R-hadrons and Highly Ionising Particles: Searches and Prospects David Milstead Stockholm University The need for new particles Why they could be heavy and stable How can we identify them in current and future experiments
Where we Stand with the Standard Model The SM is the best theory we ve got (g-2)/2 electron = 1159652188.4(4.3)x10-12 (exp) (g-2)/2 electron = 1159652153.5(28)x10-12 (th.) + every result from LEP, HERA, Tevatron. But. It may be beginning to crack muon g-2
.It certainly is incomplete Naturalness and fine-tuning In the SM, the Higgs boson mass is tuned to the level of O(10^34) No candidate for dark matter Inexact unification of couplings and unification of only 2 forces.
One possible solution Supersymmetry - R p partner for every particle with the same mass and charge but differing with spin ½. SUSY particles with mass around TeV scale cancel quantum corrections up to arbitrarily large scales. No fine tuning of Higgs mass! Unification of couplings Dark Matter Candidate
Fundamentally SUSY is beautiful Phenomenologically it is expensive Many models and parameters (MSSM >100 parameters) Distinguish between fundamental properties of models stable particles Scenario Quasi-stable colour particles Split-SUSY gluino (R-hadron) octet GMSB SUSY 5D stau, stop (Rhadron) stop (R-hadron) colourless, singlet singlet Finding a stable massive charged particle may narrow the search. Identifying its colour is even better!
Split SUSY Abandon the Hierarchy Problem! Supersymmetry breaking occurs at high scale M s >>1000 TeV Scalars have masses at this scale Higgs light Fermions light
Some nice theoretical features of Split SUSY Long proton lifetime FCNC limits M s > 100 TeV EDM limit M s > 1000 TeV Unification of Coupling Dark matter candidate neutralino?
One nice experimental feature of Split SUSY Heavy squark, light gluino -> (meta)stable gluino
Implications of a stable gluino Hadronisation into bound states carrying R-parity -R-hadrons g + qq g + qqq g + g R-meson R-baryon gluino ball Many possible signatures, including flipped charge in nuclear interactions R + + n ->R - + p + π +
Are there relic R-hadrons around us? Present day abundance 1 σ annihilation Mass limits from searches of heavy exotic hadrons condensed in baryonic matter. Water Search for heavy hydrogen-like atoms in water (HRO) M>10 TeV Isotopes R- bind to nucleons -> heavy isotopes M>10 TeV Meteorites Heavy hadrons in iron meteorites excluded M>650 GeV
Searching for R-hadrons in a generic detector! muon chamber Calorimeter R + (1) Late arriving muon (2) flipped charge (1) E/p similar to muon (2) steps of hadronic energy deposition Tracking R - High ionisation energy loss
Particle Species Gluino R- hadrons Stop R-hadrons Allowed Hadronic Reactions (mesons) R + -> R 0, R 0 -> R +, R - -> R +, R - -> R 0, R 0 -> R - R + -> R - R + -> R 0, R 0 -> R + Antistop R- hadrons Staus R - -> R 0, R 0 -> R - none Only a gluino R-hadron can flip charge!
Need some models for guidance (1) Hadronisation of gluinos PYTHIA (string) - HERWIG (cluster) Open questions: q Neutral/charged fraction Mass spectrum (resonances) (2) Model for nuclear scattering σ(gluino-p) 1/M 2 Heavy gluinos are spectators Mesonic quarks interact! K.E. quarks =(γ 1)m qq GeV) Old particle physics regime!
!" # $ %&'( $ %))&)*& +%,* Energy Loss Kraan
Accelerator Searches for Stable Massive Particles HERA Masses up to 50 GeV Rp-violating only Tevatron pp Tevatron -!.,/ HERA ep LEP e+e-,lhc pp 012 34.,/ 05 # 36/ 0%
Prospects at the Tevatron pp-> gluino+gluino D0 390pb 1 Search for stable, highly ionising particles using muon timing M<100 GeV for stau 750fb -1 now available Expect at least 2fb -1 by 2007
Conversions of R-hadrons through D0 Calorimeter R+ R- R+ R0 R- S++ S+ S0 S- R+ R0 R- S++ S+ S0 S- 7 ( R0 R+ R0 R- S++ S+ S0 S- Mesons end up as baryons
Estimating stopping, neutral production and charge flipping. Consider D0 muon timing cut for β<0.95 Mass /GeV # expected stable highly ionising tracks # flippers # muon tracks with no earlier track link 100 200 300 1x10 5 2x10 3 140 4x10 4 7x10 2 400 4 1 1 Tevatron sensitive to gluino R-hadrons up to 300 GeV for 2fb -1. D0 muon charge reconstruction allows observation of flippers and identification of gluino-r-hadron. 50 5x10 4 8x10 2 60
605 # 8%9 pp collisions at 14 TeV from 2007! 265 Expect 5x10 5 for mass 300 GeV for one year s running
R-hadrons at ATLAS Simulated pp-gluino+gluino event
:1;2 60 +( Etmiss Et-tot Pt-muon Thrust Use these to make discovery up to 1 TeV But. variables are limited and not R-hadron specific
Flippers at ATLAS 7 ATLAS detector sensitive to flipped charge for pt above 1 GeV P T /GeV This signature alone can lead to discovery in first year of running for masses up to 1 TeV.
Flippers and µ µ,µ + µ + - Muon det Calorimeter Separating Gluinos, Stops and Staus No ID track and µ + µ - No flippers and µ + µ + Inner det + 0 + p p p p p p + 0 - - + - gluino-gluino stop-antistop < stau-antistau < gluino-gluino stop-antistop stau-antistau < gluino-gluino stop-antistop stau-antistau Nuclear Scattering Modified for Stop and Analysis under way.
Mass Reconstruction W. Kilian et al., hep-ph/0408088 Use time of flight information to reconstruct mass Expected ATLAS resolution Mass /GeV Clean method of reconstructing (N)LSP mass.
Decaying R-hadrons Secondary vertex R->jet + neutralino Or For τ> weeks µ chamber Calo R-hadrons stopped In the calorimeter can decay during off-beam time. O(100) GeV jets from nowhere.
R-hadrons at IceCube? J. Hewett et al., hep-ph/0408248 Cosmic rays with E>500 TeV can produce gluinos (mass 500 GeV) through nucleon interactions in the atmosphere. Expected number of events /per year <1 for masses above 170 GeV. R-hadrons lose between 60 and 300 GeV in the atmosphere Pair of R-hadrons separated by 100-150m through IceCube
Summary The discovery of new stable, massive charged particles and the quantification of their colour would be of fundamental significance. The absence of such particles is of fundamental significance in developing any theory beyond the SM. Discovery windows are being opened by the Tevatron and the LHC in the mass regions where we can expect new physics..