SUSY or UED

1
SUSY or UED?
Update
21/9/07
Tom Byatt
(Alan Barr)
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Introduction/Reminder

• What if there was confirmation of something?
  What is it? SUSY? or Universal Extra
• Dimensions (UED)?

• UED appears to have very similar collider
  signatures to those of SUSY.
• (Bosonic Supersymmetry).

• A way to distinguish between the two
  physically-motivated models is therefore needed.

• Exploit the difference in their spins. SUSY
  differ by 1/2 a unit, UED identical spin
• quantum numbers to their SM counterparts.

• A novel such method (Barr,A.J., hep-ph/0511115)
  was proposed recently whereby a
• measurement of the spins of sleptons in the
  direct di-slepton pair production process

(SUSY)
would offer a way to differentiate between the
two models, namely SUSY UED.
(UED)
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• Both give signature
• - 2 Opposite Sign Same Flavour (OSSF) leptons
  (ee- or µµ- only),
• - ,
• - little/no jets (ISR).

gt So need a variable which is sensitive to the
slepton production angle.

• Cosine ll - cosine of the polar angle between
  each lepton and the beam,
• in the longitudinally boosted frame in which the
  pseudo-rapidities of the
• leptons are equal and opposite.

?

• 1-D function of , better because
• All benefits of
• Interpretation as angle in long. boosted frame
  (simpler geometrically)
• Easier to compare with theory

• Advantages of

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In the Summertime, When the Weather Is Wet

• Copied over remaining datasets from the Grid.

(Thanks Catrin? )

• rel 11 and rel 12 correctly normalised when
  added.

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Optimisation of cuts

• Looked at migrations at cut boundaries of 6
  distributions.

Mt2-Primarily to remove WW bgd. Used for cases
when same mass particles are pair produced and
decay semi-invisibly.

• Vary 3 of them, MT2, Mll and MET .

(hep-ph/9906349 and hep-ph/0304226)

• In doing this, maximise the quantity

(Neymann-Pearson Lemma)
-gtto test to what extent which model/hypothesis
is true (ability to distinguish between

the 2 models,
SUSYand UED).
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• Scanned 100 points in 3D parameter space.

Default cuts Jet PT(1)lt100GeV LeptonPT(1,2)40GeV
, 30GeV Transverse Recoil lt100GeV

• Final ffm 23.621 (3dp)

MT2gt 77GeV, Mll gt 116GeV, METgt 101GeV
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Plans Present Foreseeable Future

• Determination of the SM backgrounds. Various
  methods to employ.

• (i) Use idea of control sample or control
  region-gt regions of PS in which
• a particular background dominates.

• Using these enriched bgd samples -gtcan measure
  bgd well and precisely
• and importantly extrapolate to another
  kinematical region.
• Caveat to ensure no biasing introduced.