Search for ExtraDimensions at pp and ep Colliders

1
Search for Extra-Dimensionsat pp and ep
Colliders
_

• Eric Kajfasz, CPPM/D0
• kajfasz_at_cppm.in2p3.gov
• for the CDF, D0, H1 and Zeus collaborations

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Extra Dimensions Outline

• Extra Dimension Models and Signatures studied at
  CDF D0 Run II, H1 and ZEUS
• Preliminary results on virtual graviton/gauge
  boson exchange and direct graviton emission
• Summary and Conclusions
• Why ED?
• come naturally with string theory
• provide mechanism to explain why MEW ltlt MPL
• ...

3
Extra Dimensions Models Explored

• focus on n extra dims in models where SM fermions
  live on a D3-brane
• Large Extra Dimensions (LED) Arkani-Hamed,Dimopoul
  os,Dvali Phys Lett B429 (98)
• MPL 1019GeV
• n gt 2 compact and flat - MS
  string/fundamental scale M2PL Rn MSn2 gt MS
  can be lowered to TeV scale
• gravitons propagate in the bulk gt Kaluza-Klein
  tower G(k)
• cant resolve successive modes (0.01eVn2
  1MeVn3 100MeVn6)
• gt expect
• virtual exchange of graviton KK modes
• real graviton emission
• TeV-1 Extra Dimension (TeV-1) Dienes,Dudas,Gherghe
  tta Nucl Phys B537 (99)
• MC compactification scale ( TeV)
• gauge fields can propagate in the bulk gt KK
  towers of gauge bosons
• modes with nearly equal energy spacing TeV
• lower GUT scale by changing running of the
  couplings
• gt expect
• resonances at high energies (LHC ...)
• virtual exchange (Hera, Tevatron)

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Extra Dimensions Models Explored ...

• Warped Extra Dimension (RS) Randull,Sundrum Phys
  Rev Lett 83 (99)
• ED of size R, highly curved, compactified on
  S1/Z2 orbifold y Rf.
• Zero mode graviton G(0) localized at the
  Planck-brane (y 0)
• SM fields localized on TeV-brane (y Rp)
• metric ds2 e-2kRf hmndxmdxn R2df2
  k curvature scalefor kR 11-12, Lp
  MPLe-kRp TeV
• consistency gt 0.01 lt k/MPL lt 0.1
• Gravitons propagate in the bulk gt KK tower G(n)
  of modes of mass mn xnke-kRp (xn 1st Bessel
  func. zeros i.e. 3.83, 7.02, 10.17, ...)gt well
  separated modes
• Lp m1MPL/(kx1) gt model characterized by m1 and
  k/MPL
• gt Look for first graviton resonance

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Extra Dimensions Topologies Explored
Exchange Virtual Gravitons (LED,TeV-1,RS)
Tevatron
Hera
G
jet(s) MET g MET
Emission of Real Gravitons (LED)
q
g(jet),g
Tevatron
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Large Extra DimensionsVirtual Graviton Exchange
dilepton channel (Tevatron)
SM
SM
diphoton channel (Tevatron)
DIS channel (Hera)
SM
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Large Extra DimensionsVirtual Graviton Exchange
s sSM hGsint hG2sKK

• Effect of ED parameterized by a single
  variable
• different formalisms have different definitions
  of MS
• Hewett (Hewett, Phys Rev Lett 82, 4765 (99) )F
  2l/p with l 1
• GRW (Giudice, Rattazzi, Wells, hep-ph/9811291)F
  1
• HLZ (Han, Lykken, Zhang, hep-ph/9811350)F
  log(MS2/s) for n 2F 2/(n-2)
  for n gt 2

hG F/ MS4
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Large Extra Dimensions Virtual Graviton Exchange
ee

• 2 isolated es, ETgt 25 GeV
• es coming from luminous region
• MET significance cut
• eCC 92.4 0.4 eCP 79.2 0.5
• for Mee gt 350 GeV Nexp 4.6, Nobs 8
• Mee distrib. used in binned likelihood gt Limits
  on hGl/MS4

CCCP
95 CL limits on MS (TeV)
Mee
C(entral) hlt1 P(lug) 1lthlt3
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Large Extra Dimensions Virtual Graviton Exchange
diEM

• diEM combine ee and gg
• 2 EM objects, ET gt 25 GeVwith track isolation
• overall ID efficiency 85 1
• for MdiEM gt 350 GeVNexp 9.7 (1.6 QCD), Nobs
  8
• Systematics 12

200pb-1
CC-CC CC-EC
signal for hG 0.6
D-Y direct gg QCD
QCD
CC-CC CC-EC
CC hlt1.1 EC 1.5lthlt2.4
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Large Extra Dimensions Virtual Graviton Exchange
diEM

• Data agree with SM predictions gt
• MdiEM vscosq distrib. usedin 2D Binned
  Likelihood
• gtSet limits on hG alone orin combination with
  Run I results
• gt give 95 CL limits on MS (TeV)
• Most stringent constraints on LED for n gt 2 to
  date among all experiments.

200pb-1
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Large Extra Dimensions Virtual Graviton Exchange
mm

• 2 ms with PT gt 15 GeV
• isolated, hlt2.0
• cosmic veto
• Mmm gt 50 GeV
• for Mmm gt 300 GeVNexp 6.4 and Nobs 5
• Systematics 13

D0 RunII Preliminary
Mmmvscosq distr. used in 2D Binned
Likelihood gt Set limits on hG gt 95 CL limits
on MS (TeV)
250pb-1
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Large Extra DimensionsHERA Virtual Graviton
Exchange
G(k) Virtual exchange in t-channel interferes
with Deep Inelastic Scattering (DIS) Small
contribution O(1) from eg -gt eg G(k)
exchange affects the Q2 distribution at high Q2
Compare ds/dQ2 to what is expected from SM
Q2 (k-k)2 -q2
,KK
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Large Extra Dimensions Virtual Graviton Exchange
DIS
c2 fit of ds/dQ2 no deviation from SM gt Set
limits on hG gt 95 CL limits on MS (TeV)
Hewett formalism
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Large Extra Dimensions Virtual Graviton
Exchange
DIS
ds/dQ2 used in binned likelihood gt Set limits on
hG gt 95 CL limits on MS (TeV)

• Hewett formalism
• l - 1 MS gt 0.79 TeV
• 1 MS gt 0.78 TeV

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Large Extra DimensionsDirect Graviton Emission
jet(s)MET

• Graviton produced along with a jet disappears in
  the bulk, undetected gt mono-jet like topology
  with high MET

• Nexp 100.2 6.3 (stat) 7.5 (theo)
  50 - 30 (JES)
• Nobs 63 ( 5 efficiency)

• Final Selection
• MET gt 150 GeV
• PT(jet1) gt 150 GeV, h lt 1
• PT(jet2) lt 50 GeV
• Df(MET,jet1) gt 30o

limits on MS 660-680 GeV
85pb-1
QCD
MC SM bkg mostly Z-gtnnjet(s)
updated analysis with 200pb-1 and new JES in
process ...
n 6 and MS 0.7 TeV
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TeV-1 Extra DimensionVirtual Exchange of Z/g KK
states
D0 ee
200pb-1

• (gt 1 EM w/ track match)
• same procedure as for LED analysis but with
  virtual Z/g KK states effects parameterized
  by hC p2/3MC2
• Nexp 12.1 (4.3 QCD), Nobs 9
• gt Limit set as done for LED hC lt 2.63 TeV-2 gt
  MC gt 1.12 TeV _at_ 95 CL

signal for hC 5 TeV-2
QCD
D-Y QCD
H1 DIS
KK states modify the Z/g propagators 1/Q2 -gt
1/Q2 hC 1/(Q2MZ2) -gt 1/(Q2MZ2) hC Fit to
ep and e-p data gt MC gt
1.0 TeV _at_ 95 CL
LEP
from combined precision EW measurements
MC gt 6.6 TeV
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RS Extra Dimension

• Graviton KK states well separated gt resonant
  graviton search
• CDF analyses
• ee and mm binned likelihood method
• gg counting limits using 3s mass window around
  resonance
• D0 analysis
• diEM using 3s mass window method

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RS Extra Dimension
ee, mm, gg

• mm
• 2 isolated ms w/ PTgt20GeV
• hm1 lt1, hm2lt1.5
• cosmic veto

??
ee
??

• gg
• 2 isolated gs w/ ETgt15GeV
• CC

• ee
• 2 isolated es w/ ETgt25GeV
• CC or CP

data agree with expected SM bkg ...
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RS Extra Dimension
ee, mm, gg

• cross-section limits computed from binned
  likelihood (ee,mm) and 3-s mass window (gg)
• compare to R-S cross-section for different
  values of the k/MPL parameter.

??
ee
??
gt exclusion contour plot ...
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RS Extra Dimension
ee, mm, gg
Lower limits on MG (GeV) for k/MPL 0.1

• Further improvement can be achieved by
• using mass window method for dilepton channels
• combining channels

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RS Extra Dimension
diEM
same diEM data set as for LED search
200pb-1
CC-CC CC-EC
signal RS Graviton MG 300 GeV
D-Y direct gg QCD
QCD
785 GeV
data agree with expected SM background gt set
limits with mass window method
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Summary
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Conclusions

• Tevatron, CDFD0 working well
• CDFD0 have by now each 450pb-1 on tape
• Tevatron and HERA are great tools to start
  looking for EDs
• Very competitive results and even most stringent
  limits are starting to come out
• There is still room for improvement, so stay
  tuned.
• However, for the final word on some models, we
  may very well need to wait for LHC ...