April 14, 20041

Physics with Muons: DØ Highlights

Exciting new results from analyses presented at Moriond 2004 on B Physics New Phenomena searches Electroweak & Top StudiesIntegrated Lum’y up to 250 pb-1

With emphasis on the strategy brought on because of the muon system.

Tom Diehl (FNAL)For D0 Collaboration

No Shielding

D0 Shielding

0 10 20

D0 Interaction lengths

April 14, 20042

Acknowledgements

Special thanks to S. Burdin, A. Nomerotski, J. Stark, G. Watts, M.

Verzocchi, and R. Kehoe for discussions and for many of the slides.

April 14, 20043

SMTSMT

SMT

Muon System and Tracker New muon system with ||<2 and good shielding 4-layer Silicon and 16-layer Fiber Trackers in 2 T magnetic field

April 14, 20044

Properties of a Good B Physics Detector*

* From “B Physics @ the Tevatron: Run 2 and Beyond” A high precision vertex detection Tracking w/ excellent momentum resolution Excellent particle ID capability Robust trigger integrated into a high bandwidth DAQ

No specific mention of importance of muons?

April 14, 20045

Properties of a Good B Physics Detector*

* From “B Physics @ the Tevatron: Run 2 and Beyond” A high precision vertex detection Tracking w/ excellent momentum resolution Excellent particle ID capability Robust trigger integrated into a high bandwidth DAQ

The point is, muon trigger and ID is only one of several required elements.

(BUT it turns out to be most advantageous to have powerful muon trigger and ID. Trigger on: J/ and/or

a tagging lepton. No Lifetime cuts in trigger.)

April 14, 20046

J/: Run 1 vs. Run 2

Run I: 407 62 J/ 6.6 pb-1 out of 13 pb-1

pT()>8 |eta()|<1 ~35% from B’s (1/p)= 0.18/p2 + 0.003

Run II: 1.2M J/ 250 pb-1

pT()>0.18 |eta()|<2ish [(pT)/pT]2 ~ 0.0152 + (0.0014pT)2

April 14, 20047

Why so many J/psi in Run II?

pT() of J/psi in B-decays Monte Carlo

16% have 2 pT >1.5 GeV/c 7% have 2 pT > 1.5 & 1

pT > 3.5 GeV/c 0.1% have 2 pT > 6.0 GeV/c

It’s the trigger that gets them onto tape.

It’s the solenoid & tracking that provides the skinny peak.

pT() (GeV/c)(G

eV/c

)pT

()

Run 1

April 14, 20048

Tracking Performance

pT spectrum of soft pion candidate in D*D0

Tracks are reconstructedstarting from pT = 180 MeV(Lower pT is better)!

Muon in J/psi events

Coverage of Muon system is matched by L3/offline tracking

“This greatly enhances our B-physics program.” - A.N.

Lower trig threshold in magnet corner

Data

April 14, 20049

Tracking Performance

Impact Parameter Resolution

NOT yet used for PIDP/K/ separation for some pT

SMT dE/dx

More tracking improvements under way

• (DCA) 16 m @ PT = 10 GeV (DCA) 54 m @ PT = 1 GeV• Resolution compares well with MC

April 14, 200410

X(3872) J/ + -

Last summer, Belle announced a new particle at 3872 MeV/c2, observed in B+ decays:B+ K+ X(3872), X(3872) J/ + -

Nature of X(3872) is not known• could be charmonium, meson molecule etc.

Belle’s discovery has been confirmed by CDF and DØ.

300 61 events, a 4.4 bump

(2S) (1S) w/ br (31%)M[(2S)] M[(1S)] = 589 MeV/c2

Compared properties of sample of X particles to sample of (2S): no differences seen in pT, d.l., isol, …

M = 0.7680.004(stat)0.004(syst) GeV/c2

April 14, 200411

Exclusive B Decays

Accumulated large exclusive samples of B+ and B0

Find in 250 pb-1:B+ J/K+ 4306 events

B0 J/K* 1900 events

B0 J/Ks 375 events

b J/ 52 events

Mb=5615 9 MeV/c2

Good S/B Lifetime cuts applied

lxy/(lxy)>4.5

April 14, 200412

The world largest sample of exclusive Bs J/ decays

Work in progress on Lifetime measurements Studies of Mixing & CP effects

Bs Exclusive Decays

250 pb-1

Some lifetime cuts applied

Bs Ds (

Bd D+ (

GeV/c2

Work in progress on Bs/Bd lifetime ratio and first results on Bs mixing

• need to fully understand time resolution

• if ms 15 ps-1 expect a measurement with 500 pb-1

+ cc

April 14, 200413

Semileptonic Bd sample

Collected by low pT single muon triggers

109k B+ D0 candidates 25k B0 D* candidates

D* yield 50% higher for looser selections

Plots below have (offline) lifetime cuts

Sample compositions:

“D0 sample”: 82% from B+ “D* sample”: 86% from B0

Estimates based on measuredbranching fractions and isospinrelations.

B D0 X

April 14, 200414

(B+)/(B0): Result

one example : VPDL bin [0.10 - 0.15 cm]

Preliminary result:(B+)/(B0) = 1.093 0.021 (stat) 0.022 (syst)

(among the most precise of this quantity)

Use binned c2 fit of event ratios to

determine (B+)/(B0)

VPDL=LT/pT(D0)*Mb

April 14, 200415

B0

B0/B0 Mixing: Milestone !

Preliminary results:

md=0.5060.055(stat)0.049(syst) ps-1

Tagging efficiency: 4.8 0.2 % Tagging purity: 73.0 2.1 %

Tagging procedure• opposite side tight muon • muon pT > 2.5 GeV/c• cos < 0.5

Fit procedure• Binned 2 fit

• Already one of the best measurements at hadron collider • Good prospects to improve accuracy

• work in progress to decrease systematic uncertainty• use other tagging methods: jet charge, same side tagging, electron tagging• add more D0 decay channels

April 14, 200416

Observation of B D** X

• Start from B D*X sample, add another +

• Look at invariant mass of D*- + system• Observed merged D1

0(2420) and D2*0(2460)

Two interfering Breit-Wigner D** states with mass/width as measured by Belle (no resolution effects included) Work in progress: extract separate amplitude for each state and relative phase of interference

wrong-sign combinations

Unique observation at hadron colliderPreliminary result on product branching ratio

Br(B {D10,D2*0} X) Br({D1

0,D2*0} D*+ -) = 0.280 0.021 (stat) 0.088 (syst) % measured by normalizing to known Br (B D*+ X)

D** are orbitally excited D meson states

April 14, 200417

Properties of a Good High pT Muon Detector

High pT > 10 GeV/c e.g. Top Pairs

Most high-pT physics is centralish

Don’t need to cover past ||=2

TTbarbb

Moderate Coverage

Low Background

The Physics is cross-section limited Require a robust high-pT unprescaled trigger. Rejection against low pT muons, cosmics, meson in-

flight decay.

Accep’ for both muons

April 14, 200418

W & Z to Muons in Run 1

13 pb-1 (Run 1a) 1665 W’s 77 Z’s

Muons + jets or EM was much better off at trigger level.

April 14, 200419

W and ZCross Sections

Zin 117 pb-1. 2 opposite-charged tracks w/

pT>15 GeV/c At least one is isolated Scintillator timing, DCA,

acolinearity cuts to remove small backgrounds

In 150 pb-1 we have ~ 15,000 of these due to improvements in the trigger. In 250 pb-1…

Testing our understanding of the systematics (Update soon).

# E

vent

s \ n

s

Br = 261.8 ± 5.0 (stat) ± 8.9 (sys) ± 26.2 (lum) pb(prior to reduction in L)

Cut at 16 ns

117 pb-1

6126 events

April 14, 200420

W and ZCross Section

Win 17.3 pb-1. An isolated muon w/ pT>20

GeV/c in ||<1.6

Bkgd is Z, WQCD Veto if additional muons. F(bkgd.)=0.118

8305 Candidates after background subtraction

In 104 pb-1 we have ~73,000 WIn 250 pb-1…

Br = 3226 ± 128 (stat) ± 100 (sys) ± 322 (lum) pbR is high in these early results.

April 14, 200421

W Cross Section:

Small cross section in SMSensitive to new Physics

Signaturee or and and photon w/ (ET>8 GeV) & R(l>0.7)

We W

Luminosity (pb-1)

Background Expected

Bkgd + SM Signal Expected (events)

162

87.1 ± 7.5

142 ±17

82

37 ± 10

67 ±13

Observed (events) 146 77

A First Step to Trilinear Gauge Couplings

(ppW l+X)19.3 ± 6.7 ± 1.2(lumi)

pb

April 14, 200422

New Phenomena Searches SUSY

Search for Squarks and Gluinos in the Jets+MET Topology Search for mSUGRA SUSY in the Like-Sign Muon ChannelSearch for Chargino/Neutralino in ee(+l) Final State Search for Chargino/Neutralino in Trilepton Final StateSearch for GMSB SUSY in Di-photon Events with Large MET

LeptoquarksSearch for the First Generation Leptoquark

Extra DimensionsSearch for LED in Jets+MET Topology Search for Large and TeV-1 ED in Di-electron Channel LED in Di-electron and Di-photon Channels

Z’Search for Heavy Z' Bosons in Di-electron Channel

HiggsHWWdileptonsHSearch Submitted to PRL (First D0 Run II Publication)

SM is safe for another day

April 14, 200423

Top Quark

Run 1 World Average Top MassRun 2 Cross Sections

All jets, dilepton, l+jets

Precision Measurement in Run 2

Top Cross SectionsCross Check SM with MTop

Single topRare Decays

Top MassConstrain MHiggs

+ soft muon tags

April 14, 200424

Di-Lepton Top Cross Section

Lore: “Small cross section.Relatively free of SM backgrounds.”

SM Backgrounds

jjllWW jjllZ /

ALPGEN+Pythia

Instrumental Fakes

TE FakesIsolated Lepton Fakes

Estimated on data

Working on optimizing the selection criteria

April 14, 200425

Lepton + Jets

April 14, 200426

Top Cross Section Summary

Leptons + jets

April 14, 200427

Run 1 Top Mass Combination

DØ New Run I Top Mass = 180.1 ± 5.3 GeV/c2

(see Juan Estrada April 25 W&C)

“Old” Mt was 174.333 ± 5.141 GeV/c2.Role for muon is to trigger & ID (low background).

April 14, 200428

Summary/Conclusions

Details on all recent results can be found at http://www-d0.fnal.gov/Run2Physics/WWW/results.htm

B-physics at DØ is online* with world class results X(3782) seen Record semileptonic & exclusive B samples B Mixing & a precise measurement of B+/B0 lifetime ratio

High pT physics W, Z, & WCross Section and big samples in the can top cross section at 1960 GeV & Run 1 Mass

The powerful muon detector and trigger is a key contributor.

April 14, 200429

Back-up slides&

Unused slide storage

April 14, 200430

Winter Conference Dataset

Thanks to all for the data!

Thanks to all for the data!

All Data Reprocessed by December 2003 with improved reconstruction

~170 pb-1 for these analyses

April 14, 200431

LAr in gap 2.3 mm

Ur absorber

Readout CellCu pad readout on 0.5 mm G10 with

resistive coat epoxy

Drift time ~430 ns

North End CapSouth End Cap Central Cal.

ICD

EM

FH

CH OH

MH

IHEM

MG

FPS

CalorimetersCalorimeters

• Liquid Argon sampling• uniform response, rad. hard, fine spatial segmentation• LAr purity important

• Uranium absorber (Cu/Steel CC/EC for coarse hadronic)• nearly compensating, dense compact

• Uniform, hermetic with full coverage • || < 4.2 ( 2o), int ~ 7.2 (total)

• Single particle energy resolution• e: /E = 15% / E 0.3% : /E = 45% / E 4%

50k readout cells (< 0.1% bad) Fine segmentation 5000 pseudoprojective towers ( 0.1 0.1 ) 4 EM layers, shower-max (EM3): 0.05 0.05 4/5 Hadronic ( FH + CH )

L1/L2 fast Trigger readout 0.2 0.2 towers Fully commissioned

April 14, 200432

Triggers for B physics

Robust and quiet single- and di-muon triggers Large coverage |<2 Variety of triggers based on

L1 Muon & L1 CTT (Fiber Tracker) L2 & L3 filters

Typical total rates at medium luminosity (40 1030 s-1cm-2) Di-muons : 50 Hz / 15 Hz / 4 Hz @ L1/L2/L3 Single muons : 120 Hz / 100 Hz / 50 Hz @ L1/L2/L3

Rates before prescaling: typically single muon triggers are prescaled or/and used with raised pT threshold at L1

Muon purity 90% - all physics! Current total trigger bandwidth

1600 Hz / 800 Hz / 60 Hz @ L1/L2/L3

B-physics semi-muonic yields are limited by L3 filters and L3 bandwidth

April 14, 200433

Observation of B D** X

Figure from Belle, hep-ex/0307021D10, D2*0 have been observed and studied

in several experiments, most recently by BaBar and Belle in B- D**0 -

We study D10, D2*0 produced in semileptonic B decays.

D** are orbitally excited D meson states, see diagram

In heavy quark limit expect two sets of doublet states Two broad (decay through S-wave) Two narrow (decay through D-wave)

Narrow D** D0

1(2420) -> D*+ -

D*02(2460) -> D*+

-

One of decay channels

April 14, 200434

End Back Up Slides