Post on 22-Dec-2015
Split Supersymmetry: Signatures of Long-Lived
Gluinos
• Intro to Split SUSY• Long-Lived Gluinos @ LHC• Long-Lived Gluinos in Cosmic Rays
JLH, Lillie, Masip, Rizzohep-ph/0408248
SUSY05 Durham J. Hewett
Split SUSY Intro & Philosophy– See Savas Dimopoulos, Thurs plenary
Arkani-Hamed, Dimopoulos hep-ph/0405159
Giudice, Romanino hep-ph/0406088
Split SUSY Collider Phenomenology– See SUSY/Higgs Parallel, Friday afternoon Numerous authors & papers!
Split SUSY Dark Matter– See Astro Parallel, Wed afternoon Numerous authors & papers!
Split Supersymmetry: Philosophy
• SUSY is irrelevant to the hierarchy problem– Cosmological constant problem suggests fine-tuning
mechanism may also apply to the gauge hierarchy
• Break SUSY at the GUT scale– Scalars become ultra-heavy (except 1 light Higgs): mS ~ 109-12 GeV
– Fermions protected by chiral symmetry
• Phenomenological Successes:– Retain gauge coupling unification
– Higgs mass predicted to be `heavier’: mH ~ 120-150 GeV
– Flavor & CP problems are automatically solved– Proton decay is delayed (occurs via dimension-6 operator)
• Collider signatures & Dark Matter implications substantially different!
• Whether you buy into this program or not, it behooves us to examine the collider signals of Split SUSY
• We don’t know what the LHC is going to discover and we need to be prepared!
Gauge Coupling Unification: (See Dimopoulos)
1 TeV MSSM @ 1-loop
Split SUSY @ 1-loop
mS = 109 GeV
Arkani-Hamed, Dimopoulos hep-ph/0405159
Higgs Mass Prediction: (See Dimopoulos)
mH = 130-170 GeV for mS > 106 GeV
Measurement of gaugino Yukawas determines SUSY breaking scale
Arvanitaki, Davis, Graham, Wacker hep-ph/0406034
Higgs Mass @ 1-looptan = 50
1
Error bands reflect mt & s errors
LSP (10) is still dark matter candidate (See
Dimopoulos)
10
10
10
10
hf,V
f,V(*)-
V
V(*)
Main annihilation channels:•No scalar exchange•depends on fewer parameters
Points which satisfy WMAP relic abundance constraint
Pierce, hep-ph/0406144
+ co-annihilation graphs very efficient!!
Collider Phenomenology: EW Gauginos
• Produced in pairs via Drell-Yan 1
0 is LSP• Only open decay channel:
(20)
W (Z)
10
No cascade decays!
Tri-lepton signature sill valid, exceptGaugino couplings (at the TeV scale) are smaller than those in MSSM
GUT tests require accurate coupling measurements @ ILC
Collider Phenomenology: Gluinos
• Pair produced via strong interactions as usual• Gluinos are long-lived• No MET signature• Interesting detector signatures
g~q~
q
q
10
Gluino lifetime:
ranges from ps to age of the universe for TeV-scale gluinos (Cosmological constraints)
JLH, Lillie, Masip, Rizzohep-ph/0408248
Gluinos as LSP:Baer etal 1998
~ ps, decays in vertex detector•ps < < 100 ns, decays in detector > 10-7 s, decays outside detector bulk of parameter space!
Gluino Hadronization and Fragmentation
Gluino hadronizes into color singlet R-hadron
• R is neutral: energy loss via hadronic collisions as it propagates through detector
• R is charged: energy loss via hadronic interactions and ionization
• R flips sign: hadronic interactions can change charge of R, can be alternately charged and neutral! ionization tracks may
stop & start!
Fragmentation is uncertain: slight preference for neutral R-hadrons
Prob < Prob
m - m > m
Energy Loss in the Detector
• Hadronic Interactions: RN RX
– model with constant differential or triple pomeron– deposits few 100 MeV per interaction
Mean interaction length: ~ 19 cm in Fe 100 GeV R with E = 400 GeV, deposits at most 6.4 GeV in CDF
• Ionization: Bethe-Bloch Eqn– sizeable energy loss for slow moving R-hadrons– fast moving R-hadron deposits ~ 1.5 GeV
~ k
k typically ~ (0.1-0.35 GeV)
Either case: amount of energy deposition may escape triggers!
Interactions due to light constituents energy loss E ~
Searches:
1. Stable, neutral R-hadron: most challenging case!• Energy loss via hadronic ints unobservable• Consider Gluino pair + jet production
• Trigger on high pT jet
• Since scalars decouple, use QQ + jet productionMonojet Searches:CDF:
One central jet ET > 80 GeV
MET > 80 GeVRun I 284 events observed 274 16 expected New Physics < 62 events
Mgluino > 170 GeV
215 GeV (scaled Run II with 1 fb-1)
LHC: one central jet ET > 750 GeV MET > 750 GeV expect ~ 4200 bckgnd events
Mgluino > 1.1 TeV for 100 fb-1
Gluino pair + jet cross section
Tevatron Run II (1 fb-1) LHC
At LO with several renormalization scales
2. Stable, charged R-hadrons:– time of flight for slow moving (relative to = 1)
ranges from 0.8 (m = 200 GeV) to 0.4 (m = 500 GeV) @ Tevatron
– high ionization energy loss for fast moving
charged R-hadrons can be tracked as they traverse the detector– Consider only gluino pair production w/o bremstrahlung
– CDF:Heavy charged stableParticle search yieldsmgluino > 270 GeV (Run I)
430 GeV (Run II with 2 fb-1)
Ionization loss (dE/dx) for ≤ 0.85:Mgluino > 300 GeV (Run I)
LHC: Scale CDF results mgluino > 2.4 TeV
3. Alternating sign R-hadrons (flippers)– Re-fragmentation after every hadronic interaction– highly model dependent!!!– worst case scenario is monojet signature from 100%
neutral R-hadrons– Signature: off-line analysis of monojet signal
reveal charged tracks that stop & start puffs of ionization energy deposition!
R-hadrons in Cosmic rays: Signatures in IceCube
• p+N gluino pairs• R-hadrons form• interact with
nucleons in atmosphere & ice
• Showering R-hadrons very energetic!
• Deposit ~ TeV in atmosphere
• Deposit ~ 40 TeV in IceCube
Summary
• Split SUSY predicts novel collider (& cosmological) signatures
• Gaugino decays differ substantially from MSSM• Need to re-examine gaugino searches• Worst case scenario: R-hadron neutral & stable
– Tevatron search reach up to mg ~ 270 GeV
– LHC search reach up to mg ~ 1 TeV
• Search reach extended if R-hadrons charged• Cosmic ray signals not quite competitive with
colliders
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