# Presentation: 444097

## Recent Results From

- G. Watts (University of Washington)

- For the DØ Collaboration

- QCD

- ElectroWeak

- Top

- Higgs

## Searches for physics beyond the SM

- Second Half of New Spring Results Presentation

- Completing the SM

- (WHWbb), (Wbb) (Zb)/ (Zj), (HWW*), Single Top

- Precision Tests of the SM

- d/dpT, d/dMjj, Azimuthal Jet Decorrelations, (tt)

- (W), (H), (hbb)

- New Phenomena and B Physics – see talk by A. Nomerotski on March 26th...

## Winter Conference Dataset

- Thanks to all for the data!

- All Data Reprocessed by December 2003 with improved reconstruction

- ~170 pb-1 for these analyses

## W Cross Section

- Trilinear Gauge Couplings

- e channel: 162.3 pb-1
-  channel 82.0 pb-1

- Small in SM
- Sensitive to new Physics

- W pT and MW

- _Signature_

- e or  and 
- and  photon

- _Primary Background_

- W+Jets, jet fakes a .

## W Backgrounds

- W Backgrounds

- W+Jets

- Jet fakes a photon
- Determine photon fake rate from data
- 0.3% - 0.1 % for 10 GeV to 50 GeV jets

- Use sample of events with good electron and apply tracking efficiency.

|  | e |  |
| --- | --- | --- |
| W+Jets | 80.0 ± 7.4 | 31.0 ± 10 |
| leX | 3.7 ± 0.5 | 0.6 ± 0.6 |
| Z | - | 4.7 ± 2.0 |
| W  | 3.4 ± 1.1 | 0.9 ± 0.3 |
| Total | 87.1 ± 7.5 | 37.0 ± 10 |

- Expected Background Event Counts

- leX

- Lepton + electron with out track + missing ET

- tt, etc.

- Z, ’s

- MC based

## W Results

- With increased data detailed W kinematic studies will be possible

- Signal Eff calculated using Baur MC + Pythia

|  | We | W |
| --- | --- | --- |
| Background Expected | 87.1 ± 7.5 | 37 ± 10 |
| Observed | 146 | 77 |

- (ppWl+X)
- 19.3 ± 6.7 ± 1.2(lumi)

- First Step...

## QCD Inclusive Jet and Dijet Cross Sections

- Run 2 Datasets

- Better discrimination of PDFs

- Traditional place to search for new physics

- Quark Compositeness, etc.

- Reliable Test of NLO Perturbative QCD

- Jet Evolution, Parton Distribution Functions, new physics at s.

- Look at both Forward and Central Regions

*Central Region* – large transverse energy – most sensitive to new physics and PDFs
*Forward Region* – Less sensitive to new physics, but still sensitive to PDFs

- Jet Energy Scale is largest systematic error

## d/dpT

- Similar, with larger errors, for other eta regions

- Central

- Far Forward

- Forward

- Central

- Stay tuned for improvements to JES

## Mjj

## The “Biggest” QCD Event

## Jet Azimuthal Decorrelations

- Leading Order pQCD

- Jets are back-to-back

- 3 jets in pQCD

- 12 = 

- 12 < 

- 12 is sensitive to jet formation without having to measure 3rd jet directly!

**Notes:**
Hard physics to soft physics test

## Jet Azimuthal Decorrelations

- Look at events with 2 jets

- Measure dijet

- Compare to a LO & NLO MC

- 2

- 1

- 1

- 2

- LO MC 3 jet production has pole as pT3 -> 0

- LO MC 3 jet dijet > 2/3

- Not compatible with a LO description

## Jet Azimuthal Decorrelations

- ISR rate in MC has strong effect on matching as well.

- Further tests of MC Model

- Important for tt, H mass, etc.

- More data, better JES will continue to improve the power of this measurement.

## Non SM H  

- Z/y ee – (data)
-  production (MC)
- QCD w/jets misidentified (data)

**SM H ******** ******

- Branching Ratio is small, 10-3, 10-4.

**Beyond SM Suppress Higgs Products**

- Fermiphobic or Top Color Higgs

- BR(H  ) enhanced

- Backgrounds

- Require 2 isolated EM Objects
- pT>25 GeV

## Non SM H  

- Look for resonance in M

- Split the detector by regions according to fake rates

|  | Data | Total BKG | QCD | DY | gg |
| --- | --- | --- | --- | --- | --- |
| CCCC | 93 | 54.4 ± 28.0 | 42.7 ± 28.0 | 1.4 ± 1.3 | 8.3 ± 0.6 |
| CCEC | 97 | 68.8 ± 45.8 | 64.0 ± 45.7 | 3.0 ± 3.0 | 1.8 ± 0.1 |
| ECEC | 41 | 20.8 ± 10.4 | 13.1 ± 10.0 | 6.7 ± 3.0 | 1.0 ± 0.1 |

- None found, so set limits...

- Systematic Errors

- Dominated by Luminosity determination
- And photon fake rate determination

## Non SM H  

- Fermiophobic model from A. G. Akeroyd, Phys Rev. Lett. 368, 89 (1996)

- (topcolor) Mh (GeV)

- Analysis improvements possible by making use of CPS, etc.

## Tagging a B

**B**

**Impact Parameter (d)**

**Impact Parameter Resolution**

**d/********(d)**

**Vertex Tagging a B**

**Decay Lengh (L****xy****)**

**Decay Length Resolution**

**L****xy****/********(L****xy****)**

**Hard Scatter**

**Top, Higgs contain b-quark jets**
**Most backgrounds do not**
**Leptons from B meson**
**Contain a B meson**
**Has finite life time**
**Travels some distance from the vertex before decaying**
**~ 1mm**
**With charm cascade decay, about 4.2 charged tracks**

- Several algorithms under active development

**Notes:**
This slide might need some reworking. Perhaps find a better picture of how the tracking works (or draw a schmatic). Split the inner vs outter discussions up into two slides – this is something anyone can deal with, I think.

## CSIP Algorithm

- Counting Signed Impact Parameter

- S(IP) = IP/(IP)

- Based on Impact Parameter Significance

- Jet axis

- Track

- I.P

- 

- Primary vertex

- 40%

- Light Quark Fake Rate

- 0.5%

**Requirements to tag a jet:**
-   - at least 2 tracks with S(IP) > 3
-   - or at least 3 tracks with S(IP) > 2

- Per Taggable Jet Rates Measured in Data!

## JLIP Algorithm

- Jet Lifetime Impact Parameter

- Based on Impact Parameter Significance

- Probability distributions
- P(Track from PV)
- Defined for each class of tracks
- # of SMT Hits, pT, etc.

- Each jet assigned P(light quark)

- Light Quark Fake Rate

- 40%

- 0.5%

## Slide 20

## SVT Algorithm

- Z axis

- Secondary Vertex Tagger

- Reconstruct Vertices using displaced tracks

- S(Lxy) = Lxy/(Lxy).

- Cut on Decay Length Significance

- 40%

- 0.5%

## B Tagging

- Performance on signal

- tt lepton+jets ~ 56%
- Single Top (s channel) ~ 52%
- Wbb ~ 52%
- Wj ~ 0.3%

- Combining the Taggers

- Already studied the correlations
- Working now on making a combination

## Higgs Production at Large tan

- Higgs Production at Large *tan***

- Low *tan ****, *→ Standard Model Higgs
- High *tan ****, *→* *enhanced* **bbH*
- Cross section rises like*** tan******2*********
***Substantial improvements in Theory understanding since Run 1***

*~tan ***

- MSSM

- Use 3 b-tags

- Backgrounds Include:

- QCD: bbh, bbjj, bbbb
- EW/St: Zb, Z, tt

- Look for excess in di-jet mass window

- 4 Jet HF MC QCD not well tested: design around its use

- Use shoulders to calibrate

***CP-odd Higgs******Production***

***CP-even Higgs******Production***

## Higgs Production at Large tan

- L=130 pb-1

- Background shape determined from data

- Normalization determined by fitting to region ±1 from expected higgs signal

- Look for Mass Resonance

- 3 Jets In Event
- 20, 15, 15 GeV

- Trigger on 3 jets +
- ~60% efficiency

## Results

- Set limit using fitted distributions (TLimit)
- Will be down at 40 with MA=100 at 1.6 fb-1
- No analysis improvements taken into account!

- Search for SUSY Higgs at high tan 

## Higgs Decays

*High Mass Higgs Searches*

*Low Mass Higgs Searches*

- Nominal Mass Reach Spans Two Decay Modes

- Search strategies are a function of Decay Channel and Production Channel

- HDECAY

- MH[GeV/c2]

- Excluded

**Notes:**
What are the uncertainties in the HDECAY calculation here? Turns out this really depends upon the inputs to the HDECAY program. If you look at how you are supposed to run it, you would not expect anything there.

## Higgs Production

- No Good at Low Mass

- Overwhelmed by QCD background

- Good at High Mass

- Good at Low Mass

- Gluon Fusion

- Associated Production

- M. Spira; NLO

## Wbb, electron channel

- Same final state as WH
- One of background processes
- Event selection include
- Central isolated e pT > 20 GeV
- Missing ET > 25 GeV
- ≥ two jets: ET > 20 GeV, || < 2.5
- 2587 evts. in Lint=174 pb-1 of data

- Fair understanding of data

- Simulations with Alpgen plus Pythia through detailed detector response
- Cross sections normalized to MCFM NLO calculations

## Wbb, B Tagging

- Fair agreement

- Observe 8, expect 8.3±2.2

- Add a MT window cut for the W (25-125 GeV)

- Observe 5 events, expect 6.9±1.8

- (Wbb) < 20.3 pb
- Prefer Wbb at 2

- Top is principle background!

## Wbb, B Tagging

- Require NJ = 2

- Observe **2 evts**, expect **2.5±0.5**

- Suppress Top Production

| Wbb | Wc(c) | Wjj | tt+t | Others |
| --- | --- | --- | --- | --- |
| 1.4±0.4 | 0.3±0.1 | 0.1±0.03 | 0.6±0.2 | 0.1±0.03 |

- Require All Three Tagging Algorithms

- Observe **2 evts**, expect **0.3±0.1**

- Expect 0.6±0.2 from Wbb

- SM with no Wbb disfavored at 2 level

## WH Limits

| Source | Uncertainty
 (%) |
| --- | --- |
| Jet energy scale | 14 |
| Jet ID | 7 |
| b-tagging | 11 |
| Trigger & e ID | 5 |
| EM scale | 5 |
| MC simulations | 15 |
| Total | 26 |

- (WH)B(Hbb) < 12.4 pb
- (MH = 115 GeV/c2)

- For WH limit use mass window. Expect 0.03 WH, 0.54 from SM backgrounds, observe 0

- Add mass window cut
- 85-135 GeV/c2

- @ 95% C.L.

**Notes:**
For the WH limit:
We have optimized the mass window on s/sqrt(B) on simulation, 
we get 85-135 (i.e. 110+-25), and in that window 
we expect 0.03 +- 0.01 evts compared to 0 data and 0.54+-0.14 from 
SM (mainly Wbb, single top, ttbar).
you might want to write down these numbers below the bottom table.
(like 0.03 WH expected, 0 observed, 0.54 expected from SM in mass w.).

## 3 views of  high dijet  mass (220 GeV) Wbb (WH) candidate

**Vertex view of 2nd candidate**

**3 views of  high dijet  mass ****(220 GeV)**** Wbb (WH) candidate**

**dijet  mass  (48  GeV)**

** ****E****T****miss**

## Z(ee/)b

- Background to ZH production
- Benchmark for SUSY Higgs production via gbbh
- Probes PDF of the b-quark

- Measure cross section ratio
******(Z+b)/********(Z+j)**
- Many uncertainties cancel

- Isolated e/m with pT > 15/20 GeV, || < 2.5/2.0
- Z peak for signal, side bands for bkgd. evaluations
- Jet ET > 20 GeV, || < 2.5
- At least one b-tagged jet

- L=184 (ee), 152 () pb-1

- Jet Flavor Content Calculated with MCFM (NLO)
- b/c Ratio

- Background

- QCD and Z/

## Z(ee/)b

- Z(ee/)b

- Clear Indication of Heavy Flavor

- Good Match to MC

- QCD and mistag bkgd. estimated from data

- Zb normalized to data

- Tag required

## J. Campbell, R. K. Ellis, F. Maltoni, S. Willenbrock

| Source | Uncertainty
 (%) |
| --- | --- |
| Jet tagging | 16 |
| Jet energy scale | 11 |
| Bkgd. estimation | 6 |
| (Z+c)/(Z+b) | 3 |
| Total | 20 |

- Theory

- hep-ph/0312024

- R~0.02

## H  WW(*)  l+l-

- H  WW(*)  l+l-

- Event selection include
- Isolated e/
- pT(e1) > 12 GeV, pT(e2) > 8 GeV
- pT(e/1) > 12 GeV, pT(e/2) > 8 GeV
- pT(1) > 20 GeV, pT(2) > 10 GeV
- Missing ET greater than
- 20 GeV (ee, e); 30 GeV ()
- Veto on
- Z resonance
- Energetic jets

- High Mass SM Higgs Search

- L = 180 (ee), 160 (e) and 150 () pb-1

- Channel

## H  WW(*)  l+l-

**Higgs of 160 GeV**

- Spin Correlations

- (ll) – Azimuthal Angle

- QCD

- Z

- Leptons from Higgs Tend to be collinear

- Can’t reconstruct mass due to presence 2 neutrinos

| WW | W+jets | WZ | tt |
| --- | --- | --- | --- |
| 2.51±0.05 | 0.34±0.02 | 0.11±0.01 | 0.13±0.01 |

## H  WW(*)  l+l-

- Signal acceptance is ~ 0.02 – 0.2 depending on the Higgs mass/final state

|  | ee | e |  |
| --- | --- | --- | --- |
| Observed | 2 | 2 | 5 |
| Expected | 2.7±0.4 | 3.1±0.3 | 5.3±0.6 |

- After all Cuts

-  X BR

- 95% CL

- e

## Top Quark

- Run 1 World Average Top Mass

- Run 2 Cross Sections

- All jets, dilepton, l+jets

- Precision Measurement in Run 2

- Cross Section

- Cross Check SM with MTop
- “Rare” Decays

- Mass

- Constrain MHiggs

- Stay tuned for ’s

## Di-Lepton Top Cross Section

- Small cross section
- Relatively free of SM backgrounds

- SM Backgrounds

- ALPGEN+Pythia

- Instrumental Fakes

- Fakes

- Isolated Lepton Fakes

- Estimated on data

## Cuts

- ee

- 

- e

## Dilepton Cross Section

## Dilepton Cross Section

- Cross section shows some excess which is still consistent with the standard model expectation. We are looking forward to collecting more data!!

## Lepton + Jets

- Fit shapes from likelihood discriminate of signal and background

- 1

- Preselection cuts removes all but W+Jets

- 2

- Determine Topological Variables

- No B-tagging

- 3

- Create Likelihood Discriminent

- 4

- Fit data to combinations of backgrounds and signal

- Preselection Cuts include NJets>=4, etc.

- Systematics Driven Method

- LP’03 results were close to being systematics driven

## Lepton + Jets

- Topological Variables

- Good S:B
- Minimize JES
- Small Correlations

- Sphericity

- Aplanarity

- HT2/HZ

- KTmin

- HT2/HZ

- Centrality
- HT of all but leading jet

- KTmin

- KT of #4 jet relative to #3 jet.

## Lepton + Jets

## Lepton + Jets

- Total

- +Jets

- e+Jets

## All Jets Cross Section

- 46% of ttbar production

- QCD is many orders mag greater

- Simple Cuts aren’t enough!

- 6 Jets, exactly one btag

- Background Rejecting NN

- Top Hypothesis NN

- Cut

- Cut

- Top Quantity NN

- NN are trained on data for background, and ttbar MC for signal

- HT,H3jT,<Nj>, sphericity, aplanarity, centrality

- ET4,5, average eta

- ww, tt, MWW, Mtt, Mmin1,2, Mmin3,4

## Discriminating Variables

- Variables are designed to address different aspects of the background
- Energy Scale – HT, sqrt(s)
- Soft non-leading Jets – H3jT, ET5,6,<Nj>
- Event Shape – Sphericity, aplanarity
- Rapidity – Centrality, <2>
- Top Properties – Top and W Mass Likelihood, MWW, Mtt, min dijet masses

- Background model is data-derived

- JES Systematics

## All Jets Cross Section

- 0.75

- 220 events pass all cuts
- Expect 186 ± 5(stat) ± 7.5(sys)

|  | Uncertainty
(%) |
| --- | --- |
| Vertex ID | 1 |
| Jet ID | 10 |
| JES | 28 |
| Jes Resolution | 0.6 |
| Top Mass | 7.6 |
| Trigger | 4 |
| Tagging | 4.0 |
| Total | 31 |

## Slide 52

## Top Mass Combination

- DØ New Run I Top Mass Result is now part of the TeV MTop combination

- (see Juan’s April 25 2003 W&C)

- Old Combination Mt = 174.333 ± 5.141

- LEP EWWG

## Really want to talk about...

- (Old TeV Top Mass)

- Squeezing Run 2 Top and W Mass Errors

- Extensive program in place

- Coming to a Wine And Cheese near you soon...

## W/Z Cross Sections

- Analyses in Progress

- Not updating cross sections this time around, but we have a new sample and new analysis in advanced state of review

## Forward Proton Detector

- 9-17 mm from beam @ 30 m
- 0.92 < t < 3 GeV2 @1960 GeV

- Installation is Complete!

- Analysis in progress
- dN/dT, diffractive jets

## Single Top

- Single Top Production gives you access to
- B(tWB)
- |Vtb|
- W Helicity
- Top Polarization
- Top Width
- Anomalous couplings
- Rare Decays

- Preselect Events

- Apply BTagging

- Apply Topological Cuts

- QCD (fakes)
- W+Jets
- ttbar

- Backgrounds

- (MC)

- (Data)

- (Data)

- +jets/SVT

## Expected Sensitivity

|  | SLT | SVT | JLIP | SLT | SVT |
| --- | --- | --- | --- | --- | --- |
| s-channel | 0.67 0.14 | 1.87 0.46 | 1.88 0.46 | 0.63 0.13 | 1.38 0.35 |
| t-channel | 0.95 0.20 | 3.14 0.76 | 3.20 0.82 | 0.88 0.19 | 2.19 0.56 |
| tt | 9.60 1.65 | 23.31 4.90 | 24.50 5.48 | 8.43 1.44 | 18.57 3.75 |
| non-top | 31.1 5.2 | 63.5 12.3 | 71.7 13.7 | 34.3 5.1 | 67.0 11.8 |
| Total expected | 42.4 5.4 | 91.9 13.3 | 96.3 14.8 | 44.2 5.3 | 89.2 12.4 |
| Observed | 49 | 88 | 99 | 48 | 94 |

|  | Without Systematics | With Systematics |
| --- | --- | --- |
| s (pb) | <6.4 | <13.8 |
| t (pb) | <9.0 | <19.8 |
| s+t (pb) | <7.9 | <15.8 |

- Expected Limit!

*We have not applied final topological cuts yet!*

- Already better than Run 1 limits!

- Electron Channel

- Muon Channel

## Conclusions

## Conclusions

- Taking advantage of the Data
- QCD program is under way with jet cross sections and studies.
- Electro weak is moving to the next level of accuracy
- Higgs is demonstrating an understanding of the most important backgrounds
- Top has remeasured the cross section.
- Mass result will appear soon.
- Many new analyses and conference results.
- More in the pipeline!
- Write-ups available for all analyses
- Improvements On Tap
- JES
- Already have another 70 pb-1 on tape.
- New Ideas...

## Slide 61

## Jet Cone Algorithm

## Jet Cone Algorithm

## Dilepton Event

## Multi-jet Background

- Full Multijet
- Sample

- 2-Tagged Sample

- Calculate TRF
- (pT & 3 Regions of )

- Apply TRF

- 3-Tagged Jet
- Distribution

- Fit outside to real 3
- Tagged Distribution

- bbbb, zbb

- Shapes are similar, so fit should take care of them to first order

- Fitted Background