analysis of the tile-cal (atlas) prototypes and study of higgs production at lhc

ANALYSIS OF THE TILE-CAL (ATLAS) ANALYSIS OF THE TILE-CAL (ATLAS) PROTOTYPES AND STUDY OF HIGGS PROTOTYPES AND STUDY OF HIGGS

PRODUCTION AT LHCPRODUCTION AT LHC

SANTIAGO GONZÁLEZ DE LA HOZSANTIAGO GONZÁLEZ DE LA HOZ19 - DECEMBER - 200019 - DECEMBER - 2000

SUMMARYSUMMARYIntroduction

Theoretical motivations to the Minimal Supersymmetric Standard Model (MSSM).

The experimental setup (LHC and ATLAS).

Test beam performance of the TileCal prototypesThe 1997 test beam

Analysis of the data for the Extended Barrel Modules 0.The 1998 test beam

Analysis of the data for the Barrel Module 0.

Higgs decay to top quarks at hadron colliders. Search for MSSM Higgs in the top quark decay mode using a fast

simulation package for ATLAS (ATLFAST) Comparison between full and fast simulation of ATLAS detector Discovery potential of the ATLAS detector for the SM and MSSM

Higgs boson

ConclusionsSANTIAGO GONZÁLEZ DE LA HOZ 19-December-2000

INTRODUCTIONINTRODUCTION

SANTIAGO GONZÁLEZ DE LA HOZ 19-December-2000

THEORETICAL MOTIVATIONSTHEORETICAL MOTIVATIONSThe Standard Model (SM) is the most succesful yet

developed model to explain the physics of the fundamental particles and their interactions.

The SM gauge group is the product SU(3) x SU(2) x U(1), associated with the colour,weak and hypercharge symmetries.

The fermion content of the model is divided into two categories: QUARKS AND LEPTONS.

There are six types of quarks. Also, there are six types of leptons.

The gauge bosons are: the massless gluons of QCD, the massives W and Z of the weak interaction, and the massless photons of electromagnetism.


THEORETICAL MOTIVATIONSTHEORETICAL MOTIVATIONS

The most important question of the model is the origin of the masses.

The question can be answered by the Higgs mechanism, which requires the Spontaneous Symmetry Breaking.

The best experimental verification of the mechanism would be the discovery of the Higgs boson.



The SM answers the questions of the structure and stability of matter with six types of quarks, six leptons, and the four forces.

But the SM leaves many other questions unanswered:


•Why are there three types of quarks and leptons of each charge?•Is there some pattern to their masses?•Are there more types of particles and forces to be discovered at yet higher-energy accelerators?•Are the quarks and leptons really fundamental?•What particles form the dark matter in the universe?•How can the gravitational interactions be included in the SM?

THEORETICAL MOTIVATIONSTHEORETICAL MOTIVATIONSThe standard way beyond

the SM:


The same fundamental Fieldswith NEW interactions

Supersymmetry (SUSY)

Grand Unification


What is SUSY?The general idea The strategy

Unification of spin 2 & spin 1 forces within unique algebra is ONLY possible for SUSY


Unification of all forces of Nature

Increasing unification towards smaller distances including

Gravity

Photon, Gluon, W, ZS= 1

GravitonS = 2


The SUSY theories postulate that every particle we observe has a massive particle partner. For example, for every quark there may be a so-called "squark".

Spin 0 Spin 1/2 Spin 1 Spin 3/2 Spin 2


Q | Boson > = | fermion >

Q | Fermion > = | boson >

Q is the new generator of SUSY algebra:

The Higgs supersymmetry sector requires two Higgs doublets. After electroweak symmetry breaking, the physical states of the Higgs boson are two charged (H±) and three neutral (h, A, H).


The Minimal Supersymmetric Standard Model (MSSM)(The supersymmetric extension of the SM)

MSSM spectrum of particles


Chiral Supermultiplets

GaugeSupermultiplets

squarksquarks

(3 families)

Sleptonsleptons

(3 families)

HiggsHiggsinos

gluinogluon

WinosW bosons

binoB boson


For the SM particles and the Higgs bosons the R-parity is +1, while for all the squarks, sleptons, gauginos and higgsinos is -1.

If it is exactly conserved, this has three extremely important phenomenological consequences:


The lightest supersymmetric particles (LSP) must be absolutely stable.Each sparticle decays into a state which contains an odd number of LSPs.In collider experiments sparticles can be only produced in pairs.

PRB L S ( ) ( )1 3 2

R-parity: New symmetry which has the effect of eliminating the possibility of

baryon (B) and lepton (L) violating terms in the renormalizable potential.


This model contains supersymmetry breaking

In the MSSM the electroweak symmetry breaking requires two Higgs doublets and five (H±, A, H, h) physical states of the Higgs boson (just one in the SM).

The Higgs masses and coupling can be expressed in terms of only two parameters (mA, tan):

The pseudoscalar mass The ratio of the vacuum expectation values of the Higgs doublets


Slectron with the same mass as the electron has not been

discovered yet

THE EXPERIMENTAL SETUPTHE EXPERIMENTAL SETUPTo look for new physics

(Higgs boson), the next research instrument in Europe’s particle physics is the Large Hadron Collider (LHC).

The LHC is: a proton-proton collider working at high-energy

(14 TeV) with a high luminosity

(1034cm-2s-1).The LHC collider will be

built in the existing LEP tunnel.

The LEP/LHC injector system (Linac, PS and SPS)

19-December-2000SANTIAGO GONZÁLEZ DE LA HOZ

THE EXPERIMENTAL SETUPTHE EXPERIMENTAL SETUP

ATLAS (A Toroidal LHC Apparatus).

ATLAS collaboration involves 34 countries.

The design considerations for ATLAS detector are: good EM-calorimetry for e,

identification and measurement. Hermetic jet and Emiss calorimetry. Efficient tracking at high

luminosity for lepton measurements, b-quark tagging and e, identification.

and heavy flavour vertexing and reconstruction capability of some B decays.


THE EXPERIMETAL SETUPTHE EXPERIMETAL SETUPATLAS calorimetry:

The EM calorimeter system is contained in a cylinder of outer radius 2.25 m and a total length of 6.65 m.

The Hadronic calorimeter barrel system has an outer radius of 4.23 m and a total length of 12 m.

The Electromagnetic end-cap, Hadronic and Forward calorimeters are housed in the same cryostat

Crucial role at the LHC: Detectors are required to measure

the energy and direction of: photons and electrons isolated hadrons and jets, the missing transverse energy.


THE EXPERIMENTAL SETUPTHE EXPERIMENTAL SETUP

The Hadronic Calorimeter (TILECAL): It is based on a sampling technique with plastic scintillator plates (tiles)

embedded in an iron absorber matrix. The tiles are placed in the perpendicular plane to the beam axis and the read

out is performed by optical fibres and routing them to the photomultipliers. The calorimeter is segmented in three layers. The barrel and extended

barrels are divided into 64 modules.


TEST BEAM TEST BEAM PERFORMANCESPERFORMANCES


TEST BEAM PERFORMANCESTEST BEAM PERFORMANCES

Test beam results related to the hadron responses for prototypes and modules zero of the Barrel and Extended Barrel will be presented.


Features of the hadroniccalorimetry

Hadronic calorimeterperformaces

Rapidity || < 5

Granularity x = 0.1 x 0.1 || 3 x = 0.2 x 0.2 || > 3

Energy resolution 50%/E 3% for || 3100%/E 10% for 3<|| < 5

Energy linearity 2% up to a transverse energy of4TeV

Noise Less than 5 GeV(low energy jet)

Total thickness 10 interaction lengths ()

Jet identification 1% accuracy

Jet-jet mass reconstruction 1% error on the top mass

In order to reach the physics goals some hadronic calorimetry requirements are necessary.

TEST BEAM PERFORMANCESTEST BEAM PERFORMANCESThe non-compensation concept.

If a hadron interacts strongly develops a shower of particles that can be grouped as:

High-energy (+, -, o, p, n) Low-energy (, p, n ~1-10 MeV) don’t

contribute to a measurable (visible) energy In a hadronic shower we distinguish an

electromagnetic and purely hadronic component,

e/ ratio between the visible energy released by electrons and pions of equal incident energy.

e/ 1 non-compensation e/ > 1 in our case


To achieve compensation: designing an intrinsically compensated

calorimeter (U, Pb, etc..) in off-line analysis using different weights for the

electromagnetic and hadronic components of the shower.

ANALYSIS OF THE 1997 TEST BEAMANALYSIS OF THE 1997 TEST BEAM

Two Extended Barrel modules 0 were tested at CERN in October 1997, one from Barcelona (BCN) and the other from Argonne (ANL), together with the five 1 meter old modules.

The Calorimeter modules were installed on a table that can be rotated, accessing the towers of different values.

Test beam energies from 20 to 400 GeV along the different values of , from -0.8 up to -1.4 have been used in this analysis.



O n th e b eam ch am b ersto e lim in a te th e b eam h a lo

O n th e sc in tilla to r ch am b ersto e lim in a te th e even ts w ith

s im u ltan eou s p artic les

A p p lied w ith th e ag reem en to f th e co llab ora tion

C U TS




The evolution of the linearity and resolution in the data reconstruction have been studied in three steps:

Raw dataBenchmark methodH1 weighting method

E E E ERAW ANLcorr

BCNcorr

OLD

RAW DATA



Energy(GeV)

/(%)

/(%)

20 16.550.04 2.030.03 12.20.2 16.110.05 2.230.02 13.90.2

40 34.170.10 3.300.08 9.60.2 33.720.08 3.300.08 9.80.2

50 42.250.11 3.370.09 7.970.21 44.740.13 4.090.08 9.150.21

80 69.010.12 5.320.09 7.710.13 72.200.13 5.900.09 8.170.15

100 86.240.30 5.940.10 6.890.12 90.080.15 6.980.11 7.670.12

180 160.60.3 9.160.23 5.710.14 168.60.3 11.70.2 6.940.11

300 275.50.3 16.80.3 6.090.10 282.30.4 19.60.3 6.950.10

400 373.80.4 23.50.4 5.780.11 380.00.5 24.90.3 6.550.10

BCN module for BCN module for =-1.1=-1.1 BCN module for BCN module for =-1.2=-1.2


BENCHMARK METHODThis method tries to correct the effect of the lateral

and longitudinal leakage.

X = 1.26 GeV/pC (The conversion factor from pC to GeV for the Extended Barrel)

A-1= 0.17B = 0.31


E X E E A E E BETOT TOTANL

TOTBCN

SANL

SBCN

OLD ( )( )1 3 3

ANALYSIS OF THE 1997 TEST BEAMANALYSIS OF THE 1997 TEST BEAMH1 WEIGHTING METHOD

The energy in each cell is corrected by a parameter which depends on the energy of the cell:

The ai are obtained from the data at each energy:

where is the energy sum of all the cells within “i” energy interval.

Eold is the energy released in the old modules.The set of correction parameters ai is determined minimising

the expression:


E a Ecellcorr

i cell

E a E a E BEcorrk k

n nk

old 1 1 .......

E Eik

cellcells i

N E E E Ecorrk

beamk N

corrk

k Nbeam 2 2

1 1

( ) ( )

, ,


Parametrizing the ai : (13+1) x 8 beam energies = 112 param.


a pp

Eicell

12

The parameters p1, p2 and B (old modules) are expressed as a function of the beam energy.

We have expressed the entire set of corrections by two sets of simple functions, containing only a total of 7 parameters.


The aim is to reconstruct the pion energy assuming no knowledge of the beam energy:

Realistic energy reconstruction can be done using the raw data as the initial estimate of the particle energy; the procedure may be iterated until it converges.

RESULTSLinearity of the RAW DATA


MODULE RMS

BCN -1.1 4%

BCN -1.2 5%

ANL -1.1 4.2%

ANL -1.2 4%


Linearity plots obtained with the Benchmark method


Linearity minimizing the functional with the Lagrange multiplier (112 parameters)

MODULE RMS

BCN -1.1 4.5%

BCN -1.2 3.8%

ANL -1.1 4.8%

ANL -1.2 5%

MODULE RMS

BCN -1.1 0.4%

BCN -1.2 0.4%

ANL -1.1 0.34%

ANL -1.2 0.12%

ANALYSIS OF THE 1997 TEST BEAMANALYSIS OF THE 1997 TEST BEAMLinearity with the beam energy after the pararametrization (7 parameters)


Linearity plot comparing the method which does not use the beam energy with the one which does

MODULE RMS

BCN -1.1 1.2%

BCN -1.2 3%

ANL -1.1 1.8%

ANL -1.2 2.9%

MODULE RMS

BCN -1.1 2%

BCN -1.2 3.5%

ANL -1.1 2.2%

ANL -1.2 3.2%

a is the statistical fluctuations in the shower development b is the constant term dominant at high energies c is the noise term (0.06 GeV).

E

a

Eb

c

E

%%


Resolution plots applying all the described methods A fit of the data is performed in the way:




Method Module a% b%

RawData

BCNBCNANLANL

-1.1-1.2-1.1-1.2

46.70.943.71.251.70.849.91.4

5.340.084.800.085.090.086.040.08

BenchmarkBCNBCNANLANL

-1.1-1.2-1.1-1.2

50.11.452.21.551.51.559.11.9

3.100.104.210.124.870.123.710.16

H1 with112 param.

BCNBCNANLANL

-1.1-1.2-1.1-1.2

40.00.840.50.540.50.836.31.0

3.860.063.160.093.870.064.890.06

H1 with7 param.

BCNBCNANLANL

-1.1-1.2-1.1-1.2

45.10.745.20.645.40.748.61.0

2.660.072.550.142.990.063.760.25

H1not

using thebeam Energy

BCNBCNANLANL

-1.1-1.2-1.1-1.2

45.60.747.80.645.20.743.71.0

2.710.072.250.063.100.073.910.07

ANALYSIS OF THE 1997 TEST BEAMANALYSIS OF THE 1997 TEST BEAMREMARKS:

After applying a benchmark technique an improvement in the b parameter of the resolution was obtained but the linearity and the a parameter are still quite poor.

The linearity and the resolution of the Tile Calorimeter prototypes improve using H1 method.

The results are compatible for the two modules and for the two different values of .

The resolution degrades somewhat when no knowledge of the particle energy is assumed, being better than the obtained with the other methods.

The average resolution for the Extended Barrel is:


E E E

45 6%

2 9%006.

.

The statistical term is less than 50%less than 50%(inside of requirements)

The constant term is around 3%around 3%(inside of requirements)

The average RMS for the Extended Barrel modules is 2.2% (requirement 2% up to 4 TeV).


e/ responseThe response obtained for electrons and pions gives the

possibility to extract the e/h values.e/h is the ratio of the calorimeter responses to the

electromagnetic and non-electromagnetic (purely hadronic) components of hadron showers.

The e/h ratio was extracted from the data by fitting the expression:


e e h

e h E

/

( / ) . ln( )1 1 0 11

The value e/h = 1.38 corresponding to = -1.1 is in good agreement with the 1.36 obtained from previous

studies.


One Barrel Module 0 was tested at CERN in July 1998, together with the five 1 meter old modules. The same scanning table as for the test beam in 1997 was used.

Test beam energies from 20 to 400 GeV along different values of , from -0.25 to -0.55 have been analysed.

Cuts were applied in the beam chambers to eliminate the beam halo and events with simultaneous particle in the scintillator chambers (the same idea that in 1997 test beam).




The data obtained in the test beam has been compared with Monte Carlo simulation: GCALOR package (GEANT3.21 and DICE) many features of the module 0 are not yet implemented in the simulation

source code: Fluctuations on the response of the fibres and tiles, including tile-to-tile and

fibre-to fibre fluctuations; The electronic noise effect in the response of the module 0 to the particle

beams.

The evolution of the linearity and resolution in the data reconstruction have been studied in two steps:

Raw dataH1 weighting method

E E ERAW Mcorr

OLD 0

RAW DATA



Energy(GeV)

/(%)

/(%)

20 15.580.03 2.300.02 14.770.15 15.960.04 1.990.03 12.470.22

50 41.050.07 4.090.06 9.960.14 40.750.08 3.680.06 9.030.16

80 65.740.10 6.350.09 9.650.14 65.410.12 5.210.10 7.970.16

100 81.490.14 7.120.10 8.740.12 82.180.13 5.680.11 6.910.14

150 123.30.3 9.570.21 7.760.17 123.80.2 8.290.17 6.670.14

180 148.20.2 11.640.15 7.850.10 149.10.2 9.110.21 6.100.14

300 251.50.3 19.290.25 7.670.09 248.70.3 14.580.39 5.860.16

400 326.90.4 25.360.31 7.750.08 332.10.5 19.300.48 5.810.15

Resolution for pions at =-0.35 for test beam data and Monte Carlo simulation.

Test beam data Monte Carlo


H1 WEIGHTING METHODThe same idea that in 1997. The energy in each cell, Ecell, is

corrected multiplying its value by a parameter ai, which depends on the energy of the cell.

RESULTSLinearity of the Raw Data


RMS

Test beam data -0.35 2%

Monte Carlo -0.35 1.3%


Linearity plots obtained with the Lagrange multiplier (112 parameters)


Linearity after the parametrisation with the beam energy (7 parameters)

RMS

Test beam data -0.35 0.46%


RMS



RMS



ANALYSIS OF THE 1998 TEST BEAMANALYSIS OF THE 1998 TEST BEAMLinearity plot comparing the method which does not use the

beam energy with the one which does


Resolution plots applying all the described methods



Method Module a% b%

RawData

M0M0M0M0

-0.25-0.35-0.45-0.55

59.11.956.31.556.51.545.21.4

48.31.556.31.456.61.255.21.9

5.600.086.880.105.350.085.100.11

6.010.086.900.115.750.065.200.09

H1M0M0M0M0

-0.25-0.35-0.45-0.55

41.11.340.71.245.91.043.21.0

42.81.045.71.042.61.141.01.2

5.440.085.330.084.220.084.870.10

5.220.083.700.105.000.115.100.10

E

a

Eb

E

%%

.0 06

Test beamMonte Carlo

ANALYSIS OF THE 1998 TEST BEAMANALYSIS OF THE 1998 TEST BEAMREMARKS:

The linearity and the resolution of the Tile Calorimeter prototypes improve using H1 method. The linearity for the Monte Carlo simulation is better than for test beam data but at high energies the hadronic shower simulation is insufficient.

The statistical and constant term in the resolution are very similar for the Monte Carlo simulation and the test beam data.

The results are compatible for the different values of . The resolution degrades somewhat when no knowledge of the particle

energies is assumed, being better than the obtained with the raw data. The average resolution for the Barrel is:


E E E

42 7%

4 8%006.

.

The statistical term is less than 50%less than 50%(inside of requirements)

The constant term is around 5%around 5%(requirement less than 3%)

The average RMS for the Extended Barrel modules is 1.5% (requirement 2% up to 4 TeV).


e/ response


e e h

e h E

/

( / ) . ln( )1 1 0 11

The e/h is greater for =-0.35 than for other ´s because the shower is better contained for =-0.55 (e/h =1.41) than

for =-0.35

MODULE a% b%

BCN -1.1 45.60.7 2.710.07

BCN -1.2 47.80.6 2.250.06

ANL -1.1 45.20.7 3.100.07

ANL -1.2 43.71.0 3.910.07M0 -0.25 41.11.3 5.680.08M0 -0.35 40.71.2 5.330.08M0 -0.45 45.91.0 4.220.08M0 -0.55 43.21.0 4.870.10

ANALYSIS OF THE 1998 TEST BEAMANALYSIS OF THE 1998 TEST BEAMComparison between Extended Barrel and Barrel module 0


MODULE RMS

BCN -1.1 1.2%

BCN -1.2 3.0%

ANL -1.1 1.8%

ANL -1.2 2.9%

M0 -0.25 1.4%

M0 -0.35 1.8%

M0 -0.45 0.8%

M0 -0.55 2.0%

The RMSRMS for the Barrel is better than for the Extended Barrels due to

the quality of the datafrom 1997

Statistical term Statistical term is similar

The constant termconstant term is less inthe Ext. Barrels. The Barrel

has more leakages than the E.B.

E.B.

B.

E.B.

B.

ANALYSIS OF THE 1998 TEST BEAMANALYSIS OF THE 1998 TEST BEAMThe e/h ratio is very similar for both calorimeter prototypes

(1.4) and there is a good agreement with previous precise studies and Monte Carlo.


MODULE (e/h)

BCN -1.1 1.380.01

BCN -1.2 1.480.01

ANL -1.1 1.520.02

ANL -1.2 1.600.02M0 -0.35 1.610.02M0 -0.45 1.390.01M0 -0.55 1.410.01

The H1 method seems to be flexible and powerful enough to represent a starting point for the effective jets reconstruction algorithm in the ATLAS experiment.

HIGGS DECAY TO HIGGS DECAY TO TOP QUARKSTOP QUARKS


SEARCH FOR MSSM HIGGS SEARCH FOR MSSM HIGGS The Higgs particle is

produced at hadron colliders through gluon-gluon, via virtual top quark loop. There is a large irreducible

background from the QCD production of top quarks.


The branching ratio is too small (10%) to be observable in SM case. In the MSSM case, the branching ratios are close to 100% for mH,mA > 2mt and for tan1.

H ttH A tt/

H A tt/ The decays cannot be distinguished experimentally one from each other, since the H- and A-boson are almost degenerate in mass.

SEARCH FOR MSSM HIGGS SEARCH FOR MSSM HIGGS The strategy used to identify tt events from H/A decays consists in

searching for WWbb final states. One top decay (tWb) has to be followed by the semileptonic decay of the W (Wl). The second W-boson is required to decay hadronically (Wjj).

The background processes can be classified into two categories: The irreducible background, consisting of


tt bl bjj The reducible background from W+jets containing multi-jet events.

The study has been performed using the data sample of the Monte Carlo simulation for ATLAS detector at LHC collider: ATLFAST, a fast simulation of the ATLAS detector. SLUG-DICE-ATRECON, for a sophisticated full detector simulation. PYTHIA 5.7 has been used to generate the signal and backgrounds in both cases.

The invariant mass of the tt pair have been studied for signal events with mH/A=370, 400 and 450 GeV for an integrated luminosity of 3104 pb-1 and 105 pb-1 and for tan1.5

SEARCH FOR MSSM HIGGS SEARCH FOR MSSM HIGGS The initial selection requires at last 4 reconstructed jets with pT>40

GeV and ||<2.5, two of them being labelled as b-jets and at least one reconstructed isolated lepton with pT>20 (20) GeV for muons and pT>20 (30) GeV for electrons and ||<2.5 at low (high) luminosity.

After the selection cuts are applied, the background from tt continuum dominates. After requiring top-pair reconstruction the background from non-tt sources (QCD jets, W+jets, etc.) can be neglected.

There is an interference between the signal and the background amplitudes which causes a suppression of the observability of the signal. This suppression has been estimated to be 30% for mH=370 GeV, 50% for mH=400 GeV and 70% for mH=450 GeV.

Two algorithms for reconstructing the invariant mass of the tt pair have been studied: All possible combinations of b-jets with reconstructed decay Wl and W

jj contribute to the mtt mass distribution. Only the combination with the best 2 is taken into account.


2 2 2 ( ) ( )m m m mbl t jjb t

SEARCH FOR MSSM HIGGS SEARCH FOR MSSM HIGGS


First algorithm All possible combinations

of b-jets with jj

Second algorithmjjb combination2=(mjjb-mt)2

The level of combinatorialbackground

Single top-quarkreconstruction in the

hadronic channel




of b-jets with l

Second algorithmlb combination2=(mlb-mt)2

jl background

The reconstruction ofWl is limited. The longitudinal

component of the can be extracted

solving the W massequation

Single top-quarkreconstruction in thesemileptonic channel




of b-jets with l and jj

Second algorithmonly combination

2=(mjjb-mt)2+(mlb-mt)2

The second algorithm improves substantially respect the first one:

1) the signal resolutionthe signal resolution2) the signal-to-the signal-to- background ratiobackground ratio3) the statistical the statistical significancesignificance

Reconstructionof top-quark pairs

First Algor. Second Algor.

Nom.Val.

mH

(GeV)

(GeV)mH

(GeV)

(GeV)370 390 36 372.8 13.9

400 415 39 401.7 16.4

450 440 59 446.8 21.6

First Algori. Second Algori

Nom.Val.

Signal Bgd. Sig.S/B

Signal Bgd. Sig.S/B

370 4400 68700 16.8 4500 34200 24.3

400 4050 85700 13.8 4200 39500 21.1

450 3250 107200 9.9 3200 52900 14.2

The first algorithm reproduces in more unbiasedway the shape and magnitude of the combinatorial

background to the hadronic and semileptonicchannels.

SEARCH FOR MSSM HIGGS SEARCH FOR MSSM HIGGS After to reconstruct the invariant mass a study in order to subtract

the signal peak from the background has been performed. The statistical error, the systematic error from overall normalisation and from the shape of the background have been taken into account.

The signal+background for mH/A = 370 GeV and 450 GeV using a polynomial to fit the background and a gaussian distribution on top of it.


1) The extraction of the signal would only be possible for Higgs masses above theextraction of the signal would only be possible for Higgs masses above the

kinematics peakkinematics peak of the background distribution which is around 400 GeV.2) For masses close to 400 GeV only an excess of events400 GeV only an excess of events above the continuum

background would be observed.

The discovery curves cover at best limited region in parameterspace, namely thatcorresponding to

2m2mtt<m<mAA<470 GeV<470 GeVfor tanfor tan 11

COMPARISON FULL AND FAST COMPARISON FULL AND FAST In order to be able to cross-check the results obtained with

ATLFAST, a total of 20000 events were simulated with the full simulation of the ATLAS detector (mA = 400 GeV and tan1).

The acceptances and the quantities involved in kinematics cuts have been compared.


Acc. electrons muons leptons jets bjets

Fast 0.90 0.77 0.88 0.41 0.62

Full 0.89 0.74 0.85 0.49 0.59

||<2.5pT>20

||<2.5pT>40

||<2.5pT>40

Due to the implementation of the jet energy threshold in both

simulations

COMPARISON FULL AND FASTCOMPARISON FULL AND FAST


Quantities involved

inkinematics

cuts

||

—

pT

—pT

pT

The ppTT mean value is greater in the full than in mean value is greater in the full than inthe fast simulationthe fast simulation because:

1) In full the pT is slightly overestimated dueto the calibration problems.

2)The electronic noise is taken into account

COMPARISON FULL AND FASTCOMPARISON FULL AND FAST


Top and Higgsmass

resolution

jjb

tt

lb

Fastsimulation

Fullsimulation

(GeV) (GeV)

t bjj 13.93 21.11

t bl 11.92 12.67

mtt 17.25 17.51) The two simulations packages are in good agreementgood agreement for the

kinematics acceptances and the quantities involved in the analysis.2) The top and Higgs mass resolutions are in reasonable agreementmass resolutions are in reasonable agreement,with the full simulation predicting resolutions which are 10-20%

worse than those from the fast simulation.3)The two simulations can be used in a complementary waytwo simulations can be used in a complementary way to

study physics channels:3.1) Full simulation can be used to check in detail the detector

performances.3.2) Fast simulation can be used for the production of large statistics

samples of events for the physics analysis.

DISCOVERY POTENTIAL DISCOVERY POTENTIAL


1)MH<2MZ:HH ZZ* ZZ* 4l 4lH H H H WW* WW* l lll2)MH>2MZ:dominant discovery channel is the four-lepton channeldominant discovery channel is the four-lepton channel3)(600-1000) GeV:H H WW WW l ljjjjH H ZZ ZZ lljj lljjH H ZZ ZZ ll ll

1)Large tan (as SM):

HH H H bb bb

H H ZZ ZZ 4l 4lH/A H/A H/A H/A 2) Low tan:

H/A H/A ttttA A Zb ZbH H hh hhHH tb tb

CONCLUSIONCONCLUSIONThe results obtained in the test beam of the Tile - Cal prototypes

are the following: The linearity and resolution of the Tile Calorimeter prototypes improve

using the H1 method. Also these results are compatible for the two prototypes used in the 1997 and 1998 test beam at different values of . In the ATLAS environment, the aim will be to develop an effective jet reconstruction algorithm. This method described here may be flexible and powerful enough to suit this purpose.

The linearity obtained with Monte Carlo simulation is better than for the test beam data but at high energies the hadronic shower simulation is insufficient and the shower descriptions became quite far away from reality.

The statistical and constant terms in the resolution are very similar for Monte Carlo simulation and test beam data.

The e/h ratio of a sampling calorimeter with an iron-scintillator structure is expected to be >1 as has been shown in this analysis and the value is in good agreement with the results obtained from previous precise studies.

A comparison between the barrel and extended barrel prototypes has been made. The resolution, linearity and e/h ratio for both prototypes are inside of the Hadronic Calorimeter requirements.


CONCLUSIONCONCLUSIONThe results obtained in the search for a Higgs boson via its decay to

top quarks in the MSSM are the following: The expected mass resolution mtt increases from 14 to 20 GeV as mH

increases from 370 to 450 GeV. This implies that a typical window to observe most of the signal would be between 28 and 80 GeV.

The signal-to-background ratio varies between 9% and 1% over the mass range from 370 to 450 GeV. For an integrated luminosity of 30 fb -1 (3 years at low luminosity) and tan=1.5 about 2120 signal events and 40000 background events are expected inside a mass window of 2m around mA= 400 GeV.

The extraction of the signal would only be possible for Higgs masses above the kinematics peak of the background distribution which is around mtt = 400 GeV.

For masses close to 400 GeV only an excess of events above the continuum background would be observed.

A limited region in parameter space has been found. This limit corresponds to 2mt< mA <470 GeV for tan1.

The results obtained for the mass resolution with mA=400 GeV using ATLFAST have been compared with a full detector simulation. The two simulation packages are in good agreement for the kinematics cuts acceptance, the quantities involved in the analysis and the top and Higgs mass resolutions.



Linearity plots obtained with the Benchmark method


Linearity minimizing the functional with the Lagrange multiplier (112 parameters)

MODULE RMS

BCN -1.1 4.5%

BCN -1.2 3.8%

ANL -1.1 4.8%

ANL -1.2 5%

MODULE RMS

BCN -1.1 0.4%

BCN -1.2 0.4%

ANL -1.1 0.34%

ANL -1.2 0.12%

ANALYSIS OF THE 1997 TEST BEAMANALYSIS OF THE 1997 TEST BEAMLinearity with the beam energy after the pararametrization (7 parameters)


Linearity plot comparing the method which does not use the beam energy with the one which does

MODULE RMS

BCN -1.1 1.2%

BCN -1.2 3%

ANL -1.1 1.8%

ANL -1.2 2.9%

MODULE RMS

BCN -1.1 2%

BCN -1.2 3.5%

ANL -1.1 2.2%

ANL -1.2 3.2%


Linearity plots obtained with the Lagrange multiplier (112 parameters)


Linearity after the parametrisation with the beam energy (7 parameters)

RMS



RMS



ANALYSIS OF THE 1998 TEST BEAMANALYSIS OF THE 1998 TEST BEAMLinearity plot comparing the method which does not use the

beam energy with the one which does


Resolution plots applying all the described methods

RMS



TEST BEAM PERFORMANCESTEST BEAM PERFORMANCES

A calorimeter consists of a matter block which serves to intercept primary particles and where all the energy is deposited in its interior.

General characteristics


The different response to electrons, muons and hadrons can be exploited for particle

identification

The average number of secondary particlesis proportional to the energy of the incident

particles

They are sensitive to charged and neutral

particles

Electromagenetic Calorimeter: and e- interact electromagnetically with the absorber materialHadronic Calorimeter: The hadrons interact strongly with the absorber material


BENCHMARK METHODThis method tries to correct the effect of the lateral

and longitudinal leakage.

X = 1.26 GeV/pC (The conversion factor from pC to GeV for the Extended Barrel)

A-1= 0.17B = 0.31


E X E E A E E BETOT TOTANL

TOTBCN

SANL

SBCN

OLD ( )( )1 3 3

analysis of the tile-cal (atlas) prototypes and study of higgs production at lhc

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