marcel vreeswijk (nikhef) introduction assembly station sag adjustment gluing bol-0 temperature...

Marcel Vreeswijk (NIKHEF)

• Introduction• Assembly Station• Sag adjustment• Gluing BOL-0• Temperature studies• Summary

The Making of the BOL-0BOL-0 @NIKHEFThe Making of the

BOL-0BOL-0 @NIKHEFNIKHEF ATLAS MUON group: H. vdGraaf, F.Linde, G. Massaro, M. Vreeswijk, P. Werneke


ATLAS-Muon

West side has expansion length o 0.1m in Xras

•

s

Muon system with air core toroid aims at 50um spatial (sagitta) precision in bending plane.Achieved by:• excellent alignment ~20um• precise drift tube chambers ~20um (RMS)


ATLAS-Muon


• Alignment based on RASNIK

s

Chambers consist of spacer + 2x3 drift tube layersIn-Plane system monitors internal chamber deformationsProjective alignment monitors chamber to chamber movements

•Alignment scheme:

Projective alignment

In-Plane

NIKHEF will produce the Barrel Outer Large chambers, 2mx5m, BOL (~100)This talk: BOL-0

Relative measurement of three points


Assembly Station


• Granite table: 6m x 2.5m

•Three bare Cross-Plates are positioned on the station, carried by sphere holders•The combs which will support the tubes are also visible•In the background: wiring station, Quality Control

setup(s)

Situation mid 99

North X

East Z

Up Y

s


Precision Mechanics


• intrinsic accuracy better than 10um

The quantities which affect the wire positions are checked and found to be precise within 10umGranite table has sag of 25um + 10um light on/off

s

Positioning combs and sphere holders Tools:

• Laser + optics (straightness combs),• silicon sensor (to line up combs),• Slof (height-meter), • tilt-meters (check Torque),• Balmonitor (dZ between multilayers)


Spacer


• Spacer monitored by RASASSituation mid 2000

Sphere tower with changeable block to adapt to tube layers

NIKHEF Comb

Frascati comb

RASAStower

‘Ear’ with sphere and RASAS-MASK

In-plane mask

In-plane lens

Xplate

longbeam

s

No Flexo


Sag Compensation• Sag compensation has been used manually.

• Three pressures: 2 x outer (practically equal) and inner Xplates.

Model Pressure (bar)longbeams crane sagbar XP total Predict from weight Observed

Outer + 32 17 10 10 69 3.5 3.0 - 3.4Outer - 0 17 10 10 37 1.9 1.2 - 1.4Inner + 0 0 20 10 30 0.8 0.4 - 0.5Inner - 64 0 20 10 94 2.4 2.2 - 2.3

weigth (kg)

After consistent results we adjusted the sag to obtain (almost) symmetric weight distribution

Sagcompen-sation tower

Additionalweight forsafety

s


Sag Compensation• Xplate sag before adjustment

s

Asymmetric sag Xplates, due to asymmetric weight distribution during gluing spacer -> Adjust

Chamber up

Chamber (upside) down


Sag Adjustment• Xplate sag after adjustment

s

After sag adjustment we observe (almost) symmetric sags for chamber up and down positions

Chamber up

Chamber (upside) down


Sag Adjustment+Compensation

•

s

Chamber before adjustement and compensation

Chamber after compensation


Assembly Station +Spacer

Summary:• Assembly Station alignment good for

wire position to the 10um level.

• Asymmetric distribution long-beams adjusted successfully.

• Sag (compensation) of cross plates understood within 20um.

• Observed sag of granite table of about 30um

s


Tube wiring + QC• Wiring Machine (NIKHEF)

Quality Control on drift tubes, specs:•Wire position: |Z,Y|<25um •Wire tension: 350gr+-5% (+batch 275gr)•Leak rate: He 2.5 x 10-8 lb/s (official: Ar 1.0 x 10-8 ) •HV check: <20nA @3000V

By mistake


QC-Wire position

Wire position: |Y,Z|<25um

Rejection 2%

s

1 tube was found with R>100um. A destructive check revealed: no twister in endplug

Coil

Drift Tube

EndPlug


QC-Wire tension

Quality Control on drift tubes, specs:•Wire tension: 350gr+-5% (+batch 275gr)

Rejection 5% (3%). >1 month after production, creep of the order of 1gr over >1 month

s


QC-Leak Rate

Quality Control on drift tubes, specs:•Leak rate: He (4 bar) 2.5 x 10-8 bl/s (official: Ar(3 bar) 1.0 x 10-8 )

Rejection 4%

10-1

s


• Quality Control on drift tubes, specs

QC HV Check

•HV 3000V , current <2.0nA

Rejection 4%

s

Current versus HV

0

20

40

60

80

100

2000 2500 3000 3500

HV (V)

Tube

cur

rent

(nA)

Current versus HV

Current versus time

0

10

20

30

40

50

9:00 11:24 13:48 16:12 18:36

Time (h)

Tube

curre

nt (n

A)

Current versus time

Accumulated excess current Tubes

0

5

10

15

20

25

0 200 400 600

Total # tested tubes

To

tal

# o

verc

urr

en

t tu

bes

AccumulatedOvercurrent Tubes

Overcurrent tubes


Gluing BOL-0

In the BOL-0 all tubes passed the QC. Different wire tensions are used. • Wire tension for layer 1-4: 350 gr (nominal) •For layer 5: 275 gr•layer 6: 275gr + 5 tubes with 350gr (interesting check X-ray tomograph)

s


Gluing BOL-0Problems:•Nozzle mounting very critical•Central glue ropes between tubes not uniform/symmetric

•Double amount of glue 103 (instead of 106, 2011) for central ropes which is more fluid•(keep nominal amount of glue for side ropes, 106)

Solutions:•Reduce Glue machine X speed by two (now ~10m/s)

Bigger central glue cilinder

Glue stop for tape

tube

glue

s

tube


Gluing BOL-0

• Stability Xplates during gluing

Start glue

Start glue

Layer 2

Layer 3

Yrasnik=2 x Sag

Start glue

Layer 1

Layer 1: dSag=7um

Layer 2: dSag=10um

•The sag of the xplates in layer 1 and 2 change in time. Glue crimp? Temperature?•Layer 3,4,5,6: Sag stable

s


Gluing BOL-0• RASAS monitors

SE

NW

SW

NE

Global Z,RASAS X

Global X

Global Y (up)

•Stability in Y appears very good ( for some layers the RASAS indicated problems which could be online corrected)

Global Z

•Relatively large Z movement layer 6 (spacer floats on glue?)

s

Lever arm in stacking block


BOL-0

•Tubes press glue away?•Tubes deform?

•Affects precision praxial platforms!

Thickness Multi-layers BOL0 has tape (50um) between tubes at one side

2 layers

3 layers

Much work..

s

Tape seems to improve tube distance


BOL-0Heat Studies (No flexoos in BOL-0)

s

Yrasnik= 2 x sag

XplateInplane

Yrasnik= 2 x sag

The BOL-0 was covered with heat blankets, producing 50W/m2

Gradient between MLs: 2.5 to 4 oC

Sag of Chamber: 200um 50 to 80 um/oC= acceptableSag of xplate: 25um 6 tp 10 um/oC = acceptable


Summary• We have constructed BOL-0 at NIKHEF

s

NEXT•Chamber will be scanned at CERN in Xray tomograph•Automise QC setups. Most notably: leak rate + HV (tubbies)•If OK, Production starts April 1th, 2001•Produce chamber/2weeks


Production• Production of 100 BOL chambers will start April

1th

• How many people are involved?

•People who do the work

•People who do the ‘visual inspections’

•And ‘stuurlui’


Assembly Station


• Accuracy combs and sphere holders

• The intrinsic accuracy of mechanics is good• The granite table has a relatively large sag of about 25um. Additional effects of 10um with light on and off

(temperature gradient)

Positioning combs and sphere holders Tools:

• Laser + optics (straightness combs),• silicon sensor (to line up combs),• Slof (height-meter), • tilt-meters (check Torque),• Balmonitor (dZ between multilayers)


Assembly Station


• The Balmonitor is a Cross-Plate equipped with lenses. Each lens is combined with a ‘fork’ on the combs to form a RASNIK system

•The Balmonitor measures the Z and Y difference between Sphere tower and Comb between North and South. (Z difference between Multilayers)

•Additionally the Balmonitor is used to check for height difference between sphere towers at the reference and non-reference side (West/East)

s


Assembly Station



Gluing BOL-0

Layer 1

Layer 2


RASAS• RASAS- stacking

The stacking has been checked using the RASAS monitors. The bare spacer has been put into A+, A-, C+ and C- orientations for the 3 stacking blocks

The nominal steps are dY=26.011 um and dZ=15.017 um

After a fit of the Mask-orientations (4), the residuals are shown below.


Assembly Station• RASAS- block deviations

The fitted block deviations are within 10um as expected from measurements with a 3D coordinate machine.

The expectation values of the masks are extracted from:

• CCD angles from dedicated calibration, 0.1 mrad

•RASNIK measurements of relative angle from the MASK and CCD (0.1 mrad).

In mrad

um


Assembly Station• RASAS -temperature stability

The Xplates are made off aluminum and expand about 24um/C/m.

East side has expansion length of 2.4m in Xras


XPlate RASNIKs


• The calibration (zero level) of the Xplate rasniks can be extracted from:

1) The RASNIK reading for the up and down position of the bare Xplates before gluing the spacer. Problem: old data, components touched.

2) The response for the up and down position (A+,A-) of the spacer. Problem: large effects due to large gravitational force, leading to possibly large second order effects

3) The RASNIK response for the up and down position of the airborne spacer. Problem:hysteres due to bad design of crane beams.


XPlate RASNIKs


• calibration Xplate rasniks, by rotation of airborne (horizontal) spacer

This method yields consistent results compared to up/down positions of the bare Xplates


In-Plane RASNIKs


• The calibration of the In-Plane (Y) is extracted from data in A+, A-, C+, C- positions.

• A model to account for asymmetric weight distribution over the XPs in the + and -- orientations has been used to fit the data.

0 1 2 3W E

A+ Y -28 -45 -50 -26A- Y 102 195 200 94

E WC+ Y -18 -55 -50 -41C- Y 82 205 200 114

0 1 2 3W E

A+ Y -41 -42 -48 -25A- Y 111 192 198 95

E WC+ Y -25 -48 -42 -41C- Y 95 198 192 111

Data of the four in-plane systems:

Although steps appear large and uncontrolled, the data is reasonably well described by the model (10 um)

Model

Data


In-Plane RASNIKs


• Model Parameters

Implications:

1) Sag of Xplates as function of additional weigth consistent with data.

Model Datasag@LO sag@LO

outer XP + 57 53outer XP - 37 35inner XP + 36 40inner XP - 76 83

FEA predicts slope of 0.56!!!!!

2) Sphere block in centre are off in height by appr. 30um as confirmed by laser+Si-sensor and alsoqualitatively by optical alignment tool!!!!!

3) In A+ position, when the spacer was glued, longbeam weight on outer Xplates!!!!

slope 1 XP sag um/kgWoff 36 XP Sag for 32 kgMW 32 Middle Sphere tower alignment (um)ME 25 Middle Sphere tower alignment (um)Was 16 Weigth difference on outer XP in +/-

Uncertainties 10%


Sag Compensation


Sag Compensation

0.4 bar


Sag Compensation• Shape without sag compensation


Sag Compensation• Shape with sag compensation


The road to BOL-0Date Item Comment1999 Cleanroom Prepare assembly stationApril 2000 Spacer Construct spacer

Nov. 2000 Setup ready Glue machine studies15/11 1st layer Gluing central ropes16/11 Platforms Problems with intrinsic

accuracy20/11 Spacer Spacer on 1st tube layer21/11 2nd layer Gluing central ropes22/11 Spacer Spacer+1st+2nd layer23/11 3rd layer First layer to layer;

problems with glumachine

24 –28/11 Glu machine Change CentralCilinders

29/11 4th layer Ok

1/12 5th layer Ok5/12 6th layer 20um Z shift


Gluing BOL-0• Layer 3


In-Plane RASNIKs


• The calibration of the In-Plane (Y) is extracted from data in A+, A-, C+, C- positions..


Gluing BOL-0• Result for side (106) and central (103) ropes

Central rope

Central rope

Central rope

Central rope

Central rope,sometimes bad(stability glue unit?)

tube


• The Standard Model• The Higgs particle; recent results!!!!• The D0 experiment• The proposal• Costs• Conclusions

Hunting the Higgsby online B-tagging


The Standard Model

Theoretical Mass constraints:•An upper limit is related to unitary and set by the Higgs self coupling.•The stability of the Higgs potential provides a lower limit. Otherwise: new physics has to become manifest at some scale !!!!

•The Standard Model=Relativistic Quantum Field theory with Local Gauge SymmetrySU(2) x U(1)•Higgs mechanism endows particles with mass, while maintaining Gauge Symmetry. •The Higgs mechanism gives rise to a particle called the Higgs Boson, which has been elusive so far.

Not allowedNot

all

owed

All

owed


The Higgs Particle

MHiggs<245 GeV

The mass of the Higgs can be predicted by the combination of precision measurements (from LEP) which are sensitive to higher order Quantum Corrections that involve a Higgs Boson.

The yellow band is excluded by the direct searches at LEP

HiggsZ

b

b

tZ

b

b


The Higgs ParticleThe LEP programme just has been extended by one month (until November 2th).

The LEP experiments have reported an excess of events above other standard model processes, compatible with a Higgs boson of about 114 GeV!

e

eZ

Z H

Direct searches at LEP

Z -> qqH -> bb

Signature:4 jets (2 with B-meson)

Invariant mass of B quark jets. (in red: theoretical contributions for Mhiggs=114GeV)

Deviation from other SM processes. (a handful events…)However, observed Xsection to high.


The Higgs Particle

Signal+Background hypothesis:Likelihood Ratio (signal/background)

Background

Signal Data

Direct searches at LEP(ALEPH)

•The Higgs might be around the corner.

•LEP will most certainly not be granted another year (the future of CERN is chosen to be LHC from 2005, which can do the job better …. but, TEVATRON in 2001 gets the first shot)

•Optimistically, if LEP claims a 3-4 std discovery, it will be shared with TEVATRON. The TEVATRON (and later LHC) will have the great task to study what was discovered.


The Higgs Particle

•The Higgs might be around the corner.

•LEP will most certainly not be granted another year (the future of CERN is chosen to be LHC from 2005, which can do the job better …. but, TEVATRON in 2001 gets the first shot)

•Optimistically, if LEP claims a 3-4 std discovery, it will be shared with TEVATRON. The TEVATRON (and later LHC) will have the great task to study what was discovered.

This talk: concentrate on the search for a low

mass Higgs (M<140 GeV) at D0 (TEVATRON)


• The Standard Model• The Higgs particle; recent results!!!!• The D0 experiment• The proposal• Costs• Conclusions

Hunting the Higgsby online B-tagging


Higgs Production

The strong process gg --> Higgs is the main production channel.

Electroweak (Associated) Higgs production of Z or W important, because of signature.

•Higgs production Cross Sections


Higgs Decay

•Up to a mass of 140 GeV the Higgs will predominantly decay into b quarks. •Other decay modes require high luminosity (LHC)

•Branching Ratio


Higgs: Recent ResultsThe LEP programme just has been extended by one month (until November 2th).

The LEP experiments have reported an excess of events above other standard model processes, compatible with a Higgs boson of about 114 GeV!

e

eZ

Z H

Direct searches at LEP

Signature:4 jets (2 with B-meson)

Invariant mass of two b quark jets. (in red: theoretical contributions for Mhiggs=114GeV)

Deviation from other SM processes. (a handful events…)However, observed Xsection too high.

b

b

q

q


What if we can trigger Higgs events by the decay into b-quarks?

Higgs Selection

1. Conservative: When a Higgs event is identified by a secondary vertex allows lower (missing) energy cuts more events survive for offline analysis. (also increases potential top-quark analysis)

2. But… if the algorithm is successfully it may even be possible to study the single Higgs channel. (only 1% efficiency gives already 10 Higgs/year)

3. Furthermore, studying online b quark tagging provides excellent starting point for the final offline analysis. (also for TOP quark analysis)

B meson travel several mm before they decay, leading to a secondary vertex.

The main enemy is the enormous QCD ( a standard process) background.

doprimaryvtx

secondaryvtx

Lxy


Higgs Online Selection

Associated production of Higgs and Z or W is relatively easy to trigger. For example: when the Z decay to neutrinos, the event can be recognized by large missing energy (but low event rate and efficiency).

doprimaryvtx

secondaryvtx

Lxy

Single Higgs production only accessible with powerful b trigger, using tracking information.


B meson

In the offline analysis all (low mass) Higgs studies need to require B tagged jets.

We propose to introduce the B tagging already in the online event selection.


•Present expectation

What if we can trigger Higgs events by the decay in to b-quarks?

1. Conservative: When a Higgs event is identified by a secondary vertex lower (missing) energy cuts more event survive for offline analysis. (also TOP)

2. But… if the algorithm is successfully it may even be possible to study the single Higgs channel. (only 1% efficiency gives already 10 Higgs/year)

3. Furthermore, studying online b quark tagging provides excellent starting point for the final offline analysis. (also for TOP quark analysis)

Higgs rates

LEP2 searches EW fits

1 year


Higgs rates

•Single Higgs production is usually not considered in performance studies (expected to be too difficult)

•Associated Production: Need to trigger and cut on (missing) transverse energy and offline B tagging, leading to only a few surviving events

Signal/Background Z,W leptonic hadronic (1 year Mhiggs<130GeV

WH + ZH 8/59 4/2800

gg H

WHZH

1.0 10000.3 3000.18 180

QCD 106 109

[pb] (mH=100 GeV)Events/year (1 fb-1)

LEP2 searches EW fits

1 year


Higgs rates

•Single Higgs production is usually not considered in performance studies (expected to be to difficult)

•Studies of associated Higgs production, with Z or W decaying leptonically (34%) or hadronically (66%), show only a few surviving Higgs events, after trigger and cuts.

•All channels use cut on (missing) transverse energy.

Signal/Background leptonic hadronic

Expected in 1 year Mhiggs < 130GeV

WH + ZH 8/59 4/2800

gg H

WHZH

1.0 10000.3 3000.18 180

QCD 106 109


What if we can trigger Higgs events by the decay in to b-quarks?


The proposed research programme

Summary

The selection of top and Higgs events by B tagging is of crucial importance

Proposal

•Develop an algorithm to select online the events with a displaced secondary vertex from a B meson

•Such an algorithm most likely uses an Artificial Neural Network technique.

•The algorithm can be implemented at the level 2 global processing stage. The present hardware allows to add the needed processor.

•The analysis work can be performed at NIKHEF (UVA) in close collaboration with the already existing (dutch) D0 group.

•If successful (online secondary vertex tagging has not been attempted before), this approach will be transferred to the ATLAS experiment.


Costs

EquipmentFast Computer for Analysis 10kHardware for the L2 system

25kTest stand at NIKHEF

15k10k

Total Equipment 60kTravel to Fermilab (per year 20k) 100kPersonnel

Total Costs (HFL) 160k +personnel

UD position 5 yearsAIO position 4 years

Processor+interface

VME crateTest Electronics

The trigger system of D0 is a multimillion dollar project and has been developed over the last years.

The Netherlands (NIKHEF) is paying yearly contributions to D0. Additionally, NIKHEF made some hardware contributions.

The project proposed here, aims at an extension of the already existing trigger system and therefore requires only a moderate hardware investment.


Conclusions•Driven by the exciting recent results from LEP, we concentrated on the low mass Higgs search using the D0 detector at the TEVATRON.

•The proposed research programme also aims at top quark studies.

•To achieve our goals, we propose to tag secondary secondary vertices to identify B mesons in the online event selection.

•The trigger system of D0 needs to be extended and a state of the art selection algorithm has to be developed.

•At a somewhat larger time-scale the approach will be transferred to the ATLAS experiment at the LHC.


FERMILAB (USA)High Energy Physics in the Wild West!

Fermilab is situated near Chicago (USA). The TEVATRON is four miles in circumference.


TEVATRON Run IB Run II RunIIBSTART PHYSICS March 2001 2003 Energy 900 1000 1000 GeV Bunches 6 36 36 Bunch length (rms) 0.60 0.43 0.18 m Typical Luminosity 1.6 1031 8.3 1031 2.0 1032 cm-2 sec-1 Integrated Luminosity* 3.2 16.7 41.0 pb-1/week Bunch Spacing 3500 396 132 nsec Interactions/crossing 2.5 2.2 5.3 (@ 45 mb)


D0

From inside out: Vertex Detector, Central Tracker, Calorimeter Solenoid Muon chambers, Toroid


ATLAS


D0

Vertex Detector (SMT): four barrel layers, 50um pitch. L1+L2 single sided, L2+L4 double sided (2deg stereo). Disk modules have 12 wedges, double sided (30deg stereo).

Central Fiber Tracker (CFT): 8 concentric layers with fibers. All doublets with 2 deg stereo angles. VLPC readout. 72k channels.

Solenoid: 2.7 m long, R=60cm, E=5MJ, B=2T. 0.9Xo dPt/Pt=0.002 Pt (combined SMT+CFT)Preshower detecor for em or had particle id.

Calorimeter: Liquid argon, 15 inter. Lengths. Resolution for jets: 80%/Sqrt(E).

Muons: 3 layers. Toroid (iron) in between L1,L2. Onne and Paul work on muon reco.


TrackingV

erte

x D

etec

tor

(SM

T):

fou

r ba

rrel

la

yers

, 50u

m p

itch.

L

1+L

2 si

ngle

sid

ed,

L2+

L4

doub

le s

ided

(2

deg

ster

eo).

Dis

k m

odul

es h

ave

12

wed

ges,

dou

ble

side

d (3

0deg

ste

reo)

.

Cen

tral

Fib

er T

rack

er

(CF

T):

8 c

once

ntri

c la

yers

with

fib

ers.

All

doub

lets

with

2 d

eg

ster

eo a

ngle

s. V

LP

C

read

out.

72k

chan

nels

.

dP

t/P

t=0.

002

Pt

(com

bin

ed

SM

T+

CF

T)


D0

Once upon a time… it all worked

RUN I, event display

•Top event from Run I


D0-Top

Top physics!


D0-Trigger

128 terms 128 terms

<50 HzL1

4 s 10 kHz10 kHz 1000 Hz1000 Hz L348ms

48 nodes

Detector. Collision rate 7MHzDetector. Collision rate 7MHz

L2100s

L2=+DetectorPreprocessors (+ Silicon Track Trigger)

Global Processor

The colliding 1 TeV proton and antiproton beam from TEVATRON lead to an enormous event rate (millions/sec), leading to the need of fast (efficient) online event selection=trigger.

The Global Processor is implemented as a fast Alpha processor on a VME card

Storage


D0-trigger

L2FW:Combined objects (e, , j)

L2FW:Combined objects (e, , j)

L1FW: towers, tracks, correlations L1FW: towers, tracks, correlations

L1CAL

L2STT

Global L2

L2CFT

L2PS

L2Cal

L1CTT

L2Muon

L1Muon

L1FPD

Detector L1 Trigger L2 Trigger

7 MHz 5-10 kHz

CAL

FPSCPS

CFT

SMT

Muon

FPD


The Muon System and Higgs discovery in ATLAS

Difficult final state: 6 jetsBackground tt + light quarks

Need good B tagging: ATLAS b=50% c=10% uds=1%

b

t

t

g

g

H

W

W

b

b

b

j

j

t

t

xfbATLAS MH=115GeVfor 100fb-1:( e or

5B

S

Muon Trigger for all channels with Z --> W --> (and: t --> bW --> b)Muon Precision Chambers for offline analysis.

Promising low mass MH<130GeV channel in this context: ttH-->bWbWbb--> jjbbbb

+ Etmiss


The Muon System and Higgs discovery in ATLAS

For higher masses MH>120GeV, H-->ZZ*-->4leptons becomes important.At MH=120 Significance=4 for 100fb-1

(need excellent mass reconstruction)

For MH>2MZ, the 4 lepton channel becomes absolutely gold-plated (60 events, background free)

PLOT????

For the high mass Higgs >150 GeV, also H-->WW-->llor associated WH-->WWW--> llllor lljj (like sign leptons)with Significance=5 for 100fb-1

DIAGRAM


Higgs discovery in ATLAS

Expected to be the discovery channel for a low mass Higgs (<150 GeV)Background: light quarks to and fakes

Another kind of interesting events: associated Higgs Production (ttH, WH, ZH , qqH), with H--> gives for 100fb-1 additional:

ATLAS for 100fb-1: (1100 events)

6B

S

tt

g

g

H

t

6B

S These channels have smaller Xsection, but smaller background, especially WH and ZH

Associated production WH and ZH with H-->bb is hopelessin ATLAS because of background. These are the most promising channels at TEVATRON.


Higgs discovery at TEVATRON (D0)

Expected to be the discovery channel for a low mass Higgs.

q W, Z

q

W, Z

Hb

b

l or

l or

Promising associated production

Need good B tagging: b=57% c=20% uds=1%Need good Mass resolution, simulation predicts 15% (with 10% mass resolution background reduced by two!!!)

Final state (MH=120, 30fb-1)

Significance

lbb 2.9

llbb 1.4

Etmiss+bb 2.6

qqbb 0.29


Higgs discovery at TEVATRON (D0)

At higher mass the decay H-->W,Z becomes important

q W, Z

q

W, Z

H

W,Z

W,Z

l or or q

Associoated production in the mass range 130-190 GeV

Final state 30fb-1

Significance

ll+ jj(Etmiss)

3

ll+ X(likesign leptons)

3


LHC vs TEVATRON

@LHC decay channel H--> and associated ttH production promising at low mass.

These channels are out of reach for TEVATRON, simplybecause of the low Xsection

@TEVATRON the associated production channels WH and ZH are most promising.

These channels are out of reach for LHC because of overwhelming (QCD) backgrounds.

NOTE:Studies by ATLAS suggest that these channels may be out of reach for TEVATRON as well.

QCD backgroundLO/NLO predictionsMass reconstructionB tagging


Proposed Improvements for D0

Silicon Vertex Detector dies after 4fb-1 ---> replace it in shutdown 2003.

Research Proposal submitted NWO by MV includes the upgrade of the level 2 trigger with an additional global processor.This will allow to include vertex information for B tagging, leading to higher Higgs discovery potentials.

Presently, we are involved in offline SVTX finding using full simulation and reconstruction packages.


Higgs Production and Decay

The strong process gg-->Higgs is the main production channel.

Electroweak (Associated) production of Z or W important, because of signature.

•Up to a mass of 140 GeV the Higgs will predominantly decay into b quarks. •Other decay modes require high luminosity (LHC)



115 GeV

115 GeV



115 GeV

t

t

g

g

H

W

W

b

b

b

j

j

t

t


Higgs Online Selection

Associated production of Higgs and Z or W is relatively easy to trigger. For example: when the Z decay to neutrinos, the event can be recognized by large missing energy (but low event rate and efficiency).

doprimaryvtx

secondaryvtx

Lxy

Single Higgs production only accessible with powerful b trigger, using tracking information.


B meson

In the offline analysis all (low mass) Higgs studies need to require B tagged jets.

We propose to introduce the B tagging already in the online event selection.


gg HWH

ZH

1.0 10000.3 3000.18 180

WZWbb

3.2 3200 11 11000

tttb+tq+tbq

7.5 75003.4 3400

QCD 106 109


Event rates


The vertex fit

The Principle


The vertex fit

Where V=Vo+

Assumption:

Then

A Closer Look

|||| PoVoPoVo

PoVoPoVE

200

2

00

00

02 ||

22

1

)(

i

ji

Ei

EE

PVij

g

g


Study events• SVTX finding algorithm

Start with (free) selected tracksSignificance>3

Start with (free) selected tracksSignificance>3

Make all possible 2-track vertices(vertex fits)

Make all possible 2-track vertices(vertex fits)

Keep/Kill vertices with shared tracks(based on probability + cuts)

Keep/Kill vertices with shared tracks(based on probability + cuts)

Try to add tracks to vertices(based on probability + cuts)Try to add tracks to vertices

(based on probability + cuts)

Select (kill) good (bad) vertices(based on probability + cuts)

Select (kill) good (bad) vertices(based on probability + cuts)

tt


Study events• Tracking

Significance wrt pv =

tt

Private X0fix

Newpropagator


Study events• Track Selection

Track cuts: remove PV tracks and demand |Significance wrt pv =

tt

Private X0fix

Private X0fix

Newpropagator


Study events• Probability and Cuts

Start with selected tracks and make all possible two-track vertices. Reject when 1<‘Direction’<3.

tt


Study events• Probability functions.

When required (for fine tuning) more variables can be included in a simple way

tt


Study events• Resolution

Bad resolution on lifetime….

tt


Results (Feb/2000)Results for standard efficiency definition (for a optimized cut on Significance)

Results for efficiency definition 2: Including all SV-track requirement.

Where dr is distance |PV - SV |

Track Efficiency Efficiency Purity SignificanceID dr<0.2 dr>0.2 cut

pythia.ttbar_mb0fix 401 17 35 71 3.0pythia.ttbar_mb1av 401 13 22 61 3.0top69= isajet 1m 1401 23 61 81 1.7top0mb 1401 11 40 62 1.2top0mb 1401 9 37 72 2.4top1mb 1401 14 43 77 1.2top1mb 1401 10 35 79 2.4

Efficiency Efficiency Purity Significancedr<0.2 dr>0.2 cut

pythia.ttbar_mb0fix 401 17 26 57 3.0pythia.ttbar_mb1av 401 12 22 54 3.0top69= isajet 1mb 1401 14 52 63 1.7top0mb 1401 9 39 49 1.2top0mb 1401 7 37 69 2.4top1mb 1401 11 36 57 1.2top1mb 1401 8 29 66 2.4


Results

Where dr is distance |PV - SV |

A tru SV is considered ‘tagged’ as + assigned tracks are from tru SV. For >2 track vertex one wrongly assigned tru PV is allowed.

122 dist

Files all gtr-mc-find by Maria Roco

Puritydr<0.2 dr>0.2 all

1 top69 standard t82 7 23 17 382 top69 standard t82 + new DistoPV 20 52 38 403 top69 standard t82 + new DistoPV + X0 fix 19 54 40 544 top69 standard t82 + new DistoPV + X0 fix + t79 GetMCDistinctVertices 25 60 46 755 top69 " + loose track-adder 27 66 50 776 top69 " + loose track-adder + parametrization of track errors (Pt) 25 55 43 577 top0mb as 5) + X0-fix 19 48 37 728 top0mb as 5) + new propagator 15 59 42 669 top0mb as 5) + new propagator + X0-fix 15 53 39 84

10 ttbar4mb as 5) + new propagator? 17 45 33 4811 bbbar1.1mbav " 1 19 5 7512 QCD, Pt>20 " 1613 zee " 0 0 0 0

B - Efficiency


Study eventstt

RECO

TRU

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