Search for SUSY and Extra Dimensions at LEPklein/ichep.pdf · Search for SUSY and Extra Dimensions at LEP. Outline Four abstracts submitted: Supersymmetry f Searches for gaugemediated

Katja Klein (OPAL)1. Physikalisches Institut B, RWTH Aachen

On behalf of the LEP collaborations

July 29th, 2006 ICHEP 2006, Moscow

Search for SUSY and Extra Dimensions at LEP

OutlineFour abstracts submitted:Supersymmetryf

● Searches for gaugemediated Supersymmetry breaking topologies in e+e collisions at LEP2 (OPAL; Eur. Phys. J. C46 (2006) 307341)

Extra dimensionsf

● Single and multiphoton events with missing energy in e+e collisions at LEP (L3; Phys. Lett. B587 (2004) 1632)g

● Search for one large extra dimension with the DELPHI detector at LEP2 (DELPHI; 2006002 CONF 748, June 22nd, 2006)g

● Search for branons at LEP (L3; Phys. Lett. B597 (2004) 145154)f

All li

mits are

at 95% C.L. !

Katja Klein Search for SUSY and Extra Dimensions at LEP 3/22

GMSB: Motivation● No SUSY particles discovered yet Supersymmetry (SUSY) is a broken symmetry● Two most popular mechanisms for spontaneous SUSY breaking: Gravity Mediated (SUGRA) and Gauge Mediated SUSY Breaking (GMSB)

100 TeV < √F < 2000 TeV


E

M

√F

Hidden sector;breaks SUSY

Messenger

Visible sector:SM and SUSY particles

Mass scale

SUGRA GMSB

gravitational interaction

gauge interactions

MP

SUSY breaking scale √F 1011GeV

MP


G heavy G light


sectorMass scale M

M G ~ F /M P


● 6 parameters in minimal GMSB model:

M messenger mass scaleN number of generations of messenger particles √F SUSY breaking scale SUSY particles mass scaletan ratio of VEVs of Higgs doubletssign sign of Higgs sector mixing parameter

● ~ eV – GeV gravitino is the Lightest SUSY Particle (LSP)● Three possibilities for the Nextto LSP (NLSP) and its decay:

stau NLSP scenario: slepton coNLSP scenario: neutralino NLSP scenario:

LNLSP ~ 100 GeV

mNLSP

5

F /k100 TeV

4 E NLSP

2

mNLSP2 −1 ×10−2 cm

10 G

1 Gl l G ; l= eR , R , 1

NLSP lifetime is arbitrary:

Dimopoulos, Thomas, Wells,Nucl. Phys. B488 (1997) 39;g

Guidice, Rattazzi, Phys. Rept. 322 (1999) 419;g

Ambrosanio, Kribs, Martin, Phys. Rev. D56 (1997) 1761

(k = model dep. parameter of SUSY breaking)

GMSB: Motivation

M G


GMSB (OPAL): Slepton NLSP Topologies

Topology in detector depends on slepton lifetime: prompt decay: 2, 4 or 6 leptons + E

decay in detector: tracks with large impact parameters or kinks + E (+ 2 or 4 leptons)

decay outside detector: tracks with anomalous dE/dx + E (+ 2 or 4 leptons)

l=e ,

(plus tchannel diagrams)

NLSP


GMSB (OPAL): Pair Production with NLSP

● Zero lifetime (l.t.): acoplanar leptons Abbiendi et al., Eur. Phys. J, C32 (2004) 453 Irreducible BG from WW productionh

● Short l.t.: tracks with large impact parametersh

● Medium l.t.: tracks with kinks refit of kink vertexh

BG for short & medium l.t.: cosmics and beam gas/wall events twophoton ( = O(10nb))

h

● Long l.t.: tracks with anomalous dE/dx basically BG free topology

G

ll+

G

kink

large d0

tracking chamber

l l


● No significant excesses observed limits on production cross sections, sparticle masses and model parametersg

● Theoretical framework based on Dimopoulos, Thomas, Wells; Nucl. Phys. B488 (1997) 39g

● mG = 2 eV ⇔ BR( NNLSP X) ≈ 0

g

● √F is eliminated by lifetime independence of experimental cross section limitsg

● Parameter scan:

● Minimal expected ⋅BR2 calculated for each slepton and neutralino mass: (⋅BR2)min

GMSB (OPAL): Parameter Scan

G

Parameter Scan points Step size 5 − 150 TeV 1 TeV tan 1 − 50 0.2 M 1.01, 250 TeV, 106 TeV N 1, 2, 3, 4, 5 sign() +1, 1


crossing of dE/dx bands of sleptons & SM particles

GMSB (OPAL): Pair Production with NLSPl l

● SUSY MC produced with SUSYGEN or DFGT in masslifetime grid

● Combination of analyses for different lifetimes taking overlaps into account

● √s = 189 209 GeV, ∫L 600 pb1

Combination of √s bins with (⋅BR2)

min

● Statistical treatment according to Junk; Nucl. Instrum. Meth. A434 (1999) 435

● Statistical and systematic errors included

● Similar limits O(0.1pb) in slepton coNLSP scenario


● Comparison of 95

with (⋅BR2)min

⇒ slepton mass limits

m 1 87.4 88.2GeV

m R 93.793.6GeV

● Slepton coNLSP scenario: sleptons degenerate within mass ⇒

m − ml 91.9GeV

GMSB (OPAL): Pair Production with NLSPl l


Topology in detector depends on neutralino lifetime: prompt decay: photons + E (+ leptons/jets)

decay in detector: nonpointing photons + E (+ leptons/jets)

decay outside detector: E (+ leptons/jets)

(plus schannel)

(plus tchannel diagrams)

GMSB (OPAL): Neutralino NLSP Topologies


● Combination of √s bins: Chargino pairproduction: ~ /s Slepton pairproduction: ~ 3/sg

● Minimization in neutralino lifetime lifetimeindependent cross section limits

GMSB (OPAL): Indirect Prod. with NLSP

neutralino NLSP chargino pp

Chargino & slepton pairproduction:

● Long lifetime: photons not visible, higher E

● Short lifetime:

neutralino NLSP stau pp

10 1

0


> 40, 27, 21, 17, 15 TeV for N = 1, 2, 3, 4, 5(N = number of messenger generations) m

h > 114.4 3 (theo) 5 (m

t) GeV

GMSB (OPAL): Interpretationsign() > 0

Lifetimeindependent limits on :

Lifetimeindependent exclusionsin GMSB parameter space:

ADD model ● n large compact extra spatial dimensions● we live in 4 dimensions ("on the brane"), gravity can propagate in the 4+n dim. bulk● gravitational mass scale M

D in D = 4+n dimensions is of the order of the weak scale

● effective MP in 4 dim. is large only due to the hidden volume Rn of the extra dimensions:

● for n=1, R ~ 1013cm ≈ distance between earth and sun astronomically excluded● for n=2, R ~ 100m not excluded yet


Extra Dimensions (ED) Motivation

Hierarchy between electroweak scale MEW

and Planck scale MP explained by

two popular models: the ADD model (ArkaniHamed, Dimopoulos, Dvali) and the Randall Sundrum model

M P2≈M D

2n Rn

(Phys. Lett. B429 (1998) 263272)

Phenomenological consequence of EDs: ● massive excitation states of the graviton: "Kaluza Klein" (KK) tower● in ADD framework: large multiplicity of states, gravitiational interaction with SM particles, invisible


Single & Multiphoton Events with E (L3)

● Single Graviton production at LEP:

⇒ single photon plus E signature

d 2dxd cos

=

32 sn /2

n /2 s

M D

n2

f x , cos

(Guidice, Rattazzi, Wells; Nucl. Phys. B544 (1999) 3)

= polar angle, x = E

/E

beam, = finestructure constant

● Background from and e e− e e− e e−



● High energy singlephotons: pT > 0.02 √s

purity for = 99.1% ⇒ N

obs / N

exp = 1898 / 1905.1

● Low energy singlephotons: 0.008 √s < pT < 0.02 √s

one photon candidate in the barrel (single trigger) ⇒ N

obs / N

exp = 566 / 577.8

● Photon candidates must have E > 1GeV

● Two event topologies are studied:

e e−

low E single

● Theoretical differential cross section ⇒ number of exp. signal events as function of (1/M

D)n+2

⇒ limits on MD from fit to x

vs. cos

distribution

high & low E single



● LEP combination including ADL: LEP Exotica WG 200403h

● For each n, the log likelihood functions are added and limits calculated using Bayesian likelihood method


Search for one large ED (Delphi) ● ADD limits from singlephoton signature for n > 1 onlyg

● But n = 1 allowed for a slightly warped geometry: based on RS1 type model, but no light KK modes (Guidice, Plehn, Strumia; Nucl. Phys. B706 (2005) 455) g

● Photon energy spectrum depends strongly on n new analysis necessary

● Expected number of singlephoton events in DELPHI electromagn. calorimeter ● Corrected for cal. efficiency & resolution

n=

n=


Search for one large ED (Delphi)

⇒ MD ≥ 1.69 (1.71) TeV 3% for n = 1

● Final event selection with likelihoodratio based on E

● Preselection of singlephoton events using tracker and ECAL (√s=183209 GeV, ∫L=650 pb1)g

High density Projection Chamber (HPC) x

> 0.06

Forward ElectroMagnetic Cal. (FEMC) x

> 0.10

Small angle TIle Calorimeter (STIC) (BG dominated not used for final analysis)

Nobs

Ne+e () Nother SM BGg

FEMC 705 623 ± 3 49.1g

HPC 498 540 ± 4 0.6


Search for Branons (L3)● ADD type geometries: brane oscillations corresponding to a brane tension = f4 ⇒ New scalar fields = Goldstone bosons corresponding to the SSB of the translational invariance produced by presence of the brane: "branons"g

● Translational invariance is not exact branons are massiveg

● For tension scale f << MD, Gravitons decouple from SM particles

(e.g. Cembranos , Dobado, Maroto, Phys. Rev. Lett. 90 (2003) 241301)


Search for Branons (L3)● + E and + E covered, but low sensitivity in Z channel due to phase space ● Two different analysis for + E, depending on p

T:

High pT:

0.04 Ebeam

< pT < 0.6 E

beam

purity for = 99%

⇒ Nobs

/ Nexp

= 838 / 811.2(N

s = 351.4 for M = 0 and f = 150GeV)

e e−

Low pT:

0.016 Ebeam

< pT < 0.04 E

beam

barrel only (photon trigger!) BG mainly from

⇒ Nobs

/ Nexp

= 543 / 554(N

s = 95.3 for M = 0, f = 150GeV)

e e− e e−

√s = 189209 GeV, ∫L 630 pb1

Z q q


Search for Branons (L3)● One light branon with mass M assumedf

● Efficiency for branons from SM MCs for and , reweighted with diff. cross section from Alcaraz et al. (Phys. Rev. D67 (2003) 075010)f

● Binwise comparison of observed and expected number of events for x vs. cos distribution, assuming Poisson probability distribution

M > 103 GeV

f > 180 GeV

e e− Z q q e e−


Summary● No evidence for new physics observed in searches for GMSB signatures and extra dimensions ⇒ Limits on slepton and neutralino masses as well as on the SUSY mass scale within the GMSB scenario:

⇒ Limits on gravitational mass scale MD

in extra dimensions: M

D > 1.69, 1.60, 0.66 TeV for n = 1, 2, 6

● LHC startup very soon – discoveries might be just around the corner!

generator level, signal only

> 40, 27, 21, 17, 15 TeV for N = 1, 2, 3, 4, 5

20 1

0 Z0

20 1

0 l− l

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Search for SUSY and Extra Dimensions at LEPklein/ichep.pdf · Search for SUSY and Extra Dimensions at LEP. Outline Four abstracts submitted: Supersymmetry f Searches for gaugemediated