a recoil detector to measure hard exclusive reaction at hermes experiment roberto francisco perez...

A recoil detector to measurehard exclusive reaction at HERMES experiment

A recoil detector to measurehard exclusive reaction at HERMES experiment

Roberto Francisco

Perez Benito

Hyytiälä, 25 -30 September 2006

Roberto Francisco

Perez Benito


Lecture Week on The Physics of Hadrons

and Ultrarelativistic Heavy Ion Collisions

Lecture Week on The Physics of Hadrons

and Ultrarelativistic Heavy Ion Collisions

OutlineOutline

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


• Motivation– DESY & HERA– Spin of the Nucleon

• DVCS & BH• HERMES

– End of polarized gaz Target– Hermes Recoil Detector

• Design Requirement• Recoil Detector

– Silicon Strip Detector (SSD)– Scintillating Fiber Tracker (SFT) – Photon Detector (PD)

• SFT Performance

DESY @ Hamburg - GermanyDESY @ Hamburg - Germany

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


HERA @ DESYHERA @ DESY

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Spin of the NucleonSpin of the Nucleon

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Naïve parton modelNaïve parton model

43 vu 1

3 vdBUTBUT

1989 EMC measured1989 EMC measured = 0.120 0.094 0.138= 0.120 0.094 0.138± ±

Spin PuzzleSpin Puzzle

Unpolarised structure fct.Unpolarised structure fct.

Gluons are important !Gluons are important !

Sea quarks Sea quarks qqss

GG

Full description of JFull description of Jqq and J and Jgg

needsneedsorbital angular momentumorbital angular momentum

1 1( )

2 2 v vu d 1 1

( )2 2 v gsv qLd LGqu

1 1( )

2 2 v svu q Gd

( ) s su d u d s s

The hunt for LThe hunt for L

Study of hard Study of hard exclusive processesexclusive processes leads to leads toa new class of PDFsa new class of PDFs

qq

GGeneralized eneralized PParton arton DDistributionsistributions , , ,

qqq q HH EE

exclusive:exclusive: all products of the reaction are detected all products of the reaction are detected missing energy (missing energy (E) and missing Mass (ME) and missing Mass (Mxx) = 0) = 0

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


possible access topossible access toorbital angular momentumorbital angular momentum

1

1 0

1

2q

qq

t

HJ Exdx

1

2q qLJ

from DIS:from DIS:HERMES ~0.3HERMES ~0.3

isolate isolate BH-DVCS interferenceBH-DVCS interference term non-zero azimuthal asymmetries term non-zero azimuthal asymmetries

DVCSDVCS Bethe-Heitler (BH)Bethe-Heitler (BH)

HERMES kinematics:HERMES kinematics:BH c.s. >> DVCS c.s.BH c.s. >> DVCS c.s.

DVCS & BHDVCS & BH

p + p +

two experimentally undistinguishable processes:two experimentally undistinguishable processes:

* 2 2*~ | | | |BH DVCS DVC BS HB DVCSHd

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


HERMES HERMES

•The Missing mass resolution of the Hermes is not sufficient to identify exclusive events individually and separate to them

End of Polarized targets at HERMESEnd of Polarized targets at HERMESDVCS exclusivity by missing mass MDVCS exclusivity by missing mass Mxx

Improve ExclusivityImprove Exclusivity

Detect recoiling protonDetect recoiling protonmodify target regionmodify target region

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Detector to measure recoiling protonDetector to measure recoiling proton

detection of the recoiling protondetection of the recoiling proton

P: 135 – 1500 MeV/cP: 135 – 1500 MeV/c

76% 76% acceptance acceptance

/p PID via dE/dx/p PID via dE/dx

background suppressionbackground suppression

semi-incl.: 5 %semi-incl.: 5 %associated: 11% associated: 11%

improved t-resolutionimproved t-resolution

study kinematical study kinematical dependencesdependences

data taking 2006/2007data taking 2006/2007

HERMES Recoil DetectorHERMES Recoil Detector

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Build by DESY, Erlangen, Ferrara, Frascati,Build by DESY, Erlangen, Ferrara, Frascati,Gent, Gent, GießenGießen and Glasgow and Glasgow

Silicon Strip Detector (SSD) Silicon Strip Detector (SSD)

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Scintillating Fiber Tracker (SFT)Scintillating Fiber Tracker (SFT)

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


p-measurement 300-1500 MeV/c π/p PID from dE/dx for p<700 MeV/c 2 cylinders of 2x2 layers, 10° stereo angle 1mm Kuraray fibers, mirrored ends and double cladding PMT Hamamatsu H7546B

5120 channels total full Ф coverage

Remove edge fibers

42 (36) inner (outer) modules

1318 (1320) fibers in inner parallel (stereo) sub-barrel

2198 (2180) fibers in outer parallel (stereo) sub-barrel

Scintillating Fiber Tracker (SFT)Scintillating Fiber Tracker (SFT) Space point reconstruction

Parallel & stereo configuration High detection efficiency

Double fiber layer per sub-barrel MIP signal separated from noise

Spacial resolution σ V Multiple scattering limits resolution

1mm fiber sufficient Minimise suport structure

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Photon DetectorPhoton Detector

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Detect f ´s from ∆ resonnance

Reconstruction if both decay f ´s detected

Contribute to the pion/proton PID separation (together with SFT) for p> 600 MeV/c

MIP signal are far away from pedestal

multilayer construction with parallel and stereo strips

Cosmic trigger generator


Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


6 layer (inside out) 6mm Tungsten A layer: 60 strips along z axis 3mm Tungsten B layer: 44 strips -45° stereo angle 3mm Tungsten C layer: 44 strips +45° stereo angle

2 WLS on both side of each strips

radius 20cm dimensions of strips 2cm x 1.1cm x 28cm

Recoil Detector - installationRecoil Detector - installation

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT Current StatusSFT Current Status

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Clear hit in SFT with low background

of course subject to optimization but nevertheless the SFT detector worked from the beginning as expected

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT CallibrationSFT Callibration

Callibration data (blue LED pulser) from Gießen test was re-fitted with Poisson & Gauß fit

Gain (extracted from fit) vs. high voltage

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT Origins of CrosstalkSFT Origins of Crosstalk

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT Crosstalk CorrectionSFT Crosstalk Correction Tracklet Algorithm: combine

signal in adjacent fibers into one cluster.

Cluster Algorithm: search for the hightest signal, then add the signal of the PMT channels left, right, up and down.

SFT Crosstalk & Clustering SFT Crosstalk & Clustering

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT perfect agreement between MC and data SFT perfect agreement between MC and data

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


Digitization carfully improved

reasonable energy reponse of the SFT

MC and cosmics data agree perfectly

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SFT Gain Correction & TDC cut SFT Gain Correction & TDC cut

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


More positive More positive

Summary and Outlook Summary and Outlook

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


• Silicon – Hardware not yet in perfect shape– Some more time needed– Need to understand data

• Scintillating Fiber Tracker– Fine calibration – Crosstalk correction and Clustring– π/p PID from dE/dx

• Photon Detector – Comparision with MC for energy

deposition need more investigation– Crosstalk in PMT

ENDEND

Extra Extra

SFT CrosstalkSFT Crosstalk

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


h1,2,3,4

h

=

=+h2 h3 h4h1 ++h +

+h2 h3 h4h1 ++h +

h1,2,3,4

+h2 h3 h4h1 ++

Extra Extra

Extra Extra

Extra

Extra Extra

Design RequirementDesign Requirement

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


SSD Current Status SSD Current Status

Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


• SFT only track Prediction for Hits in SSD SFT integrates over several bunches TDC cut

•Each hit used in track needs to have one correct timestamp

•Good tool for alignment

• P and N side different gain.

Signal on N side cut off

Hardward not yet in perfect shape.


Roberto Francisco

Perez Benito


Roberto Francisco

Perez Benito


• Require exactly 1 lepton in Spectrometer with cut on momentum (and coplanarity)

• Require lepton momentum in [25.5-27.6552](GeV/c)

• In addition proton momentum > 1.2 GeV/c

• Fine calibration

a recoil detector to measure hard exclusive reaction at hermes experiment roberto francisco perez...

Documents

dimensions of strips

subbarrelmip signal

z axis3mm tungsten b

exclusive events

inner outer modules1318

measurehard exclusive

undistinguishable processes

mevcp pid