Towards the edge measurement

Towards the edge Towards the edge measurementmeasurement

TOTEM Collaboration MeetingTOTEM Collaboration Meeting

15-16 Feb. 200515-16 Feb. 2005

Hubert NiewiadomskiHubert NiewiadomskiTOTEM, CERNTOTEM, CERN

Brunel UniversityBrunel University

Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC

X5 Data currently available for trackingX5 Data currently available for tracking

Reference potsReference pots Test potsTest pots

Strips in U Strips in U directiondirection

Top ref. pot: 1 det.Top ref. pot: 1 det.

Bottom ref. pot: 3 dets.Bottom ref. pot: 3 dets.

Botom test pot: 1 detBotom test pot: 1 det

Strips in V Strips in V directiondirection

Top ref. pot: 2 dets.Top ref. pot: 2 dets.

Bottom ref. pot: 1 detBottom ref. pot: 1 det

Top test pot: 2 dets.Top test pot: 2 dets.

Botom test pot: 1 detBotom test pot: 1 det

Run Run 35563556 423k423k Run Run 35593559 111k111k Run Run 35613561 163k163k Run Run 35356565 255k255k Run 3611Run 3611 152k152k Run 3668Run 3668 256k256k

1.4 M1.4 M

Available detectors:Available detectors:

Main available runs and corresponding events:Main available runs and corresponding events:


Top reference RP

Bottom reference RP

mm

mm

mm

mm

Bottom test RP

Top test RP

Scintillator

Detector overlappingsDetector overlappings

5.5

mm


The tracksThe tracks 80 % events suitable for tracking80 % events suitable for tracking Tracks are fitted separately in U and V direction with Tracks are fitted separately in U and V direction with

clusters from references detectorsclusters from references detectors 15 % - 18 % of tracks (depending on run and cut) go 15 % - 18 % of tracks (depending on run and cut) go

through the overlapping region of test detectorsthrough the overlapping region of test detectors Frequencies of hits for tracking (always at least 3 hits Frequencies of hits for tracking (always at least 3 hits

for U and V directions of reference pots required) :for U and V directions of reference pots required) :

Reference potsReference pots Test potsTest pots

U direction U direction detectorsdetectors

Bot. RP, det. 1: 98%Bot. RP, det. 1: 98%



Top RP, det. 1: 100%Top RP, det. 1: 100%


V direction V direction detectorsdetectors








Example tracks, run 3556Example tracks, run 3556

Z position, [mm] Z position, [mm]

U d

irec

tio

n,

[str

ips]

V d

irec

tio

n,

[str

ips]

Track 1, run 3556Track 1, run 3556Track U projection Track V projection

Z position, [mm] Z position, [mm]

U d

irec

tio

n,

[str

ips]

V d

irec

tio

n,

[str

ips]

Track 2, run 3556Track 2, run 3556Track U projection Track V projection


v1

v2

}E{ 12, 12vvvv

2 and 1 det. of hits ofposition - , 21 vv

beam

v1 v2

u1

1

1,,

)(12

12 u

uvvvv

α 2,1

beam

Software alignment (1)Software alignment (1) Shifts:Shifts: Rotations:Rotations:

In alignment procedures instead of dets. In alignment procedures instead of dets. uu11 and and vv11 the corresponding values from the corresponding values from tracking are used.tracking are used.

Shifts and rotations are then calculated with respect to the tracking reference system.Shifts and rotations are then calculated with respect to the tracking reference system.


Software alignment (2)Software alignment (2) Example residual distribution and profile of top ref. 6 det.Example residual distribution and profile of top ref. 6 det.

u fitted, top_ref_6 [strips]

Δv

top

ref

6 [

str

ips

]

u fitted, top_ref_6 [strips]

Δv t

op

ref

6 [

str

ips

]

vvreftopreftop top ref bazvv 6. 6. 6.

direction for parameters tracking- ,

applied), correctionshift (only

det., 6 ref. in topcluster ofposition - 6.

vba

v

vv

reftopmrad003.0859.2

.

6. ,6.

systemref

top refvv u

vmref. systereftop


Aligning procedureAligning procedure Input data resolutions:Input data resolutions:

Aligning is an iterative process, still in progressAligning is an iterative process, still in progress Steps of aligning procedure:Steps of aligning procedure:

a) Transformations of signs axes of coordinate systems (bottom pots were upsite down)

b) Application of rough u and v shifts (from detector correlations)

c) Tracking, calculation of residual and Chi-Squared distributions

d) Calculation of improvements to the shifts and rotations

e) Application of shifts and rotation corrections(rotations are performed around the center of overlapping area of reference detectors, one coordinate is taken from the detector and the other form a fitted track)

f) Go to c)

mmz 1 )1(

mmOspreadanglebeamz (positions inside RP with accuracy of

0.1mm, distances between assemblies will be measured more precisely),

stripsmm

vu 29.01912

66, In fact better because of charge sharing –

multiple strip cluster position weighted by signal


Aligning procedureAligning procedureBehaviour of residualsBehaviour of residuals

Res

idu

al [

stri

p]

Perpendicular direction [strip]

Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Res

idu

al [

stri

p]


Shifts and rotations correction


Some alignment outcomesSome alignment outcomes Relative u and v shiftsRelative u and v shifts Relative rotations between detector planes of strips Relative rotations between detector planes of strips

in the same directionin the same direction

Beam angular spreadBeam angular spread Improvenemt of Chi-Squared Improvenemt of Chi-Squared distributionsdistributions


Further stepsFurther steps Some further tuning interations of software Some further tuning interations of software

alignmentalignment Studies on ortogonality of u and v Studies on ortogonality of u and v

coordinatescoordinates Analysis of errorsand expected residual Analysis of errorsand expected residual

distributionsdistributions Investigating the influence of charge Investigating the influence of charge

sharing on detectors resolution (currently sharing on detectors resolution (currently the positon of a multistrip cluster is the positon of a multistrip cluster is weighted by signal of the strips)weighted by signal of the strips)

Measurements of the vacuum pipe Measurements of the vacuum pipe assemblyassembly


Jitterring problemsJitterring problems Serial data stream from Serial data stream from

detectors shouid be detectors shouid be synchronized up to one synchronized up to one clock at FED’s entryclock at FED’s entry

Some problems with Some problems with hybrids’ PLLs caused hybrids’ PLLs caused sometimes shifts of sometimes shifts of several clock cycles in the several clock cycles in the serial data streamserial data stream

The problem appeared The problem appeared both in SPS and in X5 test both in SPS and in X5 test beamsbeams

Correction of data is Correction of data is complex since data complex since data stream headers are not stream headers are not available in new FEDsavailable in new FEDs

Jitterring detectors Jitterring detectors (without correction) are (without correction) are useless for analysisuseless for analysis

Each fiber stream Each fiber stream containes 2 containes 2 interleaved interleaved streams from APVsstreams from APVs

APV channels are APV channels are read out in a read out in a nonsequential way nonsequential way (several levels of (several levels of multiplexers in multiplexers in readout)readout)


Expected start of data stream

Data transmision delayed by 1 clock

Stream byte noStream byte no

Str

eam

val

ues

Str

eam

val

ues

Run 3037, bottom RP, 2nd cardRun 3037, bottom RP, 2nd card

Correct start of data stream

Stream byte no

The 2 fibers of a jitterring hybrid The 2 fibers of a jitterring hybrid generally jitter in parallel, but not generally jitter in parallel, but not alwaysalways


Feasibilty and neccessity of Feasibilty and neccessity of jitterring correctionjitterring correction

X5:X5: Jitterring correction would Jitterring correction would

increase the precision of increase the precision of detector edge studies (up to detector edge studies (up to 4 more detectors in tracking, 4 more detectors in tracking, depending on the run)depending on the run)

Correction of several clock Correction of several clock shifts is probably possible shifts is probably possible with statistical methods with statistical methods (tests in progress), but (tests in progress), but complexcomplex

We don’t know what kind of We don’t know what kind of data the jitterring detectors data the jitterring detectors can provide us with (without can provide us with (without good pedestals clusters are good pedestals clusters are not visible)not visible)

SPS data:SPS data: Jitterring correction is Jitterring correction is

needed for tracking on SPS needed for tracking on SPS runsruns

Correction possible basing Correction possible basing on available headers of data on available headers of data streams, quite complexstreams, quite complex

Strips of det. 6

Str

ips

of

de

t. 2

Correlation of 2 paralell jit. dets.Correlation of 2 paralell jit. dets.


Statistical jitterring correction algorithmStatistical jitterring correction algorithm Periodic structure of fiber data stream, can be used for Periodic structure of fiber data stream, can be used for

resynchronization of the order of several clock cyclesresynchronization of the order of several clock cycles

1.1. Application of discrete highpass filter Application of discrete highpass filter to data buffers in order to emphasize to data buffers in order to emphasize the periodic structure of the signal:the periodic structure of the signal:

2.2. Distributions of differences Distributions of differences between corresponding bytes of between corresponding bytes of such signals become narrowest such signals become narrowest if no shift is present, which if no shift is present, which allows to determine the shiftallows to determine the shift

RMS = 33.18RMS = 33.18

Buffers shifted by 1 clockBuffers shifted by 1 clock

RMS = 8.23RMS = 8.23

Buffers not shiftedBuffers not shifted


TestsTests

Tests on not jitterring detectors (runs 3556, Tests on not jitterring detectors (runs 3556, 3668) shown that error rate of shift 3668) shown that error rate of shift determination of the order of 10determination of the order of 10-4-4 is is probably achievableprobably achievable

Tests with jitterring detectors revealed Tests with jitterring detectors revealed jitterring shifts of up to jitterring shifts of up to ±±2 clocks2 clocks

Tests of event correlations between Tests of event correlations between jitterring and nonjitterring detectors are jitterring and nonjitterring detectors are neededneeded

Towards the edge measurement

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