Higgs self coupling at e + e - Linear Collider

Higgs & EWSB session LCWS06 8-13 march Higgs self coupling P. Gay 1

Higgs self coupling Higgs self coupling at eat e++ee-- Linear Collider Linear Collider

P. Gay & Ph. Gris LPC Univ. B. Pascal -IN2P3


IntroductionIntroduction Standard Model

Higgs doublet ()

Higgs potential behaves as 22

212 )()( V

GeV24622 4hm

22

23

26 / hhhh m

the direct measurement of hhh

and

indirect measurement from mh sign of NP

Goal

Reconstruction of the Higgs potential

Experimental establishment of the Higgs mechanism

Benchmark for detector optimisation

Deviation between


Standard ModelStandard Model


DetectorDetector simulation simulation EE

E1

jetjetjet EEE /%40/


Processes @ 800 GeVProcesses @ 800 GeV

CIRCE/ TESLA

Expected signal for 500fb-1 is ~92 events

Generated w/ WHIZARD Impact of the beamstrahlung

No beamstrahlung

Beamstrahlung and

complete

Mh=120 GeV/c2

visE

104000.2873keeZZ

0.057110khhZ tri

0.05369khh tri

71903.47725kZZ

13890668.89.2MWW

6744222.41.5MZZ

254000.78720ktt

117610.0912keZW

342800.72925kZZZ

175556.96100kWWZ

482712.4360kWW

706422.65160khZ

3840260.41Mtt

55214.52825kttZ

80062.49820ktth

542270.184410kSignal

NGenProcess

104000.2873keeZZ

0.057110khhZ tri

0.05369khh tri

71903.47725kZZ

13890668.89.2MWW

6744222.41.5MZZ

254000.78720ktt

117610.0912keZW

342800.72925kZZZ

175556.96100kWWZ

482712.4360kWW

706422.65160khZ

3840260.41Mtt

55214.52825kttZ

80062.49820ktth

542270.184410kSignal

NGenProcess


Selections Selections

Selection in two branches

Evis < 500 GeV Evis > 500 GeV

4 jets 6 jets

Preselection signal background


“ “hhZ”-SelectionhhZ”-Selection

2

56

Z56

2

34

h34

2

12

h122hhZ σ

mmσ

mmσ

mmD

2hhZD

2hhZD

Background

signal

ghhh

contribution


B-tagging B-tagging For each event a b-tagging per jet is performed

Based on impact parameter information per track, combined per jet, to form a probability Calibration is performed with the integral of the negative part of the distribution and yields the probability that the track is coming from a light quark

Impact parameters and jet multiplicity are combined in a multivariable estimator

NB: better estimator may be achieved with 3D view

Not sensible to the boost (only transverse information used)

Calibration has been done at 500GEV

No beamstrahlung

Beamstrahlung and

complete


““hhZ”-SelectionhhZ”-Selection

4

1

)1(i

jetbtag iNNT

signal Background

btagT btagT

ghhh

contribution

]1,1[ ijet

NN

No

b-l

ike

jet

4 b

-lik

e je

t



eventNNeventNN

signal Background

ghhh

contribution



signal

Background+signal

)/( 264 cGeVM jb

ghhh

contribution


““hh”-Selectionhh”-Selection

2

34

h34

2

12

h122hh σ

mmσ

mmD

2hhD

2hhD

First stage of the selection

Final stage of the selection


““hh”-Selectionhh”-Selection

angle measured in the cme of the pair between the higgs direction and the boost axis

*cos

*cos

signal

Background+signal

ghhh

contribution


Numbers Numbers hhZ-selection vvhh-sel. Total

Process loose Tight

tth 17.36 2.62 -

ttZ 10.14 1.81 -

tt 98.0 - -

hZ 16.1 - 1.41

eeZZ 0.43 - -

ZZ 0.07 - 0.49

ZZ 8.15 - 0.37

tt 0.04 - -

ZZZ 2.74 1.03 -

WWZ 0.28 - -

Backg 153. 5.46 2.27 7.73

signal 34.4 22.0 8.49 30.5

Eff. (%) 42.6% 30.2% 37.3% 33%

2.5 4.2 2.6 4.93sbs

for 500 fb-1

GeV800s


InterpretationInterpretation

Counting event only

hhZ channel (6jets) %22/ hh channel (4jets) %18/

for 2 ab-1

Process hhZ sel. vvhh-sel.

Backg 21.8 9.1

signal 88.0 34.

Eff. (%) 30.2% 37.3%

8.2 5.2sbs

‘hh’

‘hhZ’

Combination and likelihood

%14/ ghhh/g0


hhZ @ 500 GeV hhZ @ 500 GeV Main steps (similar to 800 GeV)

3 selections


hhZ @ 500 GeVhhZ @ 500 GeV

HHZ Cme=500Gev

Mh=120 Gev/C2 Full polarised beams

for 2 ab-1

Process hhZ sel.

Backg 105.6

signal 124

Eff. (%) 36%

8.1sbs

%18/

NN>0.5

likelihood

NN>0.5


Higgs self coupling: a benchmark Higgs self coupling: a benchmark for detectorfor detector

Any improvements done on the the detector will save data taking

Impact of the Pflow resolution (fast simulation)

40%->30% move from 4.5 to 2 years data taking

LEP

E%30

E%40

E%60

BSS

LEP

E%30

E%40

E%60

BSS


Events clustered in 4 jets

Beamstrahlung included

GeVs 800@

1keeZZ

1kWW

1kWWZ

1khZ

1ktt

1kttZ

1ktth

1keeZZ

1kWW

1kWWZ

1khZ

1ktt

1kttZ

1ktth

Background “full simulation”~0.3 fb-1 simulated

Full simulationFull simulationLDC concept framework

MOKKA w/ HCAL sensitive material scintillatorParticle Flow Algorithm : Wolf in MARLIN RECO


hhZ @ 500 GeV

Event Display LDCEvent Display LDC


Full simulationFull simulation

Background

M34 (masse du Higgs)

20 Nbins entre 80 et 150 pour le background

PLOT

Background Background

Signal

12m 34m

GeVs 800@


Full simulation and ReconstructionFull simulation and Reconstruction

Reconstruction of is of importancePhotons are ~20% of jet energy

Motsly coming from

Challenge for calorimeters

Low energy photons

Example of improvement with

constraint on ° massGeVs 800@


Plo

ts g

iven

for

10

fb-1

“fast simulation” “full simulation”

“full simulation”

25 ab-1 simulated

Full vs Fast simulationFull vs Fast simulation

Background

Signal

GeVs 800@


SummarySummary@ 500 GeV, selection of the events 6 jets have been performed to hhZ final state.

@ 800 GeV, selections of the events with 4 and 6 jets have been performed to respectively cover hh and hhZ final states

Beamstralhung & ISR has been taken in account Realistic Fast simulation of the detector has been used

At center of mass energy of 500 GeV, hhZ process leads to

combination of hhZ and vvhh channel, at center of mass energy of 800 GeV, leads to %14/

%18/

With 2 ab-1

Full simulation is on the way

Higgs self coupling at e + e - Linear Collider

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