J.E. Garcia RTN – December 03

PHD WorkPHD Work

SCT beam test analysis:Tracking efficiency, noise occupancy, collected charge, S/N but also several studies: tracking with standalone SCT, dependencies on incidence angle, studies with LHC-like bunch structuring…

Light tight, thermally insulating box

Telescopes

180 GeV pion Beam

Telescopes

Scintillator Trigger

Modules inside the beam test box.

SetupSetup 2

SCT Beam test results

Typical SCT beam test setup with different types of modules

J. E. Garcia RTN – December 03

Variation of efficiency and noise occupancy with comparator threshold. Horizontal lines are the ATLAS specifications.

• After 10 years the SCT will receive up to 2·1014 neq/cm2. Radiation causes damage on the module.

– Radiation creates defects – Type inversion – Electronics noise and leakage current increase

• Resolution is measured. SCT modules are almost single-strip. The detector pitch is 80 m in order to avoid charge sharing and preserve a good resolution.

Beam test studiesBeam test studies 3

SCT Beam test results

~ 23 m

J. E. Garcia RTN – December 03

• The Lorentz angle has been measured using a 1.56 T magnet and different incidence angles. The most sensitive parameter to these changes is the cluster size

L = 3.3 º 0.3 º (at 150 V)

Beam test… (II)Beam test… (II) 4

SCT Beam test results

• Signal to noise ratio for the SCT modules is 14.

• The median charge observed on binary SCT prototypes is around 3.4 0.2 fC

S-Curve

J. E. Garcia RTN – December 03

The pulse shape can be reconstructed from beam test data and compared with the theoretical response of the shaper

• For reconstructing tracks only the position measurements of the irradiated SCT modules are used. The beam telescope is only read out for comparison. Example of a reconstructed event

SCT ModulesTelescope

Tracking studyTracking study 5

SCT Beam test resultsJ. E. Garcia RTN – December 03

effic

ienc

y• The tracking efficiency depends on threshold. The maximum efficiency is 97 % obtained at a threshold of 1.2 fC for a bias over 450 V.

• Fake rate is kept below 10-3 independent of the bias voltage on the detector.

J.E. Garcia RTN – December 03

PHD WorkPHD Work

SCT beam test analysis:Tracking efficiency, noise occupancy, collected charge, S/N but also several studies: tracking with standalone SCT, dependencies on incidence angle, studies with LHC-like bunch structuring…

Little Higgs Searches:Capability of the ATLAS detector to find particles predicted by the Little Higgs Models. In particular new gauge bosons in the channels: WH W H and ZH Z H

Particle SpectrumParticle Spectrum

Little Higgs Searches

7

0,+,++

WH , ZH

T

AH1 TeV

Z ,Wh

t

M

scalar sector gauge sector

topsector

v’ ’ 1

new couplings

J. E. Garcia RTN – December 03

Littlest Higgs modelSU(5) SO(5)Gauge sector [SU2U1]2

Only 1 Higgs doubletOnly 1 Higgs doublet

• Arkani-Hamed et al., JHEP 207 (2002) 34

Phenomenology

• Han et al., Phys. Rev. D67 (2003) 95004• Burdman, Perelstein, Pierce,hep-ph/0212228

Strategies at LHC 8

q

W

b T

q’

q’

q1

W+

q2

q’

W+

1

2

++q

q

ZH

++++ TT ZH

VBF mechanismVBF mechanism (v’)2

v’ should be small ++ WW++WW++

large SM bkglarge SM bkg

Wb fusionWb fusion (1)2

1 1 but

suppressed by b-quark PDF.

T bW, bW, ttZZ clear signalclear signal

qq annihilationqq annihilation (cot)2

Wide range in cot possible.ZH

ee++ee--

clear signal

Little Higgs SearchesJ. E. Garcia RTN – December 03

ZH Zh with h bb 9

hh

ZH

ZZ

l +

l -

bbbb

2 TeVhh

bb

bbZH

ZZ

l +

l -

1 TeV

Cuts

Background: Z + jets

Cuts

|| < 2.5 (jets and leptons)

PT(Z) > 250 GeVPT(h) > 250 GeVb-tagging

|| < 2.5 (jets and leptons)

PT(Z) > 500 GeV PT(h) > 500 GeV b-tagging

Little Higgs SearchesJ. E. Garcia RTN – December 03

Signal and background 10

b-tag: b = 40%, Ru = 100 Inside mass window:S = 15 SB = 8 B

= 5

b-tag: b = 50%, Ru = 100 Inside mass window:S = 195 SB = 16 B

= 50

M(ZH) (GeV)

MZ = 1 TeVH

M(ZH) (GeV)

MZ = 2 TeV

H

L = 3·105 pb-1

cot = 0.5L = 3·105 pb-1

cot = 0.5

Eve

nts

Eve

nts

Little Higgs SearchesJ. E. Garcia RTN – December 03

Discovery region ZDiscovery region ZH H Zh Zh 11

L = 3·105 pb-1

S/B > 5 N > 10

h(120) bb

ZH Zh l +l - bbWH Wh l bb

Little Higgs SearchesJ. E. Garcia RTN – December 03

J.E. Garcia RTN – December 03

PHD WorkPHD Work

SCT beam test analysis:Tracking efficiency, noise occupancy, collected charge, S/N but also several studies: tracking with standalone SCT, dependencies on incidence angle, studies with LHC-like bunch structuring…

Little Higgs Searches:Capability of the ATLAS detector to find particles predicted by the Little Higgs Models. In particular new gauge bosons in the channels: WH W H and ZH Z H

b-tagging studies:b-tagging performance of the ATLAS detector for high pT jets applied to the Little searches and for the benchmark channels W H(120) and W H(400). Using the signed impact parameter b-tagging algorithms.

mh = 200 GeV

BR(h W+W-) =

74 %BR(h ZZ) = 26

%

ZH Zh 13

q

q

cot cot 2

(cot cot 2) 2

(cot )

(cot = 0.5) mh = 120 GeV

BR(h bb) = 66

%BR(h ) = 0.2

%

ZH

hh

ZZ

Rat

io

0.5

Little Higgs SearchesJ. E. Garcia RTN – December 03

b-tagging 14

< pT (b)> = 220 GeV < pT (bb)> = 800 GeV

115

0.5

MZ = 1 TeVH

MZ = 2 TeVH

~ 100

0.4

Little Higgs SearchesJ. E. Garcia RTN – December 03