# Presentation: 293997

## Search for New Phenomena at Colliders

- E. Nagy (CPPM)
- for the
- CDF, D0 (Tevatron)
- and
- H1, ZEUS (HERA)
- Collaborations

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## In spite of the great success of the SM we still miss an ultimate theory (TOE) which would provide unification of all the 4 known forces (gravity!) into a finite (renormalizable) theory.

- Therefore, new, BSM physics is expected at some energy scale MX.
- The questions are: what is the TOE and what is MX?
- Today only elements of such a theory are proposed for experimental tests. In the present talk: some arbitrary choice of topics addressed by two active colliders: Tevatron and HERA.

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Extra Dimensions
Super Symmetry
Z’, Lepto-Quarks, Beyond SM Higgses
Substructure (Contact Interactions, Excited Leptons)
Anomalies

- Super Symmetry
- Z’, Lepto-Quarks, Beyond SM Higgses
- Substructure (Contact Interactions, Excited Leptons)
- Anomalies

- Frequently, the same event topology (e.g. high mass di-leptons) allows to test several theoretical models

- For MX  the natural value is MPl to unify gravity.
- However this leads to « unnatural » fine tuning of scalar masses (problem of hierarchy).
- Some of the above topics present solution to this problem.

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Tevatron

- ~ 200 pb-1 and only most recent results from Run II reported here

- >3 times more luminosity than in Run I;
- soon **L** is 1032cm-2s-1 and counted in  fb-1

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## HERA

- Results mainly from HERA I

- HERA I Luminosity

- HERA II will deliver ~10 times more luminosity (at present ~70 pb-1)
-  + longitudinal polarisation of e-beam

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Extra Dimensions (ED)

-  ED’s provide framework for unification with gravity (Th. Klauza, 1919)
-  ED’s are compact since not seen (O. Klein, 1926)
-  Compact ED’s generate replica of particles (KK-tower) propagating in them
-  In string theories, ED’s restore QM probabilities in the range [0,1].
-  ED’s can be large (LED: R>>TeV-1) – if only gravity can propagate in them
-  LED can explain why gravity is weak: 1/G~M2Pl~Msn+2 Rn  and can solve the hierarchy problem: Ms~MW
-  LED can be tested by gravity experiments (n<3) but also at colliders through virtual effects or direct emission of KK gravitons (n>2).
-  Smaller ED’s (R~ TeV-1) can also be tested at colliders (interference of KK states)
-  Randall-Sundrum model (1 small ED of size R~1/MGUT with a metric damped by e-kRφ ) predicts graviton resonances (S=2) of k~1.

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Determination of Ms of LED 

- Look for effects of virtual gravitons in high mass lepton (photon) pairs

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Select: 

- Select:
- 2 (and only 2) high pT em objects: pT>25 GeV
- Precisely determined vertex
- Compare:
- SM and instrumental (mis-ID) background
- Extract limit:

|  | η(TeV-4) | MS(TeV) |
| --- | --- | --- |
|   λ= +1 | 0.292 | 1.22 |
|   λ = -1 | -0.432 | 1.10 |

- E.Nagy: Searches for  New Phenomena at Colliders

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## CDF ee limit

|  | η(TeV-4) | MS(TeV) |
| --- | --- | --- |
|   λ= +1 | 1.17 | 0.961 |
|   λ = -1 | 1.05 | 0.987 |

- Limit on MS from HERA
- η=λ/MS4

|  | H1 | ZEUS |
| --- | --- | --- |
| λ= +1 | 0.82 | 0.78 |
| λ = -1 | 0.78 | 0.79 |

- E.Nagy: Searches for  New Phenomena at Colliders

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## Determination of Md from KK graviton emisson

- Signature is Monojet + MET

- Selection:
- Leading jet pT>150 GeV
- 2nd jet pT < 50 GeV
- MET>150 GeV
- Lepton (e,μ) veto

- Main Background:
- Z(->νν)+nj
- W(->lν)+nj

- Main uncertainty:
- Jet energy scale

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Determination of MC of TeV-1-size (Longitudinal) ED

- Fermions are confined in the ordinary 3d world.
- Gauge bosons can propagate in 3+δ brane of δ compact ED.
- Look for effects of KK replica of gauge bosons in high mass lepton pairs and determine the scale  MC of ED.

-  Same selection as above + trackmatch of at least 1 em object
-  Data is compatible with SM
-  Mc > 1.12 TeV @ 95%

- Interference of KK states

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Search for Randall-Sundrum resonancesin high mass di-lepton states

- E.Nagy: Searches for  New Phenomena at Colliders

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## SUper SYmmetry

- Symmetry of Nature for  Boson<->Fermion interchange
-    Basic ingredient for unification with gravity (SuperString/M-theory)
-    The only nontrivial extension of the Lorentz-Poincaré group
-    Provides elegant solution for the hierarchy problem
- Minimal extension of the SM: MSSM
-    every SM particle has ΔS = 1/2 partner
-     R = (-1)3B+2L+S = +1 (SM); = -1 (SUSY)
-     2nd Higgs doublet is needed

- If SUSY were exact: only 1 additional parameter (μ) needed

- E.Nagy: Searches for  New Phenomena at Colliders

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##   many more parameters describe breaking

**  **many more parameters describe breaking
-    with additional hypotheses they are reduced in the 2 models treated here
-    gravitation mediated (mSUGRA) model to 5 (m0, m1/2, tanβ, sgnμ, A0)
-     gauge mediated (GMSB) model to 6 (Λ, Mm, N5, tanβ, sgnμ, Cgrav) parameters.
- R-parity is approximately conserved:
**  **severe limits on B- and L-violating processes
-    SUSY partners are pair produced
-    LSP is stable (neutral and weakly interacting)
- Basic signature is MET (LSP), + multiple jets and leptons** **
**   **from cascade decays
- Main bg is t tb and gauge boson pair production
- Small violation of R-parity is not excluded:
**  **allows single resonant formation of SUSY particles
-    many more jets/leptons in final state
-    additional  couplings (48)
- At Tevatron both RPC and RPV can be studied
- HERA is competitive only for RPV processes

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## The “golden” signature: chargino (χ1±) and neutralino (χ20) pair production

- The signatures exploited by D0:
- MET from χ10 and ν +
- 3 leptons (e,μ,l/e,e,l) or
- 2 leptons (μ, μ) of same sign

- D0 has searched beyond the stringent mSUGRA LEP limit
- and has chosen the following parameter region:

- E.Nagy: Searches for  New Phenomena at Colliders

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## e+ μ +l  

- High quality, isolated
- electron: pT>12 GeV
- muon: pT>8 GeV
- charged track

- Jet veto
- mTe >15 GeV
- mee<60 GeV
- Δφee<2.8
- MET>20 GeV
- pT3xMET> 250 GeV2
- 1 data – 0.27±0.42 bg

- e+e+l

- High quality, isolated
- electrons:
- pT>8,12 GeV

- Jet veto
- mTmin >15 GeV
- 15<meμ<100 GeV
- METsignif>25 GeV1⁄2
- pT3> 3 GeV
- 0 data – 0.54±0.25 bg

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## μ± μ±   

- High quality, isolated
- like-sign muons:
- pT1>11 GeV, pT2>5 GeV
- MET>15 GeV
- mμμ<80 GeV
- Δφμμ<2.7 (if pT2<11 GeV)
- ΔφMETμmin>0.5 (if pT2<11 GeV)
- ΔφMETμmax<2.4 (if pT2<11 GeV)
- ΔφMET,j<2.4
- 1 data – 0.13±0.06 bg

- Bg is mainly heavy flavour
- Estimated from OS pairs

- Combined 3l+MET

- Great improvement wrt Run I
- Sensitivity very near to  mSUGRA prediction

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## mSUGRA

- At least 2 jets:
- pT1>60 GeV
- lepton veto
- ΔφMETjmin>30o
- ΔφMETjmax<165o
- MET>175 GeV
- HT=ΣpTj>275 GeV
- 4 data – 2.67±0.95 bg
- Bg mainly Z->vv+nj

- E.Nagy: Searches for  New Phenomena at Colliders

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## GMSB 

- Select 2 photons pT > 20 GeV

- Expected signal
- vs M=2Λ messenger mass scale

- Best limit on: Λ > 78.8 TeV
- mχ0 > 105 GeV, mχ± > 192 GeV

- Signal is at high MET:
- MET > 40 GeV
- Data: 1 Bg: 2.5±0.5

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## R-parity violation

- Introduces 48 new L and B violating Yukawa couplings:

- with more leptons, jets in the final state

- Single sparticle production and decay
- depends on coupling λ

- Decay of the LSP (χ10) – if fast,
- does not depend on coupling λ

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Look for signal in multiple event topology (H1). Below an exemple of the lepton-jet(s) inv mass spectrum No deviation from the SM -> Limits on λ1j1 and m0, msq, tanβ 

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## R-parity violation in GMSB (H1)

- Signature: MET>25 GeV, and an isolated γ (pT>25 GeV)
- 1 event found, 2.55±1.30 expected
- Limits on λ’1j1, mNLSP, msel

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## CDF: agreement of the high mass di-lepton spectra with the SM is transformed into limits on λ’ and msnu 

- E.Nagy: Searches for  New Phenomena at Colliders

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## Z’

- E6 and little Higgs models are considered here

|   θ | 0o | 90o | 37.76o | -37.76o |
| --- | --- | --- | --- | --- |
|  Z’ | Zψ | Zχ |     Zη |     ZI |

- E.Nagy: Searches for  New Phenomena at Colliders

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## Limits for e+e- (in GeV)

-          SM Couplings
- 	CDF :               750
- 	DØ:                  780
- 	E6	    ZI    Zχ     Zψ   Zη
-       CDF:      570  610   625  650
-       DØ:        575  640   650  680

- Limits for e+e- (in GeV)

- Similar, somewhat smaller limits for μ+μ-

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Little Higgs 

- Proposes new fermions and bosons to solve the hierarchy problem.
- Contrary to SUSY, here the quadratically divergent diagrams are cancelled by the same type of particle (fermion-loops by  fermion-loops, etc.)
- ZH is one of the new bosons to cancel divergent boson loop.
- Its coupling is parametrized by Θ.
- CDF establishes limits on the mass of ZH and Θ in both of ee and μμ final states.

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Lepto-Quarks

- Hypothetical bosons (scalars or vectors) carrying both L and B.
- Proposed in several extension of SM based on Q-L symmetry.
- HERA is an ideal machine to produce 1st generation LQ’s.
- No deviation is found wrt SM -> Limits on MLQ and coupling λ

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## ZEUS has also searched for tau’s in the final state:  Lepton Flavour Violation 

- No events have been found:
- limits on λeq1 = λτqj vs MLQ

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## 1st generation Lepto-Quarks at Tevatron

- Dominantly produced in pairs of the same generation (avoid topology of FCNC or LFV)
- Production is ~independent of λ
- Final state is characterized by 2j+2l
- lepton can be charged or neutral with BR β
- -> possible final states: 2j+2l, 2j+l+MET, 2j+MET

- 2j+2e channel:
- 2j ET>20 GeV
- 2e ET>25 GeV
- Z-veto
- ST=ΣETj+ΣEte>450GeV
- 0 data, 0.4±0.1 bg

- 2j+ev channel:
- 2j ET>25 GeV
- 1e ET>25 GeV
- MET>30 GeV
- W-veto: mT>130 GeV
- ST>330GeV
- 2 data, 4.7±0.9 bg

|     β | 0.1 | 0.5 | 1.0 |
| --- | --- | --- | --- |
| Run I | 110 | 204 | 225 |
| Run II | 155 | 213 | 238 |

- D0 MLQ1 limits in GeV

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Similar analyses of CDF - also in the jjMET channel

- MET+Jets channel:
- >2j (j1,2 central w/4 tracks)
- Jets and MET shouldn’t be aligned
- e/μ-veto
- MET>60 GeV
- 80<ΔΦ(j1,j2)<165o
- 124 data, 118±13 bg
- 78<MLQ<117 GeV excluded

- CDF MLQ1 limits in GeV

|     β | 0.1 | 0.5 | 1.0 |
| --- | --- | --- | --- |
| Run I |  | 182 | 220 |
| Run II | 135 | 197 | 230 |

- E.Nagy: Searches for  New Phenomena at Colliders

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## 2nd generation Lepto-Quarks at Tevatron

- 2nd generation Lepto-Quarks at Tevatron

- jj+μμ channel:
- 2μ pT>25 GeV
- 2j ET1,2>30, 15 GeV
- Z-veto
- Topological cuts (see Fig.)
- 2 data, 3.2±1.2 bg
- MLQ<240 GeV excluded

- MLQ<186 GeV excluded (L=104 pb-1)

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Beyond SM Higgses

- H->γγ
- H->WW
- Neutral SUSY/2-Doublets: h,H,A
- H++/--

- On the way to discover HSM ...
- ... one may find BSM Higgses

- E.Nagy: Searches for  New Phenomena at Colliders

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## In some extensions of the SM BR(H->γγ) can be ~ 1
(e.g. Fermiophobic or Topcolor Higgs)

- (e.g. Fermiophobic or Topcolor Higgs)

- Select 2 isolated photons:
- pT1,2>25 GeV
- pTγγ>35 GeV
- Estimate background:
- Instrumental, DY, γγ
- Determine limit on BR:
- sliding window technique

- E.Nagy: Searches for  New Phenomena at Colliders

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## H->WW->2l+MET

- H->WW->2l+MET

- ee (OS) channel:
- pT1,2>12,8 GeV
- MET>20 GeV
- METsig>15 GeV1/2
- Σ:pT+MET>100 GeV
- 12< Mee < 80 GeV
- Jet-veto
- Δφee<1.5
- 2 data, 2.7±0.4 bg

- eμ (OS) channel:
- pTe,μ>12,8 GeV
- MET>20 GeV
- METsig>15 GeV1/2
- Σ:pT+MET>90 GeV
- MTmin < 20 GeV
- Jet-veto
- Δφeμ<2.0
- 2 data, 3.1±0.3 bg

- μμ (OS) channel:
- pT1,2>20,10 GeV
- MET>30 GeV
- MET>10+0.75×pT1 GeV
- Jet-veto
- Z-veto
- Δφμμ<2.0
- 2 data, 3.1±0.3 bg

- E.Nagy: Searches for  New Phenomena at Colliders

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##  H,h,A (φ)

- Select:
- >2j ET1>20 GeV, ET2,3> 15 GeV
- with well defined vertex (>3 tracks)
- Apply b-tag with SVT algorithm
- εtag=0.75, εbtag=0.51, εctag= 1/4εbtag, fake=0.02

- Background:
- Multijet fakes (estimated from data)
- HF + fakes (estimated from data and MC)
- Bg is normalized to data outside the signal
- Limits for mA=mh(<135) or mA=mH(>135GeV)
- and for tanβ are calculated

- σφ~tan2β

- E.Nagy: Searches for  New Phenomena at Colliders

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## H++/--

**TEVATRON**

- Predicted in L-R symmetric, Triple Higgs, Little Higgs, etc. models

- Signature is multilepton (SS) events

- At HERA one searched for multi-e events (in general):
- H1 finds 6 multi-e events with M12>100 GeV (0.54±0.6 expected)
- No excess for ZEUS: 2 found (1.2±0.1 expected)

- However only 1 event of H1
- agrees with H++/-- topolgy
- Limit on coupling hee vs MH

- E.Nagy: Searches for  New Phenomena at Colliders

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## D0 selected events in the 2μ channel:

- D0 selected events in the 2μ channel:
- At least 2 isolated muons, pT>15 GeV of same charge with  ΔΦ<0.8 (anti-Z)
- Bg mainly HF and Z (wrong charge id)
- 3 events observed, 1.5±0.4 expected

- CDF selected events in the ee, eμ and μμ channels

- 0 events observed

- Predicted background

| Channel | Events |
| --- | --- |
|    ee | 1.8+0.8-0.6 |
|    μμ | 0.8+0.6-0.5 |
|    eμ | 0.9+0.4-0.4 |

| Mass Limit | CDF 
240 pb-1 |  | D0 
113 pb-1 |  |
| --- | --- | --- | --- | --- |
|  | HL++ | HR++ | HL++ | HR++ |
| ee | 135 | ~102-113 |  |  |
| μμ | 135 | 113 | 118.4 | 98.2 |
| eμ | 115 |  |  |  |

- E.Nagy: Searches for  New Phenomena at Colliders

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## Substructure of quarks and leptons

- A possible substructure manifests itself by:
-  Excited states of quarks and leptons
-  Finite size of quarks and leptons
-  Contact interaction of q’s / l’s of scale Λ>>sqrt(s)

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Excited Leptons at the Tevatron (CDF)

- Contact interaction

- Gauge mediated interaction

- Select eeγ events:
- ETe1,ETe2,ETγ>25 GeV
- Z-veto
- 3 events observed

- Expected background events:

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Excited Leptons at the Tevatron (CDF)

**Λ**** - **compositness scale
- f – relative coupling
-     strength to SU2L
-     gauge boson

- E.Nagy: Searches for  New Phenomena at Colliders

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## Contact Interactions

- Deviation from the SM of inclusive ep->eX is parametrized as:

- No deviation (ZEUS, H1) is transformed to limits on Λ:

- and also to limits on q-radius:
- Rq<1.0 10-18 m (H1)
- Rq<0.85 10-18 m (ZEUS)

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

##  General search for deviations from the SMpioneered by D0, here carried out by H1

- HERA I

- HERA II

- Select events with at least 2 isolated objects: e, μ, j , γ,  ν with PT > 20 GeV
- to look for large deviation from SM in Mall and ∑pT

- Largest deviation
- in μ-j-ν

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

##  Excess of isolated leptons at HERA

- 5 H1 events are compatible with FCNC single top production:
- σ(ep->etX) = 0.29±0.15 pb
- Alternatively, upper limit on:
- ktuγ <0.27 @ 95%CL
- ZEUS is compatible with SM:
- limit on vtuZ vs ktuγ

- Is the tau excess of ZEUS a sign of stop decay
- at large tanβ?

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Conclusions

- The performances of both Tevatron and HERA improve steadily
- allowing to test experimentally many new ideas in the search for an ultimate theory
- Although some anomalies observed already,
- no conclusive sign of new, BSM physics yet

- More results are expected soon...

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## Acknowledgments for help in preparing this materialto colleagues of the D0, CDF, H1 and ZEUS collaborationsand especially to Elisabetta Gallo (ZEUS) andJianming Qian (D0) 

- Apologies for subjects I haven’t had time to present here

- E.Nagy: Searches for  New Phenomena at Colliders

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## Backup slides

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## The CDF upgraded detector

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## The D0 upgraded detector

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## The H1 detector

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004

## The ZEUS detector

- E.Nagy: Searches for  New Phenomena at Colliders

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## Extra Dimensions

- E.Nagy: Searches for  New Phenomena at Colliders

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## Highest DiEm Masses

- Mee = 475 GeV
- cosΘ*=0.01

- Mγγ = 435 GeV
- cosΘ*=0.02

- E.Nagy: Searches for  New Phenomena at Colliders

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## Analogous study for stop (H1) assuming mst>msbDoesn’t explain isolated lepton events -> Limits on λ131 and mst

- E.Nagy: Searches for  New Phenomena at Colliders

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## Z’->μμ

- E.Nagy: Searches for  New Phenomena at Colliders

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## Excited Leptons

- E.Nagy: Searches for  New Phenomena at Colliders

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## Excited Leptons at the Tevatron (CDF)

- E.Nagy: Searches for  New Phenomena at Colliders

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##  Multi-e events at HERA II

- E.Nagy: Searches for  New Phenomena at Colliders

- PIC Boston, June 2004