DIRECT RECONSTRUCTION OF THE AMPLITUDES OF THE pp→dπ+ REACTION AT 447, 515 AND 580 MeV

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DIRECT RECONSTRUCTION OF THE

AMPLITUDES OF THE pp → dπ+ REACTION AT 447, 515 AND 580 MeV

G. Gaillard, G. Cantale, E. Heer, R. Hess, C. Lechanoine-Leluc, D. Rapin

To cite this version:

G. Gaillard, G. Cantale, E. Heer, R. Hess, C. Lechanoine-Leluc, et al.. DIRECT RECONSTRUCTION

OF THE AMPLITUDES OF THE pp → dπ+ REACTION AT 447, 515 AND 580 MeV. Journal de

Physique Colloques, 1990, 51 (C6), pp.C1-387-C1-390. �10.1051/jphyscol:1990635�. �jpa-00230902�

COLLOQUE DE PHYSIQUE

C o l l o q u e C 6 , s u p p l 6 m e n t au n 0 2 2 , T o m e 5 1 , 1 5 n o v e m b r e 1 9 9 0

DIRECT RECONSTRUCTION OF THE AMPLITUDES OF THE pp-+dnf REACTION AT 447, 515 AND 580 MeV

G . GAILLARD, G . CANTALE, E . HEER, R . HESS, C . LE'CHANOINE-LELuC and D . RAPIN

DPNC Universite de Geneve, 24 Quai Ansermet, CH-1211 Geneve 4 , Switzerland

Rksumk : La reconstruction directe des amplitudes de diffusion de la reaction pp -+ dn+ a dtk rbalisk par le groupe de GenBve & 447, 515 et 580 MeV & 8 angles centre-de-masse du deuton, compris entre 52.5' et 87.5'. Les rbsultats dbfinitifs & 580 MeV sont prbentbs.

Abstract : The Geneva group has performed a direct, model independent, reconstruction of the scattering amplitudes of the pp -+ dn+ reaction at 447, 515 and 580 MeV at 8 deuteron center-of-mass angles between 52.5' and 87.5O. FinaI results a t 580 MeV are presented.

1 Introduction

The first amplitude reconstruction published by the Geneva group [I] was challenged by the result of the measurement of the spin transfer coefficient Kss performed at TRIUhlF[2]. This forced us to check the analysis and allowed us to uncover that an error in the sign of the longitudinal and sideway polarizations of the primary proton beam had occured during the analysis of the spin transfer coefficients. This error lead to a sign inversion in the asymmetries e,(X), E ~ , ( X ) , e,(Z) and E ~ , ( Z ) (see [I] for a complete description of the formalism used here). The amplitude analysis has now been redone with the correct signs for the four above asymmetries.

2 The Amplitude Analysis

Six complex amplitudes are necessary to fully describe the scattering matrix of the pp -+ d ~ + reaction.

One overall phase beeing experimentally unreachable, one has to determine 11 real quantities : 6 modules and 5 phases. In our case, the analysing powers of the Carbon polarimeter which analysed the deuteron polarisation were unknown (except for

Tm

which we took equal to 0 [3j) and had to be treated as free parameters in the analysis, raising the number of unknowns to 14.

Over the years, the Geneva group had measured many observables for the pp + daf reaction, starting with differential cross section[4] continuing with analysing powers A,, and A,, and spin correlation coef- ficients A,,, A,,, Akk and A,k[5][6] and finally ending with spin transfer coefficients eC(O), ezc(0), e C ( f y), c z c ( f y), cs(X), E,(Z), e2,(X) and eZs(Z)[l]. A total of 17 observables was then measured at each energy and angle. In additicn, the Pauli principle allow us to express the above E'S measured at an angle n - 0 by means of the amplitudes a t angle 0. One could then add 10 new observables E(T

-

0) by introducing only 3 new parameters, the 3 polarimeter analysing powers at n

-

0. The amplitude analysis consisted finally in fitting 27 measured observables by means of 17 free parameters.

3 Results and Discussion

Figure 1 shows the polarimeter effective analysing powers obtained from the analysis compared with two measurements carried out at Saclay with experimental set-up similar to the Geneva polarimeter[3] [7].

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990635

C6-388 COLLOQUE DE PHYSIQUE

Figure 1 : Effective d-C analysing powers of the po- larimeter. The Madison convention's definitions are used here.

Figures 2 and 3 show the reconstructed amplitudes compared with theoretical calculations due to Locher[S]

[9], the Lyon group[lO], Blankleiderjll], Niskanenfl21 and Rinat[l3] and with two partial waves analyses due to Bugg[l4] and Watari[l5]. It is visible that the theoretical calculations have problems reproducing the data : the difference between the modules of amplitudes A and C is underestimated and large discrepancies exist between the different predictions for amplitudes D, E and F. Moreover, most theoretical calculations tend to minimize the modules of these amplitudes. All these feature confirm the tendency already pointed out [I] [9], that the proton-proton spin triplet strength is underestimated by the theoretical models.

References

[I] G. Cantale et al. Helv. Phys. Acta, 66(1987)398.

[2] D. A. Hutcheon et al. Nucl. Phys., A503(1989)649.

[3]

M.

G a r p n et al. Nucl. Phys., A458(1986)287.

[4] D. Aebischer et al. Nucl. Phys., B106(1976)214.

[5] E. Aprile et al. hTuc1. Phys., A379(1982)369.

[6] E. Aprile et al. Nucl. Phys., A415(1984)365.

[7] B. Bonin et al. POMME, a medium energy deuteron polarimeter based on semi-inclusive d-Carbon scattering. Submitted to N.I.hf.

[8] M. P. Locher and A. Svarc. J. Phys. G, 11(1985)183.

[9] M. P. Locher and A. Svarc. Few Body Sys., 5(1988)59.

[I01

C.

Fayard et al. Few Body XI1 Vancouver 1989, G. H. Lamot private communication.

[ l l ] B. Blankleider and I. R. Afnan. Phys. Rev. C, 31(1985)1380.

[12] J. A. Niskanen. Phys. Lett., 141B(1984)301.

[13] A. S. Rinat and Y. Starkand. ^n'ucl. Phys., A397(1983)381.

[14] D. V. Bugg, A. Hasan, and R. L. Shypit. ^ATucl. Phys., A477(1988)546.

[15] W. \Vatxi N. Hiroshige and hl. Yoneza~va. Prog. Theor. Phys., 72(1984)1146.

,,-- Locher 1

---

^Locher 2

Figure 2 : hlodules of the helicity amplitudes a t 580 RleV in

J-~

vs. O:,,,. The d a t a a t O0 and 90' are from E. Aprile-Giboni et al. iVucl. Phys. A415(1984)391.

1 .o

:

^[(mb/=fi

ICl i ^:

^[(mb/up)

0.8

.-.-.-.

Blankleider

-

^Rinat

: ...

Niskanen

: ...

^Bugg

:

Watari

ID1 i

0.6

...

0. 30 60 W 0. 30 60

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S c a t t e r i n g A m p l i t u d e s

-

.

[ d l

. - - - -

Locher 1 .

-

^Lyon

+

p p + d n 580 MeV

1 " . . . I . . 1

Blankleider

... Niskanen

Figure 3 : Phases of the helicity amplitudes at 580 MeV in radian vs. 6&.