HEP Tel Aviv University

HEP Tel Aviv University

LuminosityMeasurement using

BHABHA events

Ronen Ingbir

MDI

SLAC

Lumical - A Future Linear Collider detector

Tel Aviv University HEP experimental Group

ΔE~0.31√E

)(54~)( rade

RL

Cracow

Strip design


Pad design

0.34 cm Tungsten

0.31 cm Silicon

Cell Size1.3cm*2cm>1.3cm*6cm<~1 Radiation

length~1 Radius Moliere


15 cylinders * 24 sectors * 30 rings = 10800 cells

RL

8 cm

28 cm

6.10 m



Reconstruction Algorithm

)]}ln([,0max{T

ii E

EconstW

i

ii

EEX

X

i

ii

WWX

X

Events Num.

)(radgenrec

)(radgenrec

)(radgen

We explored two reconstruction algorithms:

The log. weight fun. was designed to reduce steps in a granulated detector :

1. Selection of significant cells.

2. Log. smoothing.

Log. weight.

E weight.


T.C Awes et al. Nucl. Inst. Meth. A311 (1992) 130.


Logarithmic Constant

Constant value

Constant value

)]}ln([,0max{T

ii E

EconstW

After selecting:

We explored a more systematic approach.

The first step is finding the best constant to use under two criteria:

1. Best resolution.

2. Minimum bias.

400 GeV

))(_( radmean genrec

))(( rad



Energy dependent constant

)]}ln()([,0max{T

ibeami E

EEconstW

The goal is to find a global weight function.

Is the the log. weight constant really a constant ?

Constant value



Shower reconstruction

Num

. of C

ells

Num

. of S

ecto

rs

Num

. of C

ylin

d ers

Ene

rgy

port

ion

(%)

En>90%

)(rad )(rad

)(rad)(rad

What happens when we select the best log. weight constant ?

Shower size

Log. Weight Selection

Most of the information is in the selected cells.


HEP Tel Aviv UniversityLumical - A Future Linear Collider detector

Magnetic field


Background studiesBHWIDE + CIRCE



33 mrad

Geometric acceptance

Energy Resolution )( GeV

)(rad

Out

In

)(rad

Eout-EinEout+EinP=

3 cylinders

2 cylinders

1 cylinders



Left-Right balance RLSimulation distribution

Distribution after acceptance and energy balance selection

Right side detector signal

Lef

t sid

e de

tect

or si

gnal Right signal - Left signal

)(21 rad

(deg)21



Energy resolution

Ntuple No cuts

With cuts

Pure electrons

31% 29%

Bhabha

42% 24%

Bhabha + Beamstrahlung

45% 24%

Bhabha + Beamstrahlung + Beam spread (0.05%)

46% 25%

Bhabha + Beamstrahlung +Beam spread (0.5%)

49% 29%



Angular resolution



‘Pure’ electrons simulation Bhabha+Beam+BS(5e-4)

)(radgenrec

Bias study

44 103.1107.5


Real life algorithm

Working with both sides of the detector and looking at the difference between the reconstructed properties:

(In real life we don’t have generated properties)

2new

Dense0.156e-3Regular0.137e-3

Dense, 35%

Regular, 27%

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Ang

ular

reso

lutio

n(ra

d)E

nerg

y re

solu

tion

(GeV

)^0.

5

RegularDense


0.34 cm Tungsten

0.31 cm Silicon

0.55 cm Tungsten

0.1 cm Silicon

Dense design


30 radiation length detector47 radiation length detector

Z (cm)

Detector Signal

0.8cm

1.1cm

Moliere radius & Radiation length


)(rad

Energy Resolution )( GeV

)(rad

Events

New geometric acceptance


Optimization


Margins in between cells

Energy resolution Polar resolution


Our basic detector is designed with

30 rings * 24 sectors * 15 cylinders = 10,800 channels

Do we use these channels in the most effective way?

Maximum peak shower design

30 rings 15 cylinders

20 cylinders

10 cylinders

24 sectors * 15 rings * (10 cylinders + 20 cylinders) = 10,800 channels

4 rings 15 rings 11 rings

10 cylinders


Maximum peak shower design

Basic Design

Angular resolution improvement

without changing the number of

channels

Other properties remain the same

))(_( radmean genrec

))(( rad

Constant value

Constant value

Polar reconstruction

0.11e-3 rad0.13e-3 rad


High Statistics MC

)),(( N

NLL

)(rad)(rad

min

*2

LL

BHWIDE + fast detector simulation


‘Real physics’ MC + digitization + elec. noise + New max peak design + Margins

Final optimization

Pure electron MC Detector

propertiesEvents

selection‘Real

physics’ MCBhabha + Beamstrahlung

+ Beamspread

R&D status & future steps

))(,,),(( EENN

LL High statistics MC

410 N

N

Luminosity with a crossing angle

Luminosity with polarised beams (Gideon Alexander)


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