POLARIZED BEAM PROTON-ANTIPROTON COLLIDERS

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Submitted on 1 Jan 1985

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POLARIZED BEAM PROTON-ANTIPROTON COLLIDERS

D. Cline

To cite this version:

D. Cline. POLARIZED BEAM PROTON-ANTIPROTON COLLIDERS. Journal de Physique Col-

loques, 1985, 46 (C2), pp.C2-733-C2-736. �10.1051/jphyscol:1985296�. �jpa-00224615�

POLARIZED BEAM PROTON-ANTIPROTON COLLIDERS

D. C I i n e

University of Wisconsin, Madison 53706, U.S.A.

Résumé

Nous discutons les possibilités pour les collisions de protons polarisées lon- gitudinalement avec des antiprotons non-polarisês. Le but le plus important est sans doute la détection de la composante V+A des particules W-. Nous donnons une brève discussion de la possibilité de produire des antiprotons polarisés dans un anneau d'accumulation au CERN et à FNAL,

Abstract

We discuss some of the physics possibilities for collisions of longitudinally polarized protons with unpolarized antiprotons. Perhaps the most important goal is the detection of a (V+A) component of the W- particles. A brief discussion is given of the possibility of producing polarized antiprotons in the accumulator rings at CERN and FNAL.

Measurements of a^ Possible (V+A) Component of the Weak Interaction Using Polarized pp Collisions

The production of W* bosons with polarized proton or antiproton beams can provide a sensitive test of a possible V+A component to the weak force. This in turn can be interpreted as a component of the mixing between left-handed and right-handed W-. Already the UA1 experiment has set limits on such a component by studying the charged lepton angular distribution in the center of mass as shown in Fig. 1. The V+A component would appear as at cos 9 = - 1 . Future studies of W- decays should reduce this limit by about a factor of 10 and then the effect of W- production by gluonic processes. In order to go further it will be necessary to use polarized pp collisions in order to align the production qq system.

The V-A structure of the W- leads to a well known charge asymmetry of the A- that came from W-->i-+ve decay. This charge asymmetry is shown in Fig. 2a,b for the case of pp collisions at v's = 540 GeV and /§ = 2000 GeV.2 There is a component of wrong sign-wrong angle leptons coming from QCD processes. At very small angles the charge asymmetry is very pronounced because these particles largely come from the part of the W + £+ve angular range near cos 9 = ±1. A test of this angular asymmetry will be carried out using the forward muon spectrometer in the CDF detector at Fermilab being constructed by the Wisconsin group. The expected angular distribution is shown in Fig. 2c.

Possibility of Polarized p Beams in pp Collider

If polarized p sources could be used the possibility of pp collisions would be realized. Although sources of energy polarized p's have very low interesting (i.e., A+p+. .) it may be possible to polarize the p in the storage rings used to collect and store the p's. Two possibilities for this possibility have been suggested:

1. Collisions between $ and p in adjacent storage rings at a very low P^ of Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985296

JOURNAL DE PHYSIQUE

the f5p of the pp system with a possible $ to

f5

2. Differential absorption of certain spin components of the p's using

p+

Nucleus collisions with polarized targets.

The addition of polarized pp collisions can greatly enhance the V+A structure in these experiments. Detailed Monte Carlo results are needed to further determine the sensitivity to V+A currents.

The low PI region has a large component of events that come from k,e

This is also the region where new processes such as heavy leptons

and supersymmetric particles such as W, 2 give large contributions. The study of this region will polarized pp collisions may be necessary to unravel all the possible processes involved (see Fig. 2b).

Finally a test of CP invariance may be possible using polarized pi5 collisions by comparing

f i

fi

eif

At present neither of these techniques have been worked out due to the lack of information about the partial wave amplitudes of low energy

-F(g)

interactions. However with the experiments at the LEAR ring sufficient information may be available in the near future. At any rate it seems unlikely that these techniques will 1 ad to high intensity-sources and for the near future it Is most likely that

&

The amplitudes for W production and decay using polarized Fp collisions are shown in Fig. 3a and 3b for & = 540 GeV and 2000 GeV (private communication, R. Kinnunen). These calculations show the sensitivity of the W coupling.3

It is clear that polarized pp collisions will be a very important addition to collider physics.

References 1. G. Arnison, et al., Phys Lett. 103 (1983).

2. D. Cline and C. Rubbia, CERN EP/83-61 and published in Phys Lett.

3 . R. Kinnunen, private communication.

Discussion

Prof. A.D. Krisch made a point related to the question of polarized anti- protons. He recalled some suggestions made at the Vancouver Meeting on Polarized Ion Sources involving a polarized electron source such that used by SLAC-YALE.

Techniques analogous to those for polarized targets consist in putting in some magnetic fields and RF microwave towers, high frequency boosts and hyperfine transitions to transfer electron polarization to protons.

cos

Q*

F i g . 1

F i g . 2a

At

FNAL

8

-

6

-

5 -

1 0 - 1

cos 8

Fig. 2b

F i g

.

JOURNAL DE PHYSIQUE