Exclusive $\rho ^0$ meson photoproduction with a leading neutron at HERA

Andreev, V.; Baghdasaryan, A.; Begzsuren, K.; Belousov, A.; Bolz, A.; Boudry, V.; Brandt, G.; Brisson, V.; Britzger, D.; Buniatyan, A.

doi:10.1140/epjc/s10052-015-3863-1

Exclusive $\rho ^0$ meson photoproduction with a leading neutron at HERA

H1

Collaboration

•

V. Andreev
(
- Lebedev Inst.
)

Aug 13, 2015

39 pages

Published in:

Eur.Phys.J.C 76 (2016) 1, 41

Published: Jan 23, 2016

e-Print:

1508.03176 [hep-ex]

DOI:

10.1140/epjc/s10052-015-3863-1

Report number:

DESY-15-120

Experiments:

DESY-HERA-H1

View in:

datasets

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Abstract: (Springer)

A first measurement is presented of exclusive photoproduction of

\rho ^0

mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years 2006 and 2007 at a centre-of-mass energy of

\sqrt{s}=319

GeV and correspond to an integrated luminosity of 1.16 pb

^{-1}

. The

\rho ^0

mesons with transverse momenta

p_T<1

GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum,

x_L>0.35

, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality

Q^2 < 2

GeV

^2

, the total energy of the photon–proton system

20 < W_{\gamma p}< 100

GeV and the polar angle of the leading neutron

\theta _n < 0.75

mrad. The cross section of the reaction

\gamma p \rightarrow \rho ^0 n \pi ^+

is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a

\rho ^0

meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering,

\sigma ^\mathrm{el}(\gamma \pi ^+ \rightarrow \rho ^0\pi ^+)

, is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction

\gamma p \rightarrow \rho ^0 n \pi ^+

.

Note:

38 pages, 13 figures, 10 tables, this version accepted by EPJC

electron p: colliding beams
electron p: deep inelastic scattering
pi: exchange
rho(770)0: photoproduction
mass spectrum: (pi+ pi-)
rho(770)0: hadronic decay
p: momentum
DESY HERA Stor
transverse momentum
electron p: exclusive reaction

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