Latest news on dE/dx

P. Branchini, E. De Lucia, P. de Simone,

L. Passalacqua and V. Patera

ADC pedestals in HEPDB

HEPDB bank DPED

1. Pedestal value in ADC counts2. RMS value in ADC counts3. Packed first layer-wire of the super-cell4. Packed last layer-wire of the super-cell5. Packed FEE address

RAW2DQCE

YBOS bank DQCE

1. Packed first layer-wire of the super-cell2. Packed last layer-wire of the super-cell3. Charge measurement in ADC counts

The available code

The AC module: DCDEDX

for each reconstructed track:

• steps along the helix to find the crossed wires,• evaluates the length inside the crossed super-cell,• associates the measured charge and writes the YBOS bank DEDX

1. the CPU time used is 25% of ATFMOD2. the dimension of the DST output increases of 28%

DEDX will be a real DST bank with the different particle hypotheses for each reconstructed track

next step

YBOS bank DEDX

1. Packed address of the ADC channel 2. Packed address of the crossed wires from DHRE23. Packed address of the extrapolated crossed wires4. Drift time of the IN wire5. Drift time of the OUT wire6. Collected charge in ADC counts7. Track length8. Effective track length

• one bank for each reconstructed track• same ID of the DTFS bank of the corresponding track

for each hit associated to the track :

Fortran structure DEDX

In AC code the bank can be retrieved in a structure calling the function :

DEDX_UPK(num_dtfs,DEDX_structure)

INTEGER MAXNADC PARAMETER(MAXNADC = 5000)

TYPE DEDXStructure SEQUENCEINTEGER nADC

INTEGER first_w(MAXNADC) INTEGER last_w(MAXNADC)

INTEGER Layer(MAXNADC)INTEGER Wire1(MAXNADC)INTEGER Wire2(MAXNADC)INTEGER Wass1(MAXNADC)INTEGER Wass2(MAXNADC)REAL TrLen(MAXNADC)

REAL EffLen(MAXNADC)REAL Time1(MAXNADC)REAL Time2(MAXNADC)REAL Charge(MAXNADC)

END TYPE TYPE(DEDXStructure) DEDX

A prod2ntu version has been produced to embed the new block of data

• hits associated to reconstructed tracks with tdrift ≤ 150 ns have NO charge measurements • 30% of useful charge measurements are lost

First look at the data

• effect not present during first tests on ADC boards

• hardware check scheduled before restarting phase

The integration gate is 1.8 s effective track length evaluation

following equal time contours

Red: effective charge collection area Blue: total charge collection area

geom

etric le

ngth

eff. l

engt

h

Q / effective track lengthQ / geometric track length

Celle 3X3 Celle 2X2

Charge vs drift time distributions

Bhabha scattering3 body decays

kaons

K, K0

The dE/dx scenario

Bethe-Block calibration

Q/L vs log(

using appropriate mass hypothesis in the various momentum ranges

Resolution vs Number of samples

electrons

pions

0.5xN-0.5

0.4xN-0.33

to reach 5% @ N=50of the prototypeswe need to addanother 5% effect !?!

Stronger effecton the pions

(0.052 +0.052)1/2(50)1/2/N1/2

7%

tdrift < 800 ns

Raw s-t relations

800 ns

1 mm spread

The effect derives from the resolution on the effective track length

A rough estimate of the uncertainty is 1 mm/3 cm 3%

Nevertheless what can we do for 3 body decays at the present stage? (p < 150 MeV/c)

(ele)(ele))Q(Q

Q

EXPEMEAS

σ

requiring K decay vtx

Clear electron peak in the distribution

mainly3 charged pions

j

jP/)PP(

j

je P/P

Using the probabilities of being electron, pion muon, clean samples of electrons and pions can be selected

electrons

pions

muons

requiring K decay vtx

no K decay vtx

Clean electron sample requiring: 50.P/Pj

je

20.P/)PP(j

j

useful sample tostudy systematic effectsassociated to PID from time of flight for Ke3

p (MeV/c)

(ele)(ele))Q(Q

Q

EXPEMEAS

σ

no K decay vtx

Solutions under study to improve actual situation:

• debugging of hardware settings as soon as we restart • evaluation of the effective track length using fine s-t relations

pions

muons

)())(Q(Q

Q

EXPEMEAS

σ

How is the distribution of Nsamples affected by the cut on drift time?

Nsamples

without the cut

with the cut 150ns < tdrift < 800 ns