HAL Id: jpa-00221860
https://hal.archives-ouvertes.fr/jpa-00221860
Submitted on 1 Jan 1982
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
PROGRESS REPORT ON THE HIGH RESOLUTION SPECTROMETER
L. Price
To cite this version:
L. Price. PROGRESS REPORT ON THE HIGH RESOLUTION SPECTROMETER. Journal de
Physique Colloques, 1982, 43 (C3), pp.C3-43-C3-44. �10.1051/jphyscol:1982307�. �jpa-00221860�
JOURNAL DE PHYSIQUE
CoZZoque ~ 3 , supple'ment au n o 1 2 , Tome 43, de'cembre 1982 page C3-43
PROGRESS REPORT ON T H E H I G H R E S O L U T I O N SPECTROMETER L.E. P r i c e
Argonne NationaZ Laboratory, 9700 South Cass Ave. Argonne, IZZinois 60439 U. S. A.
The High Resolution Spectrometer a t PEP i s a general purpose e'e- solenoidal detec- t o r which has been designed t o emphasize c h a r g e d - p a r t i c l e t r a c k i n q and hence momentum r e s o l u t i o n and e f f e c t i v e mass r e s o l u t i o n . The h i g h r e s o l u t i o n i s achieved by means o f a 1.6 Tesla magnetic f i e l d and t r a c k i n g t o a r a d i u s o f almost 2m. The major p r o - p e r t i e s o f t h e d e t e c t o r a r e given i n Table I. I t has been b u i l t by groups from Argonne, Indiana, Vichigan, Purdue, SLAC, and Berkeley. While t h e HRS was f i r s t exposed t o beam i n November 1982, and took a week o f data i n December, t h e major r u n was from February t o June, 1982. Production a n a l y s i s began i n Yay, 1982 w i t h 65% o f t h e data from t h e 24,000 nb-1 i n t e q r a t e d l u m i n o s i t y a l r e a d y p u t through t h e f i r s t pass ( f i l t e r i n g ) o f a n a l y s i s and ?5% r e c o n s t r u c t e d so f a r .
C l e a r l y , reconstructed events have been a v a i l a b l e f o r too s h o r t a time f o r me t o be a b l e t o q i v e d e f i n i t i v e r e s u l t s on t h e c a p a b i l i t i e s o f t h e HRS.
Vuch work has a l r e a d y been done, however, t o c a l i b r a t e and understand each of t h e d e t e c t o r components, so I w i l l summarize t h e c u r r e n t s t a t u s . I t should be kept i n mind, however, t h a t most o f these numbers are s t i l l improving r a p i d l y .
A cross-section of t h e detector, b u i l t i n s i d e t h e magnet (somewhat m o d i f i e d ) f r o m t h e Argonne 1 2 - f o o t Bubble Chamber, i s shown i n F i g u r e 1 as designed.
Summary o f HRS performance as o f J u l y , 1982 :
1. Residuals i n t h e i n n e r d r i f t chamber f o r t r a c k s f i t i n a l l d r i f t chamber l a y e r s average 170 urn, already b e t t e r than t h e desiqn o f 200 um.
2. Momentum r e s o l u t i o n f o r Bhabha s c a t t e r e d e l e c t r o n t r a c k s o f 14.5 GeV/c has qp = 0.38 5eV/c o r ap/p = 0.0018 p. tllhile t h i s i s already b e t t e r by a s i z e a b l e f a c t o r than o t h e r e+e- detectors, i t should improve by c l o s e t o a f a c t o r o f 2 when t h e alignment between i n n e r and o u t e r d r i f t chambers i s completely understood.
3. Time o f f l i g h t r e s o l u t i o n i n t h e b a r r e l c a l o r i m e t e r i s a = 165 ps f o r Bhabha e l e c t r o n s , which g i v e very l a r g e s i g n a l s , and o = 400 ps (and s t i l l q e t t i ng b e t t e r ) f o r minimum i o n i z i n q hadrons.
4. F i r s t looks a t well-known d i s t r i b u t i o n s such as charged p a r t i c l e m u l t i p l i c i - t i e s , QCD j e t parameters, and Bhabha e l e c t r o n anaular d i s t r i b u t i o n s show agreement w i t h previous r e s u l t s o r w i t h theory.
+ -
5. One e f f e c t i v e mass has been c a l c u l a t e d so f a r , t h a t o f t h e K:
+ Tn , f o r which we q e t a d i s t r i b u t i o n w i t h om.= 4 \lev. As w i t h much o f o u r a n a l y s i s a t t h i s e a r l y stage, t h e measured KO resolution was improving almost d a i l y , w h i l e a l r e a d y being t h e b e s t i n t h e f i e l d .
Ouring t h e c u r r e n t summer shut down o f PEP, two s i g n i f i c a n t a d d i t i o n s a r e being made t o t h e HQS. One i s a system o f 832 p h o t o i o n i z i n q Cerenkov counters t o do K/T sepa- r a t i o n from 1 t o 4 GeV/c. The o t h e r i s a 336 w i r e Vertex Detector w i t h a r e s o l u t i o n of 100 pm. By t h e time PEP t u r n s on i n t h e f a l l , we expect t o have t h e d e t e c t o r f u l l y c a l i b r a t e d and t o he analyzing t h e spring,1982 data, w h i l e t h e HQS, w i t h enhan- ced p a r t i c l e i d e n t i f i c a t i o n added t o t h e unique momentum r e s o l u t i o n , continues t o t a k e new data.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982307
JOURNAL DE PHYSIQUE
TABLF. I
PSOPERTIES 3F THE H I G H RESOLUTION SPECTROYETER Tracking
Yagnetic F i e l d (Superconducting blagnet) D r i f t Chambers
a ) Inner Radii
Number of 1 ayers Number of c e l l s S o l i d angle b) Outer
Radii
Number of l a y e r s Number of c e l l s S o l i d a n g l e Reconstruction p r e c i s i o n
%mentun r e s o l u t i o n (Hiqh p l i m i t ) Electromagnetic Calorimetry
Angular r e s o l u t i o n (one pwc l a y e r ) Number of modules ( P b / s c i n t i l l a t o r ) Energy r e s o l u t i o n
e/rr s e p a r a t i o n P a r t i c l e I d e n t i f i c a t i o n
a ) Time o f F l i g h t Time r e s o l u t i o n a t r - 2m
K/n s e p a r a t i o n P/K s e p a r a t i o n b) Cerenkov (adding now) Number o f c e l l s Solid angle K/n s e p a r a t i o n P/K,n s e n a r a t i o n
1.6 Tesla
F.