of the data can be
achieved by the additional inclusion of the empirical pion vector form factor
multiplied by a first-order polynomial in the squared invariant mass of the pi+
pi- system.
07/2011;
-
HERMES Collaboration,
A. Airapetian,
N. Akopov,
Z. Akopov,
E.C. Aschenauer, W. Augustyniak,
R. Avakian,
A. Avetissian,
E. Avetisyan,
S. Belostotski, [......],
C Vogel,
S Wang,
S. Yaschenko,
Z Ye,
S. Yen,
W Yu,
V. Zagrebelnyy,
D. Zeiler,
B. Zihlmann,
P. Zupranski
[show abstract]
[hide abstract]
ABSTRACT: Hadron multiplicities in semi-inclusive deep-inelastic scattering were
measured on neon, krypton and xenon targets relative to deuterium at an
electron(positron)-beam energy of 27.6 GeV at HERMES. These ratios were
determined as a function of the virtual-photon energy nu, its virtuality Q2,
the fractional hadron energy z and the transverse hadron momentum with respect
to the virtual-photon direction pt . Dependences were analysed separately for
positively and negatively charged pions and kaons as well as protons and
antiprotons in a two-dimensional representation. Compared to the
one-dimensional dependences, some new features were observed. In particular,
when z > 0.4 positive kaons do not show the strong monotonic rise of the
multiplicity ratio with nu as exhibited by pions and negative kaons. Protons
were found to behave very differently from the other hadrons.
07/2011;
-
P. Adlarson,
C. Adolph, W. Augustyniak,
M. Bashkanov,
T. Bednarski,
F. S. Bergmann,
M. Berłowski,
H. Bhatt,
K. -T. Brinkmann,
M. Büscher, [......],
P. Wüstner,
P. Wurm,
X Yuan,
L. Yurev,
J. Zabierowski,
C Zheng,
M. J. Zieliński,
W. Zipper,
J. Złomańczuk,
P. Zuprański
[show abstract]
[hide abstract]
ABSTRACT: The reaction pp->pppi0pi0 has been investigated at a beam energy of 1.4 GeV
using the WASA-at-COSY facility. The total cross section is found to be (324 +-
21_systematic +- 58_normalization) mub. In order to to study the production
mechanism, differential kinematical distributions have been evaluated. The
differential distributions indicate that both initial state protons are excited
into intermediate Delta(1232) resonances, each decaying into a proton and a
single pion, thereby producing the pion pair in the final state. No significant
contribution of the Roper resonance N*(1440) via its decay into a proton and
two pions is found
07/2011;
