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Split SUSY at Colliders

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Title: Split SUSY at Colliders


1
Split SUSY at Colliders
Durham University
  • Peter Richardson

Work done in collaboration with W. Kilian, T.
Plehn and E. Schmidt, Eur.Phys.J.C39229-243,2005,
hep-ph/0408088.
2
Introduction
  • We have had a lot of talks on Split SUSY and the
    theoretical motivations (or lack of them.)
  • I will not repeat those arguments now.
  • From a phenomenological point of view Split SUSY
    is interesting because it predicts very different
    collider signatures.
  • We need to investigate these signatures to ensure
    we don't miss SUSY if its there.

3
Introduction
  • In Split SUSY due to the high mass scale the only
    SUSY particles which can be produced in colliders
    are
  • Gluinos
  • Charginos
  • Neutralinos

4
Hadron Collider Signals
  • At hadron colliders the only production
    mechanisms are
  • Gluino pairs
  • Gaugino pairs
  • due to the large scalar masses associated
    production mechanisms are negligible.
  • The signals from the gauginos may be observable
    but it is hard at both the Tevatron and LHC
    unless the masses are close to the LEP limits.

5
Gauginos at Hadron Colliders
  • For a sample Split SUSY point with
  • The masses are

6
Gauginos at Hadron Colliders
  • The dominant cross sections are
  • 2910fb
  • 1498fb
  • 2099fb
  • The trilepton signal is hard as the decay
    is mediated by the Z.
  • Other modes might be possible.

7
Gluinos at Hadron Colliders
  • There is however a large cross section for the
    production of gluino pairs.
  • In the Split SUSY model this only depends on the
    mass of the gluino.
  • There are three scenarios
  • Gluino decays promptly
  • Gluino decays in the detector.
  • Gluino is stable on collider timescales

8
Gluinos at Hadron Colliders
  • The first two scenarios should be similar to the
    models already studied, with the addition of
    displaced vertices in the second case.
  • Therefore we studied the case of the stable
    gluino.
  • There have been previous studies of this for the
    Tevatron Baer, Cheung, Gunion PRD 59,075002 and
    we used many of the same ideas.

9
Gluinos at Hadron Colliders
  • When the gluino hadronizes it will form either
  • Glueball-like state
  • Mesonic state
  • Baryonic state
  • General opinion is that
  • Rg is the lightest state
  • Rqqq is unlikely to be directly produced.

10
Gluinos at Hadron Colliders
  • We included the production of these states in the
    cluster hadronization model of HERWIG.
  • Due to the modelling of the hadronization the
    relative probability, ,, of producing the
    gluonic and mesonic R-hadrons is undetermined.
  • This parameter and the gluino mass determined the
    phenomenology at hadron colliders.

11
Gluinos at Hadron Colliders
  • There are two signals we considered
  • Charged R-hadron production
  • Signal much like stable weakly interacting
    particles.
  • R-hadron looks like a muon but deposits more
    energy in the calorimeter.
  • Arrives later at the muon chambers due to the
    mass.
  • Can measure the mass using the time-delay.

12
Gluinos at Hadron Colliders
  • Neutral R-hadron production
  • Some energy loss in calorimeter
  • Monojet type signals
  • In both cases we used HERWIG interfaced to
    AcerDet for fast detector simulation together
    with simple modelling of the R-hadron
    interactions based on Baer, Cheung, Gunion PRD
    59,075002.

13
Energy Loss
  • We used a range of different models of the
    hadronic cross section to estimate the
    uncertainty of this simple approach.
  • The more accurate results of Kraan hep-ex/0404001
    are within this range.

14
Energy Loss
15
Charged R-hadrons
  • Applied a simple efficiency for reconstruction
    for 85 as with muons.
  • Required the charged R-hadron to have transverse
    momentum greater than 50 GeV.
  • The time delay at the muon detectors between 10ns
    and 50 ns.
  • Required the observation of 10 events.

16
Charged R-hadrons
17
Mass Measurement
18
Mass Measurement
19
Neutral Searches
  • The neutral search was based on an optimised
    analysis using the same cuts as the experimental
    analysis in Barr et. al. JHEP 0303045,2003.
  • This requires at least 100 GeV missing transverse
    energy and one jet with transverse momentum
    greater than 100 GeV which should be sufficient
    to pass the trigger.

20
Neutral Searches
21
LHC
  • Charged R-hadron signal can be seen up to above 2
    TeV.
  • Neutral signal is worse.
  • Needs more detailed experimental study.
  • There have been other studies
  • Hewett et. al. JHEP 0409070,2004 considered the
    charge flipping which we neglected.
  • STOPPING GLUINOS.
  • Arvanitaki et. al. hep-ph/0506242 consider
    gluinos which are stopped in the detector.

22
ILC
  • Chargino and Neutralino sector is the same as
    usual.
  • Masses can be extracted using standard
    techniques.
  • The integrating out of the heavy degrees of
    freedom leads to different neutral/chargino
    Yukawa couplings.

23
ILC
  • Assume mass measurements to 0.5
  • Cross sections with statistical error only.
  • Fit the anomalous Yukawa couplings.
  • At larger values possible to distinguish
    weak-scale MSSM from SpS.

24
Conclusions
  • Split SUSY has different and interesting
    experimental signals.
  • Should be observable at the LHC for gluino masses
    less than 2 TeV.
  • At a linear collider can be verified by looking
    at gaugino yukawa couplings.
  • In general looking at the gaugino yukawa
    couplings would be an interesting test of the
    MSSM.
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