Alignment of the ZEUS Micro- Vertex Detector Using Cosmic Tracks

Transcription

1 Alignment of the ZEUS Mico- Vetex etecto Using Cosmic acks akanoi Kohno (Univesity of Oxfod), ZEUS MV Goup Intenational Wokshop on Advanced Computing and Analysis echniques in Physics Reseach (ACA5) ESY, Zeuthen, May -7, 5 ACA5, ESY, Zeuthen 1

2 Contents HERA-II and the ZEUS detecto upgade. Alignment of the Mico-Vetex etecto (MV) Results Summay & Conclusion ACA5, ESY, Zeuthen

3 ZEUS expeiment HERA: Electon-poton collide at ESY, Hambug. E p 9 GeV E e 7.5 GeV ZEUS BMUON RMUON p ZEUS detecto: Multi-pupose paticle detecto FCAL BCALRCAL C e Y Z ACA5, ESY, Zeuthen 3

4 HERA-II and ZEUS Upgade HERA upgade Luminosity incease ( 5) Electon longitudinal polaization. C ZEUS detecto upgade Mico-Vetex etecto (MV) Polaization depended chaged cuent inteaction. Impove the efficiency of tagging cham and beauty paticles using thei lifetime infomation. ACA5, ESY, Zeuthen 4

5 ZEUS Mico-Vetex etecto (MV) Motivation of installing the MV Pecise tacking of chaged paticle nea the inteaction point. Reconstuction of seconday vetex fom longlived paticles, like c- o b-hadons. Single-sided Si stip senso with 1 µm eadout pitch (intemediate stips : µm) Pecise position measuement equied! FMV BMV ACA5, ESY, Zeuthen 5

6 Alignment of the MV Position measuement of the hit on a senso ~ µm. ack econstuction : fitting hits on vaious sensos with a helix. Necessay to know eal positions of sensos at high pecision. Fom the 3 suvey duing constuction, we know positions of sensos on each ladde wee measued to 5 µm duing constuction. Most unknown factos elative positions of laddes position of the entie MV wt. ZEUS. Knowledge of eal positions of laddes. Alignment Goal : Alignment pecision < 1 µm. ACA5, ESY, Zeuthen 6

7 Alignment method Basic stategy Use paticle tacks and minimize the esiduals between the hit and the tack. Befoe Q P χ all hits in all tacks Q : hit position P : tack intesection ( ) + Q P ' : fo afte movement Measuable Small lineaize wt. alignment paametes : v a x Afte Q P ACA5, ESY, Zeuthen 7

8 ACA5, ESY, Zeuthen 8 χ minization ( ) ( ) { } ,, 1 ) ( χ χ a v aa M v M a aa a a Alignment paametes : calculated by one 6 6 matix invesion + matix-vecto poduct

9 Alignment using cosmic tacks 3 laddes in 3 layes 3 tanslation + 3 otation degees of feedom 18 paametes Advantage acks with many MV hits. Less ambiguities in patten ecognition. isadvantage Non-unifom angula coveage. Only possible fo the bael MV. Needs a special cosmic un. ack sample (cosmic muons) : Rate ~ few Hz 1 week of dedicated cosmic uns 6k cosmic tacks fo the alignment. ACA5, ESY, Zeuthen 9

10 Alignment pocedue Global alignment (x 1) ZEUS fame MV fame ladde fame ladde fame Intenal alignment (x 5) ladde fame ladde fame Global alignment (x 1) Iteation is needed in each step due to, 1. the linea appoximation used in the fomula and. fo the intenal alignment, alignment of one ladde depends on the geomety of othe laddes. ACA5, ESY, Zeuthen 1

11 ACA5, ESY, Zeuthen 11 Global alignment ( ) 3 1 v v R R R a Y Z Y Z Z Y Z Y i i φ hit -z hit Extapolate the C tack into the MV. esidual infomation 3 position of the hit. 1,, a v aa M v M

12 Effect on esidual distibutions. Enties 6 4 -z (befoe global) 1.6 (mm) Enties 3 Befoe global alignment -φ (befoe global).34 (mm) Residual (mm) Residual (mm) Residual centeed Resolution by C Enties 6 -z (afte global) 1.5 (mm) Enties 4 -φ (afte global).7 (mm) Residual (mm) 1 Afte global alignment Residual (mm) ACA5, ESY, Zeuthen 1

13 Intenal alignment (among MV laddes) 1. efine χ fo each ladde. (3 χ with 6 OF each). Loop ove all events 1. Loop ove all tacks in the event 1. Loop ove all hits in the tack 1. Find the ladde whee the hit esides. Exclude all hits in the ladde. 3. Refit the tack with all othe hits. 4. Calculate the intesection of the efitted tack and the ladde. 5. Calculate the esidual between the hit and the intesection. 6. Update the matix (M) and the vecto (V) using the tack diection, intesection and the esidual. 3. Once M and V ae calculated using all hits/tacks, calculate the alignment paametes. efitted tack (no geomety of the ladde to be aligned) ACA5, ESY, Zeuthen 13

14 ACA5, ESY, Zeuthen 14 Expession fo intenal alignment (-measuement) ( ) R R R a z p p z z p p p p Z Y Z Y y x y x y x x x 1 Ingedients fo the χ minimization the esidual of the hit to the tack with the stating geomety. the hit position on the senso and the diection of the tack at the intesection. a v x z 1,, a v aa M v M

15 tanslation otation /N dof χ (µm) R (mad) Convegence afte iteations Iteations Iteations 1-1 (µm) Y R Y (mad) Impovement of χ Iteations -.5 befoe afte along along Y along Z Z (µm) R Z (mad) Iteations aound aound Y aound Z afte each iteation (single ladde). (Simila convegences seen fo all laddes) Computation time : ~1 hous on a single CPU (Intel EON.4 GHz) Good convegence afte a few iteations. < 5 µm <.1 mad Size of the alignment ~< 1 µm ~< 1 mad Iteations Iteations Iteations ACA5, ESY, Zeuthen 15

16 Effect on esidual distibutions Enties -z (befoe intenal) 11 (µm) Enties 3 -φ (befoe intenal) 99 (µm) Befoe intenal alignment Residual (µm) Residual (µm) Residual centeed Width became naow Enties 6 -z (afte intenal) 47 (µm) Enties 4 -φ (afte intenal) 6 (µm) Afte intenal alignment 4 z 47 µ m 6 µ m φ Residual (µm) Residual (µm) ACA5, ESY, Zeuthen 16

17 Residual offsets afte alignemnt Residual offset (µm) 4 -z Ladde numbe Residual offset (µm) 4 -φ - Residual offsets of centeed aound zeo, within 1 µm. Both -z and -φ diections Ladde numbe ACA5, ESY, Zeuthen 17

18 Effect on impact paamete esolution H vs. p y (mm) δ.1.1 x esign:.3/p.97 (mm). Aligned:.151/p.53 (mm) (GeV) p Impovement ( H ): µm ACA5, ESY, Zeuthen 18

19 Summay & Conclusion Alignment of the ZEUS bael MV using cosmic tacks. Local χ minimization with linea appoximation. Good convegence obseved afte a few iteations to < 5 μm. Alignment pecision estimated fom the esidual offset <1 μm. Impact paamete esolution : 1 μm 5 μm. ACA5, ESY, Zeuthen 19

20 Backup slides ACA5, ESY, Zeuthen

21 Residual offsets on individual sensos (afte alignemnt) Residual offset (µm) 1-1 -z Enties 1 5 -z Residual offset (µm) z senso numbe 1-1 -φ Enties Residual offset (µm) 6 4 -φ φ senso numbe Residual offset (µm) Residual offsets of centeed aound zeo. (sensos with moe than 5 hits) Offsets moe spead aound zeo than in the whole ladde.(~1 µm) Non-unifom distibution of hits in sensos. Some sensos not well constained. Residual mis-alignment of sensos in laddes. ACA5, ESY, Zeuthen 1

22 Residual offsets on individual sensos (no alignemnt) Residual offset (µm) 1-1 -z Enties 1 5 -z Residual offset (µm) z senso numbe 1-1 -φ Enties Residual offset (µm) φ φ senso numbe Residual offset (µm) Befoe the intenal alignment, esiduals not centeed at zeo. Sensos scatteed aound within ±1 µm especially fo -z sensos. ACA5, ESY, Zeuthen