- Количество слайдов: 22
Split Supersymmetry: Signatures of Long-Lived Gluinos JLH, Lillie, Masip, Rizzo hep-ph/0408248 • Intro to Split SUSY • Long-Lived Gluinos @ LHC • Long-Lived Gluinos in Cosmic Rays SUSY 05 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): m. S ~ 109 -12 Ge. V – Fermions protected by chiral symmetry • Phenomenological Successes: – – Retain gauge coupling unification Higgs mass predicted to be `heavier’: m. H ~ 120 -150 Ge. V Flavor & CP problems are automatically solved Proton decay is delayed (occurs via dimension-6 operator) • Collider signatures & Dark Matter implications substantially different!
This ties into the Landscape picture Courtesy of Linde
Fine-tuning does occur in nature 2001 solar eclipse as viewed from Africa
• 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) Split SUSY @ 1 -loop m. S = 109 Ge. V 1 Te. V MSSM @ 1 -loop Arkani-Hamed, Dimopoulos hep-ph/0405159
Higgs Mass Prediction: (See Dimopoulos) Higgs Mass @ 1 -loop tan = 50 1 Error bands reflect mt & s errors m. H = 130 -170 Ge. V for m. S > 106 Ge. V Arvanitaki, Davis, Graham, Wacker hep-ph/0406034 Measurement of gaugino Yukawas determines SUSY breaking scale
LSP ( 10) is still dark matter candidate Main annihilation channels: • No scalar exchange • depends on fewer parameters 1 0 h 1 0 f, V(*) 1 0 V(*) + co-annihilation graphs very efficient!! (See Dimopoulos) Points which satisfy WMAP relic abundance constraint Pierce, hep-ph/0406144
Collider Phenomenology: EW Gauginos • Produced in pairs via Drell-Yan • 10 is LSP • Only open decay channel: ( 20) 1 0 No cascade decays! W (Z) Tri-lepton signature sill valid, except Gaugino couplings (at the Te. V scale) are smaller than those in MSSM GUT tests require accurate coupling measurements @ ILC
Collider Phenomenology: Gluinos • • JLH, Lillie, Masip, Rizzo hep-ph/0408248 Pair produced via strong interactions as usual Gluinos are long-lived Gluinos as LSP: Baer etal 1998 No MET signature Interesting detector signatures q Gluino lifetime: 1 0 ~ ~ g q q ranges from ps to age of the universe for Te. V-scale gluinos (Cosmological constraints) • ~ 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 m < Prob -m > m
Energy Loss in the Detector • Hadronic Interactions: RN RX Interactions due to light constituents energy loss E ~ ~ k k typically ~ (0. 1 -0. 35 Ge. V) – model with constant differential or triple pomeron – deposits few 100 Me. V per interaction Mean interaction length: ~ 19 cm in Fe 100 Ge. V R with E = 400 Ge. V, deposits at most 6. 4 Ge. V in CDF • Ionization: Bethe-Bloch Eqn – sizeable energy loss for slow moving R-hadrons – fast moving R-hadron deposits ~ 1. 5 Ge. V Either case: amount of energy deposition may escape triggers!
Case 1: constant differential Case 2: triple pomeron Average speed of gluino @ Tevatron
Gluino Production: = 0. 2 mgluino as suggested by NLO
Searches: 1. Stable, neutral R-hadron: most challenging case! • Energy loss via hadronic ints unobservable • Consider Gluino pair + jet production • Trigger on high p. T jet • Since scalars decouple, use QQ + jet production Monojet Searches: CDF: LHC: One central jet ET > 80 Ge. V MET > 80 Ge. V Run I 284 events observed 274 16 expected New Physics < 62 events one central jet ET > 750 Ge. V MET > 750 Ge. V expect ~ 4200 bckgnd events Mgluino > 1. 1 Te. V for 100 fb-1 Mgluino > 170 Ge. V 215 Ge. V (scaled Run II with 1 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 Ge. V) to 0. 4 (m = 500 Ge. V) @ 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: LHC: Heavy charged stable Scale CDF results mgluino > 2. 4 Te. V Particle search yields mgluino > 270 Ge. V (Run I) 430 Ge. V (Run II with 2 fb-1) Ionization loss (d. E/dx) for ≤ 0. 85: Mgluino > 300 Ge. V (Run I)
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 Ice. Cube • p+N gluino pairs • R-hadrons form • interact with nucleons in atmosphere & ice • Showering R-hadrons very energetic! • Deposit ~ Te. V in atmosphere • Deposit ~ 40 Te. V in Ice. Cube
Number of events expected @ Ice. Cube Not competitive with colliders
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 m~ ~ 270 Ge. V g ~ – LHC search reach up to mg ~ 1 Te. V • Search reach extended if R-hadrons charged • Cosmic ray signals not quite competitive with colliders