0 /

-/+

0

0

p/p

0, 0 Polarization at 800 GeV/c

Theo AlexopoulosNational Technical University of Athens

Outline

KTeV Experiment

Description of Polarization

Method of Measurement

KTeV Polarization Results

Summary

KTeV Experiment

’/to 10-4

E832 E799IIRare decays to 10-11

KL 0

HyperonsKS

Rare decays

Rare decays

Ran for a year in 97

KTeV99 ran in 99-00

K-P

hysics E

xp.

50m decay volume under vacuum

Highlights of the KTeV Detector

Position resolution < 1mmEnergy resolution < 1.0%

E/E

P

Pure CsI EM Calorimeter Drift Chambers Position resolution ~ 100m

Photon Veto system -system

e- from Ke3

E/P

EEE %2

%6.0

P x %00822.0%189.0 PP

What Do We Know about Hyperon Polarization(1)?

Polarization depends on Pp, production angle/targeting angle, and material of the target.Polarization reverses sign with production angle/targeting angle, and is zero at production angle =0.

Polarization is expressed as a function of transverse momentum pt =psin& momentum fraction of produced , xF=p/800

mrad

p

pp

pt

targ

et

What Do We Know about Hyperon Polarization(2)?

QCD/PQCD can’t predict anything at small pt .

Only prediction: P=0 for pt>4GeV/c

Anti-Hyperons have not been observed to be produced polarized, except for + and - in E756, E761, both with incident protons at 800 GeV/c. Anti-Hyperons were produced with the same sign and magnitude as their hyperon counterparts.

0, 0 Reconstruction

A) ppr>120GeV/cB) zppi-zlampi0>1mC) 95m<zlampi0<150mD) d>25cmE) pt2<0.001(GeV/c)2

F) (M(ppi)-1.116)<0.010GeV/c2

G) Fiducial cuts; zlampi0 in the beam holesH) proton to be confined in the beam holeI) E/P (for pion) <0.8

Analysis cuts zppi

zlam

pi00 /

-/+

00

p/p

Ξο Λ πο

Mass peaks

before cuts

after cuts

0

0

x

y

z

)cosP1)((cosdcos

dNf kkk

k

A

polarizationz

x

y

kk-

cosP21f

f

0.022-0.411 asymmetry decay

Method I:

zy,x,k , cosPff

ffkk

-

-

Method II:

Analysis Method

Hyperon production at KTeV

zy

800GeV/c protons

p

n

|p̂p̂|

p̂p̂n̂

beam

beam

pbeam

x

Bdl(18.30) Bdlhc

2

Where in nuclear magnetons, for is -1.250 and for -0.613

BNM2S1NM2S2NM2S3

P

targ

et

P

BNM2SR

P

BN

M3S

zx

yMagnet B(T) B*L(T*m) I(Amps)

rot(deg)

NM2S1 0.41 1.583 536.649 36.221NM2S2 2.17 11.905 1500 272.407NM2S3 1.06 6.18 317 141.399total 450.027NM2SR 1.304 4 2652.52 91.523NM3S 1.45 2.624 2000 No precess

Polarization Precession from sweeper Magnets

-k k k

-

f f(cos ) P cos , k x,y,z

f fR

Asymmetry measurement

Ξο Λ πο Ξο Λ πο

Polarization Results

Conclusions

0 polarization at KTeV:

002.0007.0097.0P (sys)(stat)y Average Polarization:

0 polarization at KTeV:

013.0000.0P (stat)y Average Polarization:

This result is valid for:

Ft

beamFt

xp

ppxpp

84.3

/ ,