# Presentation: 526723

## Electroweak Physics and Searches for New Physics at CDF

**Electroweak Physics and Searches ****for New Physics at CDF**

- Beate Heinemann
- University of Liverpool
- Mini-Symposium on CDF @University of Chicago
- 5th of March 2004

## The Standard Model of Particle Physics

- Electroweak SU(2)xU(1): W, Z, γ
- Strong SU(3):                  g
- Symmetry breaking caused by Higgs field
- Generates Goldstone bosons
- Longitudinal degrees of freedom for W and Z
- 3 massive and one massless gauge bosons
- -Standard Model survived all experimental challenges in past 30 years!
-       -electroweak and QCD precision data
-       -No New Physics despite many efforts!

| Particle | Mass (GeV/c2) | Force |
| --- | --- | --- |
| Photon (γ) | 0 | Electroweak |
| W± | 80.450 | Electroweak |
| Z0 | 91.187 | Electroweak |
| Gluons (g) | 0 | Strong |

- Gauge Bosons

- Higgs Boson

- Vacuum quantum numbers (0++)
- Couples to mass
- Mh  = ?

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Why not the Standard Model?

- Radiative corrections to Higgs mass: electroweak scale (100 GeV) much much lower than Planck Scale (1019 GeV): “hierarchy” or “naturalness” problem
- No unification of forces at any scale
- Higgs boson not yet found: is it there?
- No explanation for matter/ anti-matter asymmetry in universe
- No accounting for dark matter in universe
- Many free parameters, e.g. masses of all particles: unsatisfactory

- WMAP satellite

- U(1)

- SU(2)

- Coupling constants

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Supersymmetry (SUSY):
Each SM particle has a “super”-partner with same quantum numbers apart from spin (top <-> stop, photon <-> photino, etc.)
Masses are O(1 TeV)
Unification of forces at GUT scale (1016 GeV)
Hierarchy problem solved
Extra Dimensions
String theory: links gravity to other forces
Could be large (0.1mm): probed at TeV scale
Hierarchy problem solved
The unexpected...

- Each SM particle has a “super”-partner with same quantum numbers apart from spin (top <-> stop, photon <-> photino, etc.)
- Masses are O(1 TeV)
- Unification of forces at GUT scale (1016 GeV)
- Hierarchy problem solved
- Extra Dimensions
- String theory: links gravity to other forces
- Could be large (0.1mm): probed at TeV scale
- Hierarchy problem solved
- The unexpected...

**What could be Beyond the SM?**

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Supersymmetry Intro

- SM Fermions              Boson Superpartners
- SM Bosons                 Fermion Superpartners
- Physical SUSY sparticles: *neutralinos (Higgs, Photon, Z partners), charginos  (Higgs, W partners), squarks  (quark partners), sleptons  (lepton partners) *
- Different SUSY models:
- Supergravity: SUSY broken near GUT scale
- GUT scale parameters: scalar mass m0 , gaugino mass m1/2 , ratio of Higgs v.e.v’s  tan*β*, Higgs mixing parameter μ
- LSP is neutralino **χ****0** or sneutrino **ν**
- Gauge-mediated models (GMSB): SUSY broken at lower energies – breaking scale F an important parameter.
- Gravitino G is the LSP (NLSP **χ****0**** →G****γ** )
- If “R-Parity” conserved:
- SUSY particles can only be pair-produced
-  Lightest SUSY Particle (LSP) stable and escapes detection
- If conserved: LSP stable, carries away missing ET

**~**

**~**

- ~

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Searches for New Physics: Strategy

- Establish good understanding of data in EWK/QCD physics in Run 2:
- Backgrounds to new physics searches
- Indirect sensitivity to New Physics
- Gain understanding of detector
- Search for as many signatures as possible, involving:
- High Pt leptons
- Large imbalance in transverse momentum (e.g. due to neutrino or neutralino)
- High Et jets
- High Et photons
- Rare decays of charm- and bottom-mesons
- Interpret:
- Provide cross section limits and acceptances (try to be as generic/model-independent as possible) applicable to future models!
- In context of specific models of physics beyond the SM

**Higgs**

**?**

**WW, W****γ****, Z****γ****,**** **

- Cross Sections (fb)

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

##  The Tevatron: Run 2

- Data
- Recording
- Efficiency

- 90% efficiency

- Expect 2 /fb by 2006 and 4.4-8.6 /fb by 2009
-  sensitivity to New Physics improved by>5 compared to Run 1

-  Run 2 started in June 01:
- CMS energy 1.96 TeV
- Delivered Lumi: 400/pb (run 1 was 110/pb)
- Promising slope in 2004!
- Data taking efficiency about 90%!
- Physics Analyses:
- Use about 200/pb taken between 03/02 and 09/03

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

##   The CDF 2 Detector

-   The CDF 2 Detector

**New for Run 2**
- Tracking System
- Silicon Vertex detector (SVX II)
- Intermediate silicon layers (ISL)
- Central Outer tracker (COT)
- Scintillating tile forward calorimeter
- Intermediate muon detectors
- Time-Of-Flight system
- Front-end electronics (132 ns)
- Trigger System (pipelined)
- DAQ system

**Retained from Run 1**
- Solenoidal magnet (1.4 Tesla)
- Central Calorimeters
- Central Muon Detectors

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Outline

- W and Z production
- Establish understanding of detector
- Alternative luminosity measurement
- Test NNLO QCD calculations
- Wγ, Zγ and γγ production
- Anomalous triple gauge couplings
- SUSY?
- High mass di-leptons
- New physics: Z’, RS gravitons, etc.
- Di-leptons + Di-jets
- Leptoquarks, Squarks in RPV SUSY
- Higgs boson
- W mass
- h→WW, double charged higgs
- Bs→μμ
- SUSY?

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Inclusive W cross section

- W→μν and W→eν signal:
- Backgrounds from QCD, Z→l+l−, W→τν and cosmic μ’s
- Excellent description by MC simulation

| Candidate events in 72pb-1 |  | Estimated
background | Acceptance x efficiency |
| --- | --- | --- | --- |
| W → μν | 31,722 | (10.6 ± 0.4)% | (17.94+0.36−0.33)% |
| W → eν | 37,574 | ( 4.4 ± 0.8)% | (14.39+0.32−0.31)% |

- σ(pp→W →lν ) = 2777 ±10(stat) ± 52 (syst) ±167 (lum) pb

- J. Stirling: SM (NNLO)=2770 pb

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Z Production Cross Section

- Z → e+ e− signal and  Z →μ+ μ− signals
- 66 < m(ll)/GeVc-2 < 116
- Small backgrounds from QCD, Z/W→τ, cosmics μ’s: less than 1.5%

| Number of events 
in 72pb-1 |  | acceptance x efficiency |
| --- | --- | --- |
| Z → e+ e−  | 4242 | (22.74 +0.47−0.48)% |
| Z → μ+ μ− | 1785 | (10.18+0.24−0.28)% |

- For 66<m(l+l-)<116 GeV/c2 :
- σ(pp→Z/γ* →l+l-) = 254.3 ±3.3(stat) ± 4.3 (syst) ±15.3 (lum) pb

- SM: 250.2 pb

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## W and Z Cross Sections: Summary

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Wγ Production

- pp → Wγ → lνγ:
- probes ewk boson self-coupling: direct consequence of SU(2)xU(1) gauge theory
- new physics, e.g. composite W modifies coupling
- Selection:
- 1 high-PT lepton (e,μ)
- 1 Photon with: ET>7GeV, ΔR(γ,l)>0.7
- 1 neutrino: large missing-ET>25 GeV

- Separate WWγ vertex from (boring)
- Lepton Bremsstrahlung

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Di-boson production: Wγ

- Di-boson production: Wγ

- NLO prediction (U. Baur):

- ET(γ)/GeV

- Next: extract WWγ coupling from
- Photon Et spectrum

|  | Nexp  (L=198.3/pb) |
| --- | --- |
| W+ MC  | 180.51+-2.08+-11.2 |
| W+jet BG | 49.52+-0.10+-14.95 |
| Z+ | 22.37+-0.38+-1.20 |
| W+ (tau) | 3.23+-0.24+-0.17 |
| Total SM  | 255.63+-2.13+-26.43 |
| data | 259 |

- Data agree with SM expectation:

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Zγ Production

-  pp → Zγ → l+l-γ
- 2 leptons with Et>25 GeV
-  1 photon with Et>7 GeV, 	ΔR(lγ)>0.7
- New physics at Zγ vertex?

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Di-boson production: Zγ

- Data agree with SM expectation:

- NLO prediction (U. Bahr)                               (LO + ET(γ) dependent k –factors):

|  | Combined e and μ |
| --- | --- |
| Z+ MC  | 65.76+-3.76  |
| Z+jet BG | 4.44+-1.33 |
| Fake Z | 0.26+-0.20 |
| Total SM  | 70.46+-4.00  |
| data | 69 |

- sigma*BR=5.3+-0.6(stat)+-0.3(sys)+-0.3(lumi) pb

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Run I: 
found 1 event with 2 photons, 2 electrons and large missing Et
SM expectation 10-6 (!!!)
Run II:
Any new such event would be exciting! 

- Run I:
- found 1 event with 2 photons, 2 electrons and large missing Et
- SM expectation 10-6 (!!!)
- Run II:
- Any new such event would be exciting!

**W/Z+gamma+X: more exclusive channels**

- SUSY?

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Search for +      

**                  **

** **_**Search Selection:**_** **
-      **2 central photons w/ Et>13(25)**
**     ****Cosmic/beam halo removal**

**   **_**For Missing Et>25GeV**_
**Expected background:   ****2********2**** **
**Observed: ****	****               ****2**

** ****Gravitino is the LSP**
** ****NLSP: Neutralino ********1******** ********G**
** ****Experimental Signature: ********+E****T**

****** ****Set cross section limit**_** **_

**SUSY would show up as an excess of events with large Missing Energy**

- Run 1: eeEt

- pp →XXY → GG + Y

**~ ~**

**~ ~**

- e.g.

**~ ~**

**~**

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## GMSB Search in +                        

**Set the lower mass limit on the lightest**
**chargino in GMSB:**_** **_
**           **_**M**__**c**__**>113 GeV @ 95% C.L.**_

**Acceptance**

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Di-lepton Production @ High Mass

- Select 2 opposite sign leptons: ee or μμ (ττ soon)
- Here ee channel:
- 2 central e (CC)
- 1 central and 1 forward e (CP)
- NEW: 2 forward e’s (PP)
- Good agreement with SM prediction

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Model Independent Limits: spin-0, spin-1 and spin-2 particles

- spin-0

- spin-2

- spin-1

-  model-independent limits on σxBR for particles with spins 0, 1 and 2
-  applicable to any new possible future theory
- Observed limit consistent with expectation
- New Plug-Plug result not yet included
- Muon analysis also ongoing

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Limits on Several Models

**Z’** occurs naturally in extensions of SM towards GUT scale, e.g. “E6” models
- M(Z’)>570 GeV for E6 models (depends on exact model: couplings to quarks and leptons)
- M(Z’)>750 GeV for SM coupling
- Sneutrino in R-Parity violating SUSY may decay to 2 leptons:
- M>600 GeV for couplingxBR=0.01
- Randall-Sundrum gravitons
- Mass> 600 GeV for k/MPl >0.01
- Techni- pion’s, -omega’s

- G

- ν

- Z’

**~**

- ν

**~**

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Z→e+e− Forward-Backward Asymmetry

- Tevatron uniquely sensitive to Z-γ* interference at high invariant masses.
- Shape of the Afb spectrum can be used to extract values for sin2(θW) and u, d couplings to Z
- Agreement with SM prediction.

- e+

- e−

- angle between
-  p and e−

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Lepton + Quark Resonances : Leptoquarks

- Apparent symmetry between the lepton & quark sectors: common origin ?

**e e**

-  LQs appear in many extensions of SM
-   (compositeness, technicolor...)
-  Connect  lepton & quark sectors
-  Scalar or Vector color triplet bosons
-  Carry both lepton and baryon number
-  fractional em. Charge: +-1/3, +-4/3, etc.
-  Braching ratio β unknown, convention:
- β=1 means 100% BR LQ→l±q
- β=0 means 100% BR LQ→νq
- Also sensitive to e.g. squarks in RPV  (exactly the same!)

- Nice competition between world’s accelerators:
- HERA, LEP and Tevatron
- At Tevatron: independent of coupling λ

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Leptoquarks: 1st  generation

- New analysis in run 2:
- Search for LQ’s decaying LQ→νq (β=1)
- 2 jets (Et>) and Et>60 GeV:
- Experimentally challenging
- Result:
- 124 events observed
- 118.3±14.5 events expected
-  exclude LQ masses with 78<M<118 GeV
- eejj channel:
- M(LQ)>230 GeV for β=1 (72 pb-1 )

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Leptoquarks: 2nd generation

- Signature:
- 2 high Pt muons
- 2 high Et jets
- Suppress Z→μμ background

- Expect 3.15±1.17 events, observe 2
-  Exclude LQ’s at M(LQ)<240 GeV

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Precision measurements of 
MW  =80.450 +- 0.034 GeV/c2
Mtop=174.3    +- 5.1     GeV/c2
Prediction of higgs boson mass within SM due to loop corrections, e.g. 

- Precision measurements of
- MW  =80.450 +- 0.034 GeV/c2
- Mtop=174.3    +- 5.1     GeV/c2
- Prediction of higgs boson mass within SM due to loop corrections, e.g.

- Indirect constraints versus direct searches! Will they agree?

- Mtop (GeV)

- MW (GeV)

- 193 GeV

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Towards W Mass

- Use MC templates to fit to signal + background
- CDF Run I                             mW = 80,465 ± 100(stat) ± 104(sys) MeV
- CDF Run II for 500/pb estimate:  =    X      ±  40(stat) ±   55(sys) MeV

- Difficult measurement  Work in progress – no results yet

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Towards Higgs: WW Production

- Motivation:
- Sensitive to WWγ and WWZ vertex
- Higgs discovery channel
- Anything new/unexpected?
- 2 leptons +missing Et +no jet with Et>15 GeV:
- Observed: 5 events
- Expected:
- WW:  6.89±1.53
- BG:    2.34±0.83

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Doubly Charged Higgs: H++/H--

- H++ (double charged higgs)  predicted in some extensions of SM and SUSY: M=100...1000 GeV
- Striking signature: decay into 2 like-sign leptons
- ee channel:
- M(ee)>100 GeV to suppress large BG from Z’s (conversions:    e±→e±γ→e±e+e- )
- eμ and μμ channels
- Sensitive to single and pair production of H++/H—
- Blind analysis
- search region: M>100 GeV
- 0 events observed
-      Result: 95% C.L. upper limit on
- cross section x BR for pair production (pp→H++ H--→l+ l+ l- l-)
- M(H++)>130 GeV

- background

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Rare Decays: Bs->μ+μ-

- Rare Decays: Bs->μ+μ-

- New Physics can enhance branching ratios of B-mesons:
- Measure BR in decay modes suppressed in SM
- E.g. Bs→μμ:
- Bs = bound state of b and s quark
- SM:     BR(Bs→μμ)~10-9
- SUSY: BR may be A LOT  higher (~tan6β ?)
- Blind analysis with a priori optimisation:
- 1 event observed, ~1+-0.3 expected
-     90% CL limits:
- BR(Bs→μμ)<5.8 X 10-7
- BR(Bd→μμ)<1.5 X 10-7

- SM vs e.g. SUSY

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## SUSY Sensitivity: Bs->μμ

- 90% CL limit: BR(Bs→μμ)<5.8 x 10-7

-  SO(10) GUT model (R. Dermisek et al.: hep/ph-0304101) :
- accounts for dark matter and massive neutrinos
- largely ruled out by new result
- mSugra at high tanβ (A. Dedes et al.: hep/ph-0108037):
- Just about scratching the corner of parameter space
- In direct competition with higgs and (g-2)μ

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago

## Conclusion and Outlook

- Physics at CDF is back:
- Have twice the Run I luminosity and excellent detector
- Electroweak Measurements in good agreement with Standard Model:
- W and Z cross section, Di-boson production
- W mass in progress
- Searches for New Physics have started:
- Expect new physics at the TeV scale (hierarchy problem)
- Z’, Large extra dimensions, Leptoquarks, SUSY, Higgs
- Cover broad range of possible signals
- no signals yet but constraining theoretical models
- And many results I could not cover...

- Many New Exciting Results coming soon!

- Beate Heinemann - University of Liverpool

- 03-05-2004 U. of Chicago