The SVT Physics and Future Lifetime

As impressive as the.. other.. editions are, they seem a little tame compared to the SVT. In fact, this little honey should be able to run with some pretty tall dogs with pretty fancy pedigrees ......for the truly young and restless, the SVT is something special. (New Car Test Drive.com ( Ford SVT Contour)) STAR Near Term Upgrades Workshop Helen Caines - Yale University June 2004

Performance in run IV

Ru n IV 35.0E+06 30.0E+06 25.0E+06 20.0E+06 15.0E+06 10.0E+06 TPC TPC+SVT 50.0E+05 00.0E-01 Cen tral Min Bias Low Mid High 62 GeV pp 87.6% Lost MinBias were in Jan.

48 % those from 25 th -31 st

Trigge r Type SVT Pre se n ce

Ce n tra l Min Bia s Lo w 98.6% 77.9% 87.7% Mid High 62 Ge V p p 91.9% 89.3% 95.1% 81.8% Down Feb. 7 th , 8 th , and 9 Missed ~2.51 M evts. th Problems with TCD Position Helen Caines – June 2004

2

Detector Status

♦ Averaged Over the Run: ~85% of the SVT is good ♦ Three Half-Ladders (~1.5% each ): L07B3, L11B3, & L12B2 ♦ ♦ ♦ L07B3: no HV above -350 V L11B3: lost ¼ during '02, rest during shutdown L12B2: exhibiting abnormally high noise ♦ RDOE7 (~4.2%) Lost due to electronics failure, March 6 th ♦ RDOW3 & RDOW4 down, rectifier failure in PS, March 29 th Recovered April 2 nd ♦ Typical fluctuation ~3% Helen Caines – June 2004

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“Bad” channels history

Bad = dead or noisy 1.

2.

3.

4.

5.

6.

7.

8.

9.

36 Ladders built Ended Jan 2001 Ladders mounted on end-rings & installed cone Run II Au-Au Run II p-p Shut down (leak repair) Run III commissioning Run III d-Au and p-p Start Run IV End Run IV Ended March 2001 Aug 2001 - Nov 2001 Dec 2001 - Jan 2002 Feb 2002 - Sept 2002 Oct 2002 - Dec 2002 Jan 2003 - May 2003 ~12.7% Jan 2004 May 2004 < 1% ~3.7 % ~10.5% ~13.6% ~15.9% Note: % doesn’t show those used in various run but those intrinsically damaged.

i.e. Read Out Boxes failed but were repaired during the run. Therefore a slightly lower operational % used than shown here.

Seems that when SVT left alone number of bad channels stays stable Helen Caines – June 2004

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Detector lifetime

Future difficult to predict: ♦ This year a maximum of 3% bad channels added ♦ Extrapolating 5 years  70% alive BUT With minimal handling and disconnecting from RDO’s things may not be that bad ♦ Most failures seem to be “grouped” ♦ one sca out of 5 fails ♦ one analog driver is bad ♦ bad/broken connector from detector to rdo ♦ bad adc in rdo ♦ Not much trend of single channel failures Helen Caines – June 2004

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Helen Caines – June 2004

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♦ ♦ ♦

Calibration Techniques

♦ Gain Hybrid to hybrid and within hybrid.

1.

Look at hits placed on tracks with given mtm and average charge should be the same. Scale “gain” to force them to be.

♦ Drift Velocity Hybrid to Hybrid and within hybrid.

1.

Look at start and stop of hits – Know drift == 3cm, calc V dhybrid 2.

3.

Use laser spots to monitor temp. variation event by event.

.

Use bench measurements to account of non-linearity of drift.

4.

Use bench measurements to account for temp. profile across anodes.

Alignment ♦ Global, Barrel, Ladder, Wafer.

1.

Project TPC tracks to SVT hits, calc. residuals.

2.

3.

Refit TPC tracks with SVT hits, calc. residuals.

Refit matched SVT hits and primary vertex, calc. residuals.

♦ Deviations from means of zero give shifts.

♦ Try shifts and rotations to minimize offsets.

♦ Some offsets due to TPC distortions not ONLY SVT.

Helen Caines – June 2004

7

Drift velocity from hits

Fitting First & Last Points Charge Injectors 3 cm Mean distortion is a few 100 m m Helen Caines – June 2004

8

Polynomial drift representatopm

9 th order polynomial Difference from fit Account for focusing region Difference from fit RMS=17.9

µm Helen Caines – June 2004

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anode

Hit position reproducibility

spot 1 σ=4.4μm spot 2 σ=3.0μm 3 laser spots 2 spots

are at: hybrid=1, layer=6, ladder=15, wafer=7

1 spot

is at: hybrid=2, layer=6, ladder=7, wafer=1

anode σ=5.985 μm Laboratory laser tests: anode direction

: σ=6 μm Similar resolution in STAR as on bench ♦ SVT proposal Helen Caines – June 2004

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Time variations of laser spot positions

slow-control temperature measurement drift distance of spot 1

75 74.5

74 73.5

73 72.5

72 9:57 10:04 10:12

Time

10:19

Temperature oscillations have a period of ~2.5 min Temperature oscillation is ~1 o c peak-to-peak Position peak-to-peak change is ~70 μm Helen Caines – June 2004

10:26

11

10:33

spot 1 spot 2

Time variations of laser spot

water cooling



time variations of laser spot positions

spot positions change in phase

BUT

spots behave differently after SVT is switched on and gets stabilized (~ 1 hour !) spot 1: 80 microns spot 2: stable spot 4: 300 microns

spot 4

Helen Caines – June 2004 Can we calibrate out the burn in?

12

Drift velocity calibration

♦ Use 2 spots on one wafer d 1 – d 2 = d 12 = v(t 1 -t 2 ) ♦ Distance is in fact the same so apparent change is due to D v ♦ Using and can calc. D v event-by-event

Time difference of spot 1 and 2 Time variations of drift velocity

Helen Caines – June 2004

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Corrected laser spot positions

black before, red after the drift velocity calibration before: σ=(22.1

± 0.2)μm after: σ=(10.0

± 0.1)μm ♦ Get delta function for spots used in calc – phew!

Laser spot on other wafer improves by factor 2

time direction

: σ= (5 – 23) μm (depending on the position)

(NIM A439, 2000; SVT proposal)

Helen Caines – June 2004

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Anode temperature profile

● 40 ns/TB = ~270 µm/TB ● ~150 m m max shift Wafer width ♦ ♦ Temperature gradient across wafers must be taken into account Due to resistor chains at edges Have bench measurement for each hybrid needs to be used Helen Caines – June 2004

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Alignment

We seek for 6 parameters that must be adjusted in order to have the SVT aligned to the TPC:  x shift  y shift  z shift  xy rotation  xz rotation  yz rotation Have to calculate for each wafer – 216 in total The Question ♦ How to disentangle and extract them without ambiguity from the data?

♦ Many approaches are possible. We are using two of them...

Helen Caines – June 2004

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The two approaches

First approach :  Calculate the “residuals” between the projections of TPC tracks and the closest SVT hit in a particular wafer.



Advantage

:  can be done immediately TPC calibration is OK (not final), even without B=0 data.



Disadvantage

:  highly dependent on TPC calibration.  the width of these “residuals” distributions and therefore the precision of the procedure is determined by the projection resolution.

Second approach:  Use only SVT hits in order to perform a self-alignment of the detector.



Advantage

:  a better precision can be achieved.  does not depend on TPC calibration.



Disadvantage

:  it is harder to disentangle the various degrees of freedom of the detector (need to use primary vertex as an external reference).

 depends on B=0 data (can take longer to get started).

Helen Caines – June 2004

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First approach: TPC track projection

Try to disentangle the 6 correction parameters in 2 classes: 

res drift

x shift, y shift and xy rotation.

 D

x



sin  

 D

y



cos  

 D

   tan  1  z shift, xz rotation and yz rotation.

Look at “residuals” from the SVT

anode direction

(global z direction); Choose tracks with dip angle close to zero ( tracks parallel to the xy plane); Study as function of z: deviations from a flat distribution centered at zero show mis-alignment They are not completely disentangled, but it works as a first approximation..

Make the alignment in steps: 1.

global alignment, i.e., one set of parameters for the whole 2.

detector; ladder by ladder alignment, i.e., a set of parameters per 3.

ladder; wafer by wafer alignment, i.e., a set of parameters per wafer.

Helen Caines – June 2004

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D

x,

D

y,

D

corrections

D

x = -0.25 mm

D

y = 0.10 mm

Matches well the survey data

res drift

 D

x



sin  

 D

y



cos Helen Caines – June 2004

D



19

First look z shifts, no corrections

♦

Only ladders at xz plane

♦

Only ladders at yz plane

No sizable correction needed Helen Caines – June 2004

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Next step ladder by ladder

♦ Look at “residuals” from the SVT

drift direction

(global x-y plane).

♦ Study them as a function of drift distance (

x local

) for each wafer.

♦ Now influence of mis-calibration (

t 0

neglected.

res drift

 D

x



sin    

local





and drift velocity) cannot be

D

y



cos    

local



 D



res drift v`



x local



v





x local



L

  0

v

is the correct drift velocity and t 0 ` is the correct time zero.

t

0  0, if t 0



L

is Ok These two equations can be used to fit the “residuals” distribution fixing the same geometrical parameters for all wafers.

Helen Caines – June 2004

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One ladder as example

D

x = -0.81 mm

D

y = 0.56 mm

Helen Caines – June 2004

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Technique works!

  Need to go ladder by ladder (36 total) checking the correction numbers and the effect of them on the “residuals”.

Still need to consider the rotation degree of freedom.

Next step is to fit each wafer separately.

wafer 1 2 3 4

D

x (

m

m) -190 -62 -34 -92

D

y (

m

m) 151 67 83 58

Helen Caines – June 2004

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Near future perspectives

Finalize first approach:  calculate D

x

, D

y

, and D  finished for inner barrel) ladder by ladder. (Just  extend it to wafer by wafer making small corrections if necessary;  calculate z shift, xz rotation and yz rotation (global, ladder by ladder and wafer by wafer - they should be small);  use B=0 data. ( Work being done now) ♦ ♦ ♦ It is a lot of work, but it depends mostly on man power.

Software is ready The whole procedure does not depend on many iterations of the reconstruction chain. Can be applied and tested without full reconstruction Helen Caines – June 2004

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Track matching efficiency

Note: Get similar tracking results with Sti

HIJING 200 GeV AuAu Prod62 GeV

Global Tracks Primary Tracks 80% 85% SVT is most efficient between PV +- 10 cm!!!

76% 83% Helen Caines – June 2004

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Track matching efficiency II

Number of EST tracks does not increase with multiplicity, an indication that there is no increase of ghost tracks .

Helen Caines – June 2004

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Identifying primary tracks

♦ Hijing ♦ Data Significant improvement in impact parameter for primary tracks Helen Caines – June 2004

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Track residuals: simulated data

♦

Dependency on the attributed hit error – simulation had 20

m

m smearing

p-p Helen Caines – June 2004

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Track Residuals

HIJING AuAu simulated data, with SVT hits position smeared by 80 m m.

Only TPC hits PV + 2 SVT hits + TPC hits PV + 2 SVT hits PV + 3 SVT hits

Anode

320 m m 120 m m 110 m m 72 m m

Drift

350 m m 120 m m 120 m m 70 m m Resolution of ~SQRT(110*72) = 90 m m Au-Au 62 GeV Average over all Barrel 2 Anode 180 m m Drift 300 m m Helen Caines – June 2004 Solution Barrel Alignment

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Track Residuals: Au+Au 62 GeV

Average over all Barrel 2 Ladder 03 Ladder 10 Anode 180 m m 84 m m 280 m m Drift 300 m m 140 m m 180 m m Solution Alignment between ladders.

Helen Caines – June 2004

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Track Residuals: Au+Au 62 GeV

Anode 180 m m Drift 300 m m Solution Average over all Barrel 2 Ladder 03 L03/wafer 48 L03/wafer 48/hybrid-02 84 m m 60 m m 60 m m 140 m m 140 m m 60 m m Ladder Alignment Wafer Alignment Alignment & drift velocity D

Z vs. Drift Distance

D

Y vs. Drift Distance

Helen Caines – June 2004

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Helen Caines – June 2004

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Physics interests

♦ Measurement of low p T (60-200 MeV/c) particles ♦ Improved reconstruction of strange baryons ♦ Reconstruction of heavy quark mesons (not going to discuss) ♦ Improvement of high p T primaries reconstruction/resolution (already shown dca improvement) Helen Caines – June 2004

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Low-p

T

yields compared to models

• Event generators unable to consistently describe low p T • HIJING overpredicts yields at low p T .

yields.

• Ratio of measured to HIJING yields averaged over low p T range: ( Y exp / Y HIJ )   0.80

 0.02

( Y exp / Y HIJ ) K  0.61

 0.02

( Y exp / Y HIJ ) p  0.183

 0.014

( Strangeness Production in PHOBOS ”,

C. Henderson, MIT,

RHIC/AGS Users’ Meeting, May 2004, BNL) Helen Caines – June 2004

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Low p

T

physics – particle yields

p-p dN/dy X : Exponential: 0.00268 +/- 0.0005

Power Law: 0.00181 +/- 0.0004

X : Exponential: 0.00270 +/- 0.0005

Power Law: 0.00178 +/- 0.0004

Distinguishing between fit models is critical to determine yields!

Helen Caines – June 2004

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Sti - efficiency and purity

♦ ♦ Clean up via normal tracking first Start with SVT and move outwards ♦ Efficiency is low but that would be OK as long as pure ♦ By removing obviously bad hits purity good Work just starting but looks promising!

Helen Caines – June 2004

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K

0 s

in Au-Au 62 GeV

K 0 s raw yield vs P T P T < 400 Mev/c

120 % improvement in lowest p T similar result seen in p-p bin Helen Caines – June 2004

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L

in Au-Au 62 GeV

P T < 800 Mev/c

40% improvement in lowest p 15% improvement for L T 100% seen in p-p for p T bin < 0.5 GeV Helen Caines – June 2004

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MSB from Au+Au-Simulation

W enhanced Hijing events W SVT+TPC Tracks: 3210 Ω’s TPC only Tracks: 2020 Ω’s

Increase of signal by 60%

Helen Caines – June 2004

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T 0

Slow simulator close to tuned

BLACK-real AuAu 200GeV GREEN- Hijing simulation time bin peak ADC ADC sum Helen Caines – June 2004

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simulated hits

Embedding Works

real data to embed into embedded data anode simulated raw data anode anode Helen Caines – June 2004 anode

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Correcting data seems OK

Preliminary test on 200 GeV dAu data

requiring 2 SVT hits on EST track

Helen Caines – June 2004 Black – TPC only Red – TPC + SVT

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SVT lifetime expectations

♦ We do not see evidence for aging or continuous channel loss therefore the limitation of the usefulness of the detector is due to the RDO.

♦ The detector can run up to a maximum DAQ rate of around 200 Hz without serious performance limitations ♦ Between 200 to 300 Hz the required SCA settling time will lead to increased noise levels and the detector requires hardware changes to the RDO.

♦ The detector can not operate above 300 Hz.

♦ The detector electronics can not be upgraded as was done in the case of the TPC.

Helen Caines – June 2004

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SVT future plans

♦ We do not anticipate to remove the detector for repair or electronics upgrades . ♦ We would like to run the detector until STAR decides to remove it due to readout speed limitations.

♦ We like to be in STAR at least until 2009 beam time.

♦ The detector is designed such that the inner layer can be removed to generate space for the APS upgrade. Helen Caines – June 2004

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