# Presentation: 058248

## Beyond the Standard Model Searches

- Beate Heinemann
*University of California, Berkeley and Lawrence Berkeley National Laboratory*
- EPS 2007, Manchester, July 2007

**?**

**Introduction**
**Model-independent Searches**
**Supersymmetry Searches**
**Beyond Supersymmetry**
**Conclusions **

## 49 Parallel Session Talks

- Very busy session with large attendence:
- 25 experimental talks
- 5 HERA
- 9 Tevatron
- 7 LHC (see talk by O. Buchmüller)
- 2 Belle/BaBar
- 1 NA48
- 24 theory talks (see talk by G. Giudice)
- Conveners: Volker Büscher, Jose Espinosa, Emanuelle Perez
- Focus on results since ICHEP’06
- Apologies for not being able to cover all the results!

- Many thanks to: H. Abramowicz, C. Diaconu, Y. Gerstein, J.-F. Grivaz, C. Hays

## The Standard Model and the Standard Questions We Have

**What is the ****origin of electroweak symmetry breaking****?**
**Is there a Higgs boson?**
**WHERE IS IT?**
**What is the ****Dark Matter****?**
**Is it produced at colliders? **
**Is Nature ****supersymmetric****?**
**Are there ****new dimensions of space****? **
**Is there anything maybe that ****nobody has thought**** of and no one has looked for and we missed it?**

**Hierarchy problem:**
**New physics should be at the TeV scale!**

## High Energy Colliders: Tevatron and HERA

- High Energy Colliders: Tevatron and HERA

**   ****HERA Run I+II**
** ∫ ****Ldt = 0.5 fb****-1 ****/exp**

**Tevatron Run II **
**∫ ****Ldt = 3 fb****-1 ****/exp**

## Model-independent Searches

## HERA “Isolated Leptons”

- Longstanding excess from HERA Run I e+p data    (∫Ldt~100 pb-1):
- Main SM contribution from W production
- Excess concentrated at high pTX and only present in H1
- ZEUS and H1 had quite different selection cuts

| e+p data | H1 | ZEUS |
| --- | --- | --- |
| PTX>0 | 19/14.4 | 36/32.5 |
| PTX>25 GeV | 11/3.4 | 7/5.7 |

*[talk by D. South] *

## HERA 2 “Isolated Leptons”

- Use full HERA 2 luminosity
- Just 3 weeks after end of HERA!
- H1 and ZEUS settled on a common set of cuts
- H1 still sees excess (~3) and ZEUS does not
- Consistency of experiments: 2
- Combined significance of excess 1.8

| e+p data | H1 | ZEUS | H1+ZEUS |
| --- | --- | --- | --- |
| PTX>25 GeV | 17/7.1±0.9 | 6/7.5 ±1.1 | 23/14.6±1.9 |

**Excess will remain unresolved**
- Unless other collider sees something...
- On the bright side there is now a nice sample of **87 W candidates in e****±****p data**

## Flavor Changing Neutral Currents

- Possible explanation:
- ep t+X  lvb+X
- Requires flavor-changing neutral current
- Optimized selection using likelihood discriminant
- Data seem not consistent with this hypothesis
- |tu|<0.14 at 95% CL

**H1**

*[talk by D. South] *

**e********j**

****j

**H1**

## FCNC: tZ+q

- Standard Model predicts:
- BR(tWb) > 99%
- BR(*t**qZ*) ≈ O(10-14)
- Select events with 2 leptons and 4 jets:
- With or without b-tag
- Use 2 estimator to assess kinematic consistency with top production
- Data consistent with background estimate
- Main background: Z+jets production
- Result:

*[talk by A. Harel] *

**√********2**

- FCNC signal

- SM background

- Data

## Generic Searches: H1 and CDF

- Compare data to SM in “all” event topologies, e.g.:
- ee,e...eb...
- Data in good agreement with Standard Model in overall event count
- H1 looked in 99 final states
- both e+p and e-p data
- CDF looked in 344 final states

*[talk by A. Schöning] *

- (Ndata-NSM)/ 

## CDF: Test of distributions

- Analyse ~16500 kinematic distributions using Kolmogorov-Smirnov test
- Some disagreements in kinematic distributions
- but appears to be due to QCD mismodeling and not due to new physics

- KS test 

## Global Search for Excess at high pT

- Global Search for Excess at high pT

**Evaluate most discrepant tail/region in ∑p****T**** distribution**
- H1 uses also inv. Mass of all objects
**Found no significant discrepancy**
- Excess in most discrepant distribution is not significant
**Only sensitive if** **new physics is large and at high ∑ p****T**:
- Useful for looking for the unexpected
- Typically less sensitive than dedicated analysis, e.g. at CDF
- WZ production:
- Would need O(10) times more data for 5 discovery
- Z ́ production
- Would need O(2) times more data for 5 discovery at ~250 GeV

- e±ET

**H1**

## Supersymmetry

## Supersymmetry (SUSY)

- SM particles have supersymmetric partners:
- Differ by 1/2 unit in spin
**Sfermions** (squarks, selectron, smuon, ...): spin 0
**Gauginos** (chargino, neutralino, gluino,...): spin 1/2
- SUSY can solve the fine-tuning problem

## Sparticle Spectrum

- Typical features:
-  Squarks and gluinos heavy
-  Sleptons light
-  5 Higgs bosons (in MSSM)
-  Charginos and neutralinos  light
-  Third generation partners lightest (, t, b,..)

## MSSM Higgs Boson Search

- Minimal Supersymmetric Standard Model:
- 2 Higgs-Fields: Parameter tan=<Hu>/<Hd>
- 5 Higgs bosons: h, H, A, H±
- Neutral Higgs Boson:
- Pseudoscalar A
- Scalar H, h
- Lightest Higgs (h) very similar to SM
- At high tanß:
- A is degenerate in mass with either h or H
- Decay into either  or bb for mA<300 GeV:
- BR(A ) ≈ 10%, BR(A bb) ≈ 90%
- Cross section enhanced with tan2

- C. Balazs, J.L.Diaz-Cruz, H.J.He, T.Tait and C.P. Yuan, PRD 59, 055016 (1999)
- M.Carena, S.Mrenna and C.Wagner, PRD 60, 075010 (1999)
- M.Carena, S.Mrenna and C.Wagner, PRD 62, 055008 (2000)

*[talk by P. Jonsson] *

## MSSM Higgs Boson Search

- Data mass distribution agrees with SM expectation mostly:
- CDF: Slight excess (~2)
- DØ: slight deficit in that region
- Sensitive to tan≈50

- Events/10 GeV

*[talk by P. Jonsson] *

## Lepton Flavor Violation

- Lepton flavor violation is clear signal of new physics
- e.g. sensitive to SUSY at high tan
- Belle/Babar:
- BR(,,...)
- BR()<10-54 in SM, up to 10-7 in BSM
**Experiments are now probing BR~10****-8**
- NA48/KLOE:
- RK=(K)/ (Ke)
- Enhanced by tan6/mH±4
**Current precision ~2-3%**
- Goal 0.3%
- Also (K)/ ()

- Strong constraints on new physics and nicely
- complementary with direct searches

*[talks by T. Spadaro, R. Fantechi, Y. Miyazaki, F. Wilson] *

- Bs, B :
- A.Savoy-Navarro,
- J.Haba

## Squarks and Gluinos

- Squark and Gluino production:
- Signature: jets and
- At Tevatron no long cascades to leptons expected:
- Lepton veto applied
- Analysis optimized depending on mass hierarchy

- ET

*[talk by X. Portell] *

- QCD
- jet BG

## Supersymmetry Parameter Space

- M(g)>290-410 GeV, M(q)>375 GeV

- ~

- ~

- NB: up to 10 GeV differences depending on treatment of theoretical cross section uncertainties

## Exclusion of GUT scale parameters

- Nice interplay of hadron colliders and e+e- colliders:
- Similar sensitivity to same high level theory parameters via very different analyses
- Tevatron is starting to probe beyond LEP in mSUGRA type models

- LEP excl.
- (chargino)

- LEP excl.
- (slepton)

- DØ excl.
- (squark/gluino)

**mSUGRA**

## The lightest q’s:
Due to large SM top mass
Dedicated searches for stop and sbottom:
t c01 and bb01
Signature:
Two heavy flavor jets + large missing ET

- The lightest q’s:
- Due to large SM top mass
- Dedicated searches for stop and sbottom:
- t c01 and bb01
- Signature:
- Two heavy flavor jets + large missing ET

- Third Generation Squarks

- ~

*[talk by C. Biscarat] *

- mh (GeV)

- mstop (GeV)

- ~

- ~

- ~

- ~

- HT=∑PTjet

- max+ min

## Stop and Sbottom Mass Exclusion

- Stop masses excluded up to 150 GeV/c2
- If m(t)-m(01)>60 GeV/c2
- Sbottom masses excluded up to 220 GeV/c2
- If m(01)<80 GeV/c2

- ~

- ~

- ~

## Charginos and Neutralinos 

- Charginos and Neutralinos:
- Mixed states of SUSY partners of
- W, Z,  , Higgs
- Typically among the lightest SUSY particles
- Challenges:
- Maximize lepton acceptance!
- Large fraction of events contain ’s
- Selection:
- Isolated leptons:
- 3 leptons (e, or “track”)
- 2 leptons of same electric charge
- Missing ET

- ~

## Trileptons: Result

| Analysis | Expected
background | Data |
| --- | --- | --- |
| ll | 1.30.3 | 1 |
| ell | 0.80.4 | 0 |
| ee + track | 1.00.3 | 3 |
| l | 0.40.1 | 1 |
| e±e± | 3.00.5 | 4 |
| e±± | 4.00.6 | 8 |
| ±± | 0.90.1 | 1 |

| e+track | 0.9+0.4-0.1 | 0 |
| --- | --- | --- |
| ee+track | 0.8  0.7 | 0 |
| +track | 0.3+0.7-0.1 | 2 |
| ±± | 1.1  0.4 | 1 |

- Main backgrounds:
- Instrumental: Z+, Z+jet
- Genuine: WZ/*

- CDF

*[talk by H. Fox] *

- DØ

## Constraints on SUSY

**Strongly model-dependent limits:**
- No-mix scenario:
**CDF m(********±****1****)>129 GeV/c****2****, DØ: m(********±****1****)>140 GeV/c****2**
- Starting to probe mSUGRA
- No sensitivity at large m0 yet (i.e. if sleptons heavy)
**Sensitive up to m(********±****1****)~200 GeV with full Run 2 luminosity**

- CDF limit

- ~

- ~

- ~

## Gauge Mediated SUSY Breaking

- Lightest SUSY particle is gravitino:
- Mass ~ 1 keV
- Next-to-lightest particle is
- neutralino G
- Reaction: pp XX GG
- Cleanest signature:
- 2 photons+missing ET

|  | ET>30 | ET>60 |
| --- | --- | --- |
| BG | 9.8 ± 1.1 | 1.5±0.4 |
| Data | 16 | 4 |

| ET>30 | ET>50 |
| --- | --- |
| 19.5 ±2.5 | 1.6 ± 0.3 |
| 22 | 4 |

**CDF**

**DØ**

**Missing E****T ****/GeV**

** ****Slight excess in both experiments**
** ****DØ Data exclude chargino masses below 231 GeV**

- [talk by S.-S. Yu]

- _

- ~

- ~

## Long-lived particles

- Particles can be stable or long-lived if decay forbidden due to
- Conservation law
- Kinematically disfavored
- Example Models:
- Split-SUSY:
- gluino
- GMSB, AMSB:
- stau, stop, chargino
- In the detector
- Decay after some lifetime
- Get stuck in detector and decay later
- Escape detector completely

*[talk by M. Goncharov] *

## CHAMPS: Charged Massive Stable Particles

- CHAMPS: Charged Massive Stable Particles

- Scenario:
- Escape detector completely
- Experimentally:
- Search for “muons” that travel at <<1
- CDF: Time-Of-Flight detector and drift chamber
- D0: muon system
- Reconstruct mass from p and 
- Cross Section Limits
- (for pT>40 GeV and ||<1, 0.4<<0.9)
- Weakly interacting (, 1±):
- <10 fb at 95% CL
- Strongly interacting (stop):
-  <48 fb at 95% CL
- Assumes stop stays charged up to muon system with P=43±7%

**CDF: m(t)>250 GeV**
**DØ:   m(********1****±****)>140-170 GeV**

- ~

- ~

- ~

- ~

## Particles can be rather stable:
Lifetime ~hours
Interact in calorimeter and decay at some later time
Split-SUSY: 
m(q)>102 TeV, m(g)~TeV
Gluino long-lived
Trigger on events with 
“no interaction” but jet activity
Main background:
Cosmic ray and beam-halo muons
Result: m(g)>270 GeV @95%CL

     for (g)<3h, (RmRb)=3mb, BR(gg10)=100%, m(10)=50 GeV

- Lifetime ~hours
- Interact in calorimeter and decay at some later time
- Split-SUSY:
- m(q)>102 TeV, m(g)~TeV
- Gluino long-lived
- Trigger on events with
- “no interaction” but jet activity
- Main background:
- Cosmic ray and beam-halo muons
- Result:** m(g)>270 GeV **@95%CL
-      for (g)<3h, (RmRb)=3mb, BR(gg10)=100%, m(10)=50 GeV

- Stable particles: “stopped Gluinos”

**~**

- ~

- ~

- ~

*[A. Arvanitaki et al.: **hep-ph/0506242**] *

- ~

- ~

- ~

## Beyond SUSY

## What else could be there?

- Strong theoretical desire for SUSY to be true
- particularly due to the **lack of SUSY observation...**
- There could be many other theories/particles, e.g.:
- Extra gauge groups: **Z’, W’**
- Occur naturally in GUT scale theories
**Extra spatial dimensions: **
- “Solve” hierarchy problem by making gravity strong at TeV scale
**Compositeness: **
- excited leptons, leptoquarks
**Preons:**
- We have always found smaller things before
- atom->proton->quarks->preons ?
**...**

## High Mass Production

- Probes contact interactions:
**  **
- Probes new resonances: Z’, W’, Extra Dimensions
- Probes fermion substructure

- =

## High Mass Production

- Inclusive cross sections:
- HERA: d/dQ2 (CC and NC)
- Tevatron: d/dM(l+l-,jj,)
- Excellent agreement with prediction over many orders of magnitude

- ppjj+X

## Contact Interactions + Quark Substructure

|  | constructive |  | destructive |  |
| --- | --- | --- | --- | --- |
|  | ZEUS | DØ | ZEUS | DØ |
| LL | 4.2 | 3.6 | 4.2 | 6.2 |
| RL | 3.6 | 4.3 | 2.3 | 5.0 |
| VV | 6.3 | 4.9 | 7.5 | 9.1 |

- Rq<0.67 10-18 m

- Contact Interaction: eeqq
-  Constraints in TeV

- Quark Radius (ZEUS)

- No indication of substructure
- or contact interactions

*[talk by R. Placakyte] *

## Excited Leptons

- Excited leptons appear in compositeness models
- Decay modes:
- f*f’, f*f’W, f*f’Z
- Search for peak in invariant mass spectra:
- E.g. e*  e, e*eZ, *eW etc.

*[talk by E. Sauvan] *

** ****m(e********) [GeV]**

- H1: e*  e

- DØ: e*  e

- H1: *eW

## Excited Leptons

**Gauge Model**:

**Contact Interaction Model:**

- e*e

## ee and  Mass Spectra

- ee and  Mass Spectra

- Dielectron mass spectrum and diphoton mass distributions
- Data agree well with Standard Model spectrum
- No evidence for mass peak or deviation in tail

**ee**

****

*[talk by S. Kermiche] *

##     High Mass e+e- and 

- Resonance in diphoton or dielectron mass spectrum predicted in
- Z’ models (ee only): Spin 1
- Randall-Sundrum graviton (ee and ): Spin 2

**M****G ****> 890 GeV for k/M****Pl****=0.1**

**M****Z’****>925 GeV for SM-like Z’**

- ~

## High Mass  t t  Production

**Recent interest in KKG ******** tt**
- Good discovery potential at LHC
- Agashe et al.: hep-ph/061215
- Lillie, Randall, Wang: hep-ph/0701166
- CDF analysis
**Excludes M<720 GeV in topcolor models**
- Reinterpretation in KKG models ongoing

- LHC

- hep-ph/061215

- _

**_**

## W ́ e e

- W ́ boson searched for in tail of transverse mass distribution
- New DØ limit: **m(W ́) > 965 GeV at 95% CL**

- Transverse Mass (GeV)

## W ́tb

- Complementary:
- W ́e probes lefthanded current
- W ́tb probes left- and righthanded current
- Use Invariant mass of
- W(l)+2 jets (≥1 b-tag)
- Selection as in CDF single top analysis (see T. Wyatt’s talk)
- Mass limit
**M(W ́)>760 GeV for g ́=g****SM**

## Conclusions

**Huge efforts for finding physics beyond the Standard Model continue**
- Tevatron presented many analyses with 1 fb-1
- Another 2 fb-1 are on tape and a total of 8 fb-1 is expected by 2009
- HERA presented first results using their full luminosity
- Interesting interplay with low-energy experiments
- BaBar, Belle, KLOE, NA48..
**No signs of new physics found**
- Stronger and stronger constraints on new physics
- No excesses larger than 2

**Current experiments continue to improve **
**sensitivity and LHC is starting next year...**

## It has been a rainy decade for searches

- Let’s hope the next decade is sunnier...starting with EPS 2009

## Backup Slides

## BsBranching Ratio

- Standard Model prediction:
- BR=(3.42±0.54) x 10-9
- A.J. Buras Phys.Lett.B 566, 115 (2003)
- Large enhancements e.g. in Supersymmetry possible

|  | CDF 
L=0.8 fb-1 | DØ 
L=2.0 fb-1 |
| --- | --- | --- |
| Nexp | 1.47 | 2.3 |
| Nobs | 0 | 3 |
| Limit at 95%CL | <10 x 10-8 | <9.3 x 10-8 |

- BR(Bs)
- excluded

- Severe constraints on SUSY parameter space

- ~ tan6/mA4

## Multi-Leptons at HERA

- Inclusive searches for
- 2 or 3 leptons
- Sensitive to H±± production
- Good agreement with SM
- Also in e,, e
- Limits derived on H±± production

|  | H1 : e±p
459 pb-1 | ZEUS: e±p
432 pb-1 |
| --- | --- | --- |
| ee | 3
1.5±0.3 | 5
4.3±1.1 |
| eee | 3
0.9±0.2 | 1
1.1+0.5-0.1 |

**ZEUS**
**(prel.)**

## CDF Photon Events

- CDF Run 1: L~100 pb-1
- One spectacular event:
- eeET
- SM expectation 10-6
- Inspired GMSB SUSY models:
- Selectron pair production?
- Excess in ET events
- NData=16
- NSM= 7.6+-0.7
- Could also be explained in GMSB with R-parity violation
- Resonant smuon production?
- Now follow up with 10 times more data

*[S. Ambriosano et al.]*

*[B. Allanach et al.]*

- CDF Run 1: ET

## Follow up on Run1 CDF events

- Lepton+photon+ET analysis
- Designed to use same cuts as Run 1
- NData=67
- NSM  =55.7±7.1
- eeET:
- No event observed

- CDF Run 2 prel.: ******E****T**

- ∫ Ldt=0.93 fb-1

- Run 1 excesses not confirmed by Run 2 data

*[talk by S.-S. Yu.]*

## Search in +MET Channel

- Highest MET event:
- MET=165.1 GeV
- Pho1 ET=304.6 GeV (largest pho ET)
- Pho2 ET=20.3 GeV
- Jet ET=143.6 GeV
- HT=633.6 GeV (2nd largest HT)
- Nvx=1, zvx=-25.6 cm

- Run 199148, Event 1171816