the search for extra dimensions at present colliderscern.ch/sask/phd/doc/ed05.pdf · the search for...

The Search for Extra Dimensions at Present Colliders

Stefan Ask(Lund University / DELPHI)

Stefan Ask, Lund University The Search for Extra Dimensions at Present Colliders

ALEPH DELPHI

L3OPAL

Stockholm, 2005

� Graviton Emission� Virtual Graviton Exchange� Branon Search� Gauge boson KK modes� TeV String Search� Radion Search� Graviton Resonances

Studies

Outline Introduction

Stefan Ask, Lund University

Graviton Emission

Graviton Exchange

Branon Search

Radion Search

� ALEPH DELPHI L3 Final Results

� ADLO Combined Results

� L3 Results� OPAL Results

ADD Scenario

ADD Scenario

ADD Scenario

RS Scenario

� ADL Combined Results

Main Data Sets

�� 0.6 fb� 1 �

Exp.

E CM

� 189 � 209 GeV

All Limits Computed at 95 % CL

e

e

The theoretical scenarios

TeV String Search

� L3 Results

(ADD Scenario)

LEP

�� 0.2 fb

� 1 �

Exp.

E CM

� 1.96 TeV

Tevatron (Run II)�� 0.1 0.016 fb

� 1 �

Exp.

E CM

� 301 � 319 GeV

HERA (e+ [e-])

p

�

p

p e

�

� CDF D0 Results

� CDF D0 H1 ZEUS Results Graviton Resonances

� CDF D0 Results

RS Scenario

Gauge Boson KK modes

� D0 H1 Results

(ADD Scenario)

The Search for Extra Dimensions at Present Colliders Stockholm, 2005


Extra Dimensions and Branes

Brane

SM particles confined to the brane Gravity propagates in whole D-dim space (Non-SM Gauge bosons propagates in some extra dim)� Gravity weak on the brane since it acts in a

more extended space than the brane

M � M D ,

�

w

� 1 TeV

“ Solves” the hierarchy problem

� Brane picture suggested by several String Models

� Gravity Phenomena appear at,

M

�M P

Brane with 3 Spatial Dimensions in Bulk with D-3 Additional (Extra) Dimensions

Bulk

Mainly Two Brane Scenarios Studied

� The Randall-Sundrum scenario (RS1)

� The ADD Scenario



Gravity Phenomena in 4-dim (on the brane)

Effective 4-dim Theory below M

� Massive KK spin-2 gravitons,

� Massive KK scalar gravitons,

Possible particles related to the brane dynamics

G� �n

H n

� Massive scalar branons,

Including the Radion (n=0)��

D

Finite Size + Escaping momentum appearing as mass on the brane

Graviton Kaluza-Klein Modes (KK-tower)

mKK2 � �

pd2

d, d � 4,..., D

Compactified Extra Dimensions

Particles Searches � The Randall-Sundrum scenario (RS1)

� The ADD Scenario� Spin-2 graviton (Rigid brane)� Branons (Flexible brane)

� Spin-2 gravtion� Radion



The ADD Scenario (Large Extra Dimensions)(* N. Arkani-Hamed, S. Dimopoulos, G. Dvali)

Extra dimensions are � Compactified (normally assumed on a torus and with equal radii, R) � Large (R up to about 1mm)

Gravity Experiment, Cosmology and Astrophysical Constraints

1-dim, Newton's law would be changed at solar system distances

2-dim, Strong bounds

> 2-dim, Relatively weak bounds

e

�

e

"! G

#%$

&%'

M D

Rigid Brane

e

�

e

)( G

*( ff+-, ,

&%.

M D

Flexible Brane

e

/

e

0)1 2�3 2�3 4%5 6

ZGraviton processes exponentially suppressed, e

7 M D2 s 1 7 x8 4 2 9 2

: Dense KK-tower

M D

; 1 TeV

: No hierarchy due to large volume of the compactified space <

mKK

= 1 >R

M P2? 8 @ R n M D

n

A 2Assumed torus shape

Processes (at LEP)

Brane tension

Graviton Emission:

Graviton Exchange:

Branon Production:

Model

Bounds



The Possible Signals at LEP (ADD)e

B

e

C"D G

E%F

d 2G

dxH d cos

IH J sn

M Dn

K 2 F n , xH ,

IH

e

B

e

C"L G

ML ff

N-O Oe

P

e

Q"R S�T ST U%V WZ

M D

X 1.5 TeV

n Y 2

Single photon process directly sensitive to the fundamental scale of gravity (M

D)

and the number of dimensions (n).

Fermion and photon pair process sensitive to cut-off mass scale (M

H)

and the coupling (λ ).

Branon process sensitive to number of branons (nb),

branon mass (Mb) and brane tension (f).

Z Photon distributions similar to Graviton emission process

d 2[dx\ dcos

]\ ^ nb_8 F M b , x\ , s G x\ ,

]\

nb

` 1 Used in the analysis

acb d 1 Used in the analysis

d e

dcos

f g F h i

M H4

(* G.F. Giudice, R. Rattazzi and J.D. Wells; E.A. Mirabelli, M. Perelstein and M.E. Peskin) (* J. Hewett ; K. Agashe and N.G. Deshpande)

(* J. Alcaraz, J.A.R. Cembranos, A. Dobado and A.L. Maroto)

x γ =


The Signals at HERA and the Tevatron (ADD)

Graviton Emission Virtual Graviton Exchange(Similar to ) (Similar to )e

j

e

kml G

npo e

q

e

rts G

us ffv)w w

CDF + D0: mono-jet + missing ET

[ n , MD

] [ λ , MH

cut-off ]

qx

q y G z y ff

{}| |CDF + D0: High mass ee, µµ, γγ

e

~

q � G

� � e ~

q

H1 + ZEUS: High Q2 DIS


(* G.F. Giudice, R. Rattazzi and J.D. Wells)

(Drell-Yan like)

(Neutral-current like)

q

�

ql G

n

g

q g y G �

q

g g y G �

g



ADLO : Graviton + γ Production

Low-energy photon selection

barrel only

Good Agreement between Data and SM Expectation for ALEPH, DELPHI, L3 and OPAL

Results using year2000 & 1999 data not available yet.

Graviton Signal would Appear

L3



ADLO: Graviton + γ Production

ALEPH DELPHI L3

[ Obt. (Exp.) ]Final M Limits (TeV)

n23456

1.26

0.95

0.77

0.65

0.57

1.31 (1.27)1.02 (0.98)

0.82 (0.80)

0.67 (0.67)0.58 (0.58)

1.50 (1.49)1.14 (1.12)0.91 (0.89)

0.76 (0.75)0.65 (0.64)

78

---

---

--- ---

0.57 (0.56)0.51 (0.51)

D

No Indications of a Signal

ALEPH and DELPHI show a similar sensitivity whereas that of L3 is higher



Combined: Graviton + γ

�

x � �

x ALEPH � �

x DELPHI � �x L3

CL ��

0

x 95 �x dx�

0

� �x ' dx '

� 0.95

1/(M )n+2 M

(TeV)n23456

-0.02 +/- 0.08

-0.09 +/- 0.22

-0.3 +/- 0.8

-0.9 +/- 3.3

-4.8 +/- 15.2

> 1.60 > 1.20> 0.94

> 0.77> 0.66

DD

Measurement of scaling factor, x = 1/(M )n+2

DSc

ales

the

sign

al

Combined Likelihood

ADL Combined Limit


CDF/D0 : Graviton + Jet Production

M

(TeV)n23456

> 0.89 > 0.73> 0.68

> 0.64> 0.63

D

Tevatron Run I Limits

M

(TeV)

> 1.00

> 0.77

> 0.71

D

[> 0.68]

[> 0.67]

[> 0.66]

[Preliminary Run II Results]

CDF D0

Stefan Ask, Lund University The Search for Extra Dimensions at Present Colliders Stockholm, 2005

p

�

p � Jet

�

E T

Combined: Graviton + γ


G N

� 1� 8 � R n M Dn

� 2Assuming torus shaped extra dimensions

(D0/CDF results are based on Run I data only)

� LEP limits increasingly stringent with lower number of extra dimensions compared to the D0/CDF results

n R mm

23456

< 0.19< 2.6x10-6

< 1.1x10-8

< 4.1x10-10

< 4.6x10-11



ADLO: Virtual Graviton ExchangeFit to LEP combination of the differential Bhabha and photon pair cross section

M H

� 1.20 TeV

�� 1M H

� 1.09 TeV

� � � 1

e

�

e

�� e

�

e

�x H

� �

M H4

M H

� 0.93 TeV

�� 1M H

� 1.01 TeV

�� 1

e

�

e

�"� � �(Fit-Parameter, )

DELPHI


CDF/D0+H1/ZEUS : Virtual Graviton Exchange

0.82

0.78

0.78

0.79

M H

¡ 0.96

1.28

M H

¡ 0.99

1.16

CDF / D0 H1 / ZEUS

Mee =475 GeVD0


q

¢

q £ G ¤ £ ee

}¥ ¥

q

¢

q £ G ¤ £ ee

D0:

CDF: e

¦

q § G

¨ § e ¦q

TeV

©�ª «1TeV

¬� ® 1

H1 / ZEUS:



L3: Branon Searche

¯

e

°"± ²�³ ²�³ ´%µ ¶

Z

·¹¸ 180 GeVº¹» 47 GeV

M b

¼ 103 GeV

M b

¼ 54 GeV

M b

½ 0 ¾À¿ 0ÁmÂ ÁmÂÃ :ÁmÂ ÁmÂ Z :

Ä Single Z signature events (Unbalanced hadronic events with visible mass compatible with m

Z)

Å Single photon events (as for the G+γ search)


D0+H1: Gauge Bosons in TeV -1 Sized Extra DimensionsPhenomenological study from existing data


Dedicated searches:

MC > 1.12 TeV M

C > 1.0 TeV

If gauge bosons have access to (ADD like) extra dimensions of the size, R Æ M C

Ç 1È TeV

Ç 1

Gauge bosons with mass, M KK2 Æ m0

2 É n2

R2

E.g. Ê

n Ë 0 Ì Ê

SMÍ

n Î 0 Ï mÐ

n '

Ñ n' M C

assumed M C

Ò

s

“ Contact interactions” (virtual contributions)

D0 H1 qÓ

q Ô ee(similar to the virtual graviton analysis)

e

Õ

q Ö e Õ

q (NC)

(One extra dim.)


(* K. Cheung, G. Landsberg)


L3: TeV String Search

× Effect on Bhabha scattering of TeV scale strings

d Ø

dcos

Ù Ú d Ø

dcos

Ù

SM

F M S

2

(* S. Cullen, M. Perelstein and M. Peskin ; E.Accomando, I. Antoniadis and K. Benakli)

M S

Û String scale Û 1.6 Ü 3.0 Ý

M D

String model with ADD extra dimensions

× This TeV string effect would typically dominate over virtual graviton exchange

M S

Þ 0.55 TeV

MS = 0.42

Obtained Limit



The RS Scenario (RS1)(* L. Randall and R. Sundrum)

Two Branes: ß SM confined to one brane (SM-brane)ß Gravity concentrated to the other brane (Planck-brane, due to “warped” geometry)

One Extra Dimension: (between the branes)ß Gravity exponentially damped with increasing distance from the Planck brane

ß Local fluctuations of inter-brane distance

Weak gravity on SM brane

The Radion, massive scalar

Planck SM

ds2à e

á 2kr c

âäãæå ç dx

å

dx

çéè

r c2 d

ê 2

5th-Dim y=r

cφ

(xµ)

Gravity exponentially damped by “warp-factor”

Non-factor izable “ warped” geometry

rc = Compactification radius (VERY small)

φ = 0 φ = π

ß Small rc and sizable graviton coupling

Spin-2 Graviton Resonancesëíì M P e

î k r C

ïñð TeVGravity Scale:


Radion have same Quantum Numbers as the Higgs

ò Higgs – Radion mixing, into one Higgs-like and one Radion-like state (h & r)

Both h and r are mainly produced at LEP in the “Higgs-strahlung” process

e

ó

e

ô�õ Z

ö

h

÷

r

Which depends on the RS parameter space øúù Mixing parameterû ù Mass scale on SM brane

mh

ü Mass of Higgs ý like state

mr

ü Mass of Radion ý like state

(* C. Csaki, M.L. Graesser and G.D. Kribs)

The RS Scenario

First Graviton KK mode ( ) willbe in the order of a TeV

Gþÿ n � 1

ò LEP and HERA are insensitiveò Possible graviton resonance at the Tevatron

q�

q � G

� � f f

��

on-shell

Which depends on the RS parameter space

kM P

� Curvature parameter (0.1-0.01 allowed)

m1

ü Mass of first graviton KK mode

Stefan Ask, Lund University The Search for Extra Dimensions at Present Colliders Stockholm, 2005


OPAL: Radion Search

Searches used:� Standard Higgs search

� Hadronically decaying Higgs search

� Decay mode independent Higgs search

e

e

� Z �

h

r

e

�

e

�� Zh , h� bb

e

�

e

�� Zh , h� xx

e

�

e

�� Zh , h� qq

�

gg

� Excluded parameter space obtained by a parameter scan

� Point excluded if signal cross section exceeds the limit from any one of the three searches

Radion process suppressed with increasing Λw

and at large negative mixing

Radion

Higgs



OPAL: Radion Search

Overall Higgs Limit

mh

� 58 GeV Obtained

mh

� 54 GeV Expected

Not possible for the radion state due tosuppressed couplings with increasing Λ

w

and decreased cross section at large negative mixing

The search is sensitive to the h signal over the whole parameter space


CDF/D0: Graviton Resonance


q

�

q � G

� � e e

�� q

�

q � G

� � e e

�� D0 CDF

m1 Limits (CDF / D0)

m1

� 700

�

785 GeV

m1

200

!

300 GeV

k

"

M P

# 0.1

k

"

M P

# 0.01


m1= 300 GeV

Conclusion


$ Several extra dimension models have been investigated at LEP, HERA and the Tevatron, but no indication of a signal has been observed

M

(TeV)n23456

> 1.60 > 1.20> 0.94

> 0.77> 0.66

D

G

%'& Jet G

( ) ff

*,+ +

M H

- 1.28 TeV

.0/ 1 1M H

- 1.16 TeV

.0/ 2 1

354 354 6'7 8

Z

9;: 180 GeV

M b

< 103 GeV

M b

= 0>@? 0

Z

A

h

B

r

mh

C 58 GeV

$ The results give many important constraints on models with extra dimensions, however much remains to be investigated at the LHC !

Exclusion Limits

ADD TeV String

M S

D 0.55 TeV

eE

e

F�G e

E

e

F

RS

KK Modes

MC > 1.12 TeV

q

H

q I ee

m1

J 300 GeV

k

K

M P

L 0.1k

K

M P

L 0.01m1

J 785 GeV(M

C > 6.6 TeV)

(LEP EW)G n M 1 N Resonance

[> 0.71]


(most stringent)

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