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Colored SUSY and R-hadron physics in the ATLAS detector

Colored SUSY and R-hadron physics in the ATLAS detector. QCHS-06. Rasmus Mackeprang, rasmack@nbi.dk. ~. t. Outline. SUSY reminders using SPS1a as an example Light scenario R-hadron phenomenology R-hadron measurements. 0. Â. 1. >. >. >. m. m. m. m. 0. ~. 0. ~. ~. ~. l.

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Colored SUSY and R-hadron physics in the ATLAS detector

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  1. Colored SUSY and R-hadron physics in the ATLAS detector QCHS-06 Rasmus Mackeprang, rasmack@nbi.dk

  2. ~ t Outline • SUSY reminders using SPS1a as an example • Light scenario • R-hadron phenomenology • R-hadron measurements

  3. 0 Â 1 > > > m m m m 0 ~ 0 ~ ~ ~ l q A G V 0 4 1 0 0 Â Â ¡ 2 1 m m e = = = 1 0 0 : 2 ¯ 1 0 0 t > a n ¹ = ; Basic SUSY phenomenology • Using SPS1a • Defined in mSUGRA using parameters: • SUSY spectrum has so we have the squark decaying through a neutralino and a slepton to the LSP which is stable and escapes the detector.

  4. ~ ¨ ¨ 0 0 § § l l l l ~ ~ ~ q  q q  q ! ! ! L 2 1 f R n e a r n e a r a r Snowmass paper ISAJET 7.58 Cascade decays • Sequential decay: 100 % 12.1 % ~32 %

  5. 0 Â 1 m m m m l l l l l l q q q ; ; ; 1 2 Kinematic variables • As the escapes the detector one may form these invariants: • Note that we don’t know ”near” from ”far” lepton  Maximize/minimize in combination choice.

  6. 2 2 2 2 ( ) ( ) ¡ ¡ m m m m 0 ~ ~ 0 ~ ~ l l   d 2 R R ( ) e g e 2 1 m = l l 2 m ~ l R 2 2 2 2 ( ) ( ) ¡ ¡ m m m m 0 0 0 ~ ~ ~ ~ q L    d 2 ( ) e g e 2 2 1 m = l l 2 q m 0 ~  2 2 2 2 2 ( ) ( ) ¡ ¡ m m m m 0 0 ~ ~ ~ ~ q l d L   2 e g e R ( ) 2 2 m = l i 2 q m n m 0 ~  2 2 2 2 2 ( ) ( ) ¡ ¡ m m m m 0 0 ~ ~ ~ ~ q l L   d 2 R ( ) e g e 2 1 m = l 2 q m a x m ~ l R Kinematic edges and masses Choose to minimize/maximize

  7. F l f f A j i i t t t t e a s o u r e s s a s y n g G V G V G V 1 5 0 1 0 0 5 0 > > > p e p e p e 1 2 3 t t t ; ; ; ; ; F M E G V 6 0 0 + + + + > ´ p p p p e f f i 1 2 3 4 t t t t t e m s s ; ; ; ; ; ( ) F E G V M 1 0 0 0 2 > m a x e f f i t m s s e ; : ; ( ) F l d l f h T i i t t t t w o s o a e e p o n s n o ¿ o o p p o s e c a r g e ( ) b ° h O S S F i t t u s a m e a v o u r w ( ) ( ) l d l G V G V 2 0 1 0 > > p e a n p e t t Production and analysis cuts • Events produced w PYTHIA 6.2 (100 fb-1) and run through a fast detector simulation • Analysis cuts:

  8. d l i t t t ( ) l l e g e n o m n a r e c s y s s a 7 7 0 7 7 7 7 0 2 4 0 0 8 0 0 5 § § m : v s : . : : : Lepton-lepton invariant mass • Before and after OS-OF lepton background subtraction: ATLAS Prelim. Nominal value OS-SF SUSY+SM OS-OF SM

  9. d l i t t t ( ) l l e g e n o m n a r e c s y s s a 4 3 1 1 4 3 1 3 4 3 2 4 § § m q : v s : . : : : qll-edge ATLAS Prelim.

  10. l l M M i i i t t t t t t ( ( ) ) l l a n x n n o o m m n n a a r r e e c c s s y y s s s s a a 3 3 0 8 2 0 1 3 3 3 0 7 0 9 8 4 3 3 0 8 1 1 5 8 § § § § m m q q : : v v s s : : . . : : : : : : ql ATLAS Prelim. ATLAS Prelim.

  11. h h i l i i 0 g ( ) ( ) l m a x m a x o w m n m n ~ ¡ m m m m m m m m  L 1 l l l l l l l l l b l ; ; ; ; ; ; ; q q q q 2 h " # t 0 0 ( ) ( ) ( ) e o r y e x p ( ) m a x ~ m a x ~ ~ ~ 0 9 9 E E ¡ £ ¡ m  m m g m  m 4 1 l l X j j ; ; : ; : : : ¿ ¿ 2  = e x p ¾ j j Mass measurements • Measure a number of parameters and constraints: • Minimize chisquare function:

  12. ¢ ¢ 4 8 4 8 m m ~ 0 ~ l . . Â R 1 ¢ ¢ 4 7 8 7 m m 0 ~ ~ q . . L Â 2 ¢ ¢ 7 5 8 0 m m ~ ~ b g . . 1 ¢ ¢ 1 1 8 7 9 m m ~ ~ b q . . R 2 ¢ ¢ 5 0 5 1 m m ~ 0 ~ l . . Â L 4 Atlas Performance Estimate • Perform 105 ”Atlas experiments” and study the RMS of the resulting distributions of parameters: All errors in GeV. L = 300 fb-1

  13. ~ t ~ t Light Analysis • Cosmological inspiration • Discard the demand for unification (no assumptions on SUSY breaking) • Require matter-antimatter asymmetry to be generated at EW scale (CPV + light ) • Fix MSSM parameters using cosmological observables.

  14. ( ) M S S M P G V t a r a m e e r s e : S U S Y S t p e c r u m : d l 1 2 1 0 0 0 0 t s n g e n s c a a r s ~ 1 3 7 . . . t 1 d l 3 1 0 0 0 t r g e n s e p o n s ~ . . 1 5 1 0 t 2 ( ) Q 1 5 0 0 m 3 ~ 9 4 8 g ~ ( ) 0 t m R ~ ~ 1 0 0 0 0 ~ ¹ e » ( ) b 1 0 0 0 ; m R 0 ~ 5 8 Â A 0 1 b e ¹ ¿ ; ; ; 0 ~ 1 1 2 i ¼ Â A 6 4 3 2 - e x p t 2 + 1 1 1 M 6 0 Â 1 1 h 1 1 6 M 1 2 0 2 i ¼ 4 0 0 ¹ e x p 2 ¯ 7 t a n ( ) M A 1 0 0 0 Benchmark Point • LHS-2 (Les Houches 2005)

  15. Basic Phenomenology • Missing transverse energy • Kinematics doesn’t match t / W production • Jets too soft • Invariant mass combinations don’t add up. (W’s are virtual) 2 jets 2 b-jets 1 lepton

  16. Basic Cuts • One isolated e/ with pt > 20 GeV • Et,miss > 20 GeV • 4 jets with pt > 25 GeV (2 with pt > 35 GeV) • 2 b-jets Efficiencies: Signal: 0.47 % tt: 3.3 % Wbbj: 3.1 % b/s ratio ~ 15  (but soft QCD is gone) • Fast simulation study on 1.8 fb-1

  17. Excluding Ws c Demanding m(jj)min<60 GeV removes a lot of W background  b/s ~ 10 ATLAS ATLAS Background Signal GeV GeV

  18. ATLAS ATLAS M(bl) 1.8 fb-1 M(bjj) 1.8 fb-1 GeV GeV After background subtraction Next step would be fitting masses but that is a somewhat longer story...

  19. R-hadrons • Scenarios with metastable squarks/gluinos • Coloured SUSY particle binds with quarks to form R-(parity-stable) hadrons. Hence the name... • Possible scenario is split-SUSY: • Abandon hierarchy problem • SUSY broken far above the TeV scale  heavy scalars, light Higgs and light fermions • Long lived gluino

  20. Physics model for R-hadrons Interactions of • Quark system interacts • Gluino is ”just” a reservoir of kinetic energy • Interactions are thought to be pomeron / reggeon mediated: Figure: A.C. Kraan

  21. Basic Phenomenology • R-hadrons can change charge in hadronic interactions. • R-mesons tend to acquire baryon number • Cross section ensures hadronic interactions in calorimeter. • A pure sample of R-hadrons can be selected basically by requiring opposite sign tracks in ID and muon system. • Simulation implemented in Geant3 and Geant4

  22. Energy loss per collision 300 GeV/c2 gluino in iron: ATLAS Prelim. Geant4

  23. Triggering 300 GeV/c2 gluino • Charged R-hadrons in muon system will pass the single- 6 GeV trigger at even very moderate kinetic energies. • β > 0.7 satisfies timing. Losses: 25 % @ 300 GeV/c2 60 % @ 1 TeV/c2 Additional O(50%) loss from hadronic interactions in muon system ATLAS Prelim. 1 TeV/c2 gluino

  24. Seeing is believing... • That’s QCD all right • One high-pt track • Nothing on the other side • Signal back-to-back in the muon system (10 GeV track cut)

  25. ¹ p T I D j j p T Charge Flipping Quantified • Split SUSY scenario: (2 fb-1) • for negative ID track. R-hadron does not ”remember” initial charge. ATLAS Prelim.

  26. L T T i ¡ = i 0 ¯ c f T D i i t t : r m e i f d T T i i i t t t t : m e r o m c r e a o n o e e c o n 0 . R-hadron Mass Measurement • Gluino does not decay  Mass measurement requires β-measurement. • Use drift time in muon chambers:

  27. ¯ p m c ° = β-measurement • Use β as an assumption in track fit. • Divide events into momentum intervals • Minimize chi-square as: • Use that to fit the mass. ATLAS Prelim.

  28. Fitted mass • Input gluino mass was 300 GeV/c2 Mass scale can be determined to O(5-10%) using simple and generic methods. ATLAS Prelim. Fits not always stable

  29. Summary • The Atlas detector is sensitive to a broad spectrum of SUSY phenomenologies • Statistics of one year of nominal running should suffice for many phenomenologies • Knowledge of SM background (and thus of QCD) of paramount importance • We have yet to find the elusive SUSY • But hope prevails

  30. Backup slides

  31. ATLAS layout

  32. Trigger & luminosity • Low luminosity: 1033 cm-2s-1 10 fb-1yr-1 • High luminosity: 1034 cm-2s-1 100 fb-1yr-1 Trigger rates: • Raw: 23 collisions / 25 ns (40 mHz) • LVL1: 75 kHz • HLT: ~100 Hz

  33. ~ ¨ ¨ 0 0 § § l l l l ~ ~ 0 0 0 ~ ¨ § l l X ~ ~ ~ ~ q  q q  q ! ! ! L q  q  q  q ! ! ! 2 1 f R L n e a r n e a r 2 1 1 a r Cascade decays • Sequential decay: • Branched: Large m0 excludes decay through slepton

  34. 2 2 2 2 ( ) ( ) ¡ ¡ m m m m 0 ~ ~ 0 ~ ~ l l   d 2 R R ( ) e g e 2 1 m = l l d d 2 p e g e e g e = m 2 ~ < < l m m m R l l l l l l 2 2 2 2 ( ) ( ) ¡ ¡ m m m m ~ ~ 0 0 0 ¼ ( ) ~ ~ ~ µ l f i q > L    d 2 n - r a m e ( ) l l e g e 2 2 1 2 m = l l 2 q m 0 ~  2 2 2 2 2 ( ) ( ) ¡ ¡ m m m m ~ 0 0 ~ ~ ~ q l d L   2 e g e R ( ) 2 2 m = l i 2 q m n m 0 ~  2 2 2 2 2 ( ) ( ) ¡ ¡ m m m m ~ 0 ~ 0 ~ ~ q l L   d 2 R ( ) e g e 2 1 m = l 2 q m a x m ~ l R h 2 2 2 2 2 2 2 t ( ) [ ( ) ( ) ( ) r e s + ¡ ¡ m m m m m m m = 0 0 ~ ~ 0 l l ~ ~ ~ ~ l l q q L    R R 2 2 1 q 2 2 2 2 2 2 2 4 2 ( ) ( ) ( ) 2 2 1 6 ¡ ¡ + + ¡ m m m m m m m m m 0 ~ 0 ~ ~ 0 0 ~ 0 ~ ~ ~ ~ ~ q l l l L      2 R R R 2 1 2 1 2 2 2 2 2 2 2 ( ) ( ) ] = ( ) 2 4 + ¡ ¡ m m m m m m m ~ ~ 0 0 0 0 ~ ~ ~ ~ ~ l l q L     R R 2 2 1 2 Edges and thresholds Choose to minimize/maximize

  35. d h l l T i i t t t t t t ( ( ) ) l l l l e g r e e s n o n m o m n a n a r e r c e c s y s s y s s s a a 4 2 3 0 1 3 1 0 4 2 3 0 1 4 3 6 4 2 3 0 2 2 4 8 § § § § m m q q : : v v s s : : . . : : : : : : qll Edge and threshold

  36. t t t s y s d l E N F i i s a t g e o m n a ¾ ¾ l E ¡ s c a e d ( ) l l e g e 7 7 0 7 7 7 7 0 2 4 0 0 8 0 0 5 m . . . . d ( ) l l e g e 4 3 1 1 4 3 1 3 4 3 2 4 m q . . . . d e g e ( ) l 3 0 2 1 3 0 0 8 3 0 1 5 m q i . . . . m n d ( ) l e g e 3 8 0 3 3 7 9 4 3 8 1 8 m q . . . . m a x h t ( ) l r e s 2 0 3 0 2 0 4 6 2 0 2 8 m q . . . . SPS1a • Four equations, four masses (in case of universal squark masses)

  37. Snowmass paper ISAJET 7.58 G V 5 4 3 0 m e = ~ d : L G V 5 3 7 2 m e = ~ u : L Squark masses @ SPS1A

  38. T V 1 [ ] G V G V > 1 2 0 1 7 0 m e 2 ~ ~ ~ m e e ~ t t t t R ; Stop Constraints (Strong 1st order phase transition at EW scale) • mostly righthanded (LEP) • (light Higgs limit)  will be produced at the LHC.

  39. ( ) b G V L S P i 6 0 1 0 5 < < m  e n o ; ( ) b G V L S P i ~ 6 0 ( ) ( ) < G V 2 5 t m  e n o ¡ < m m  e ; Dark Matter Constraints Yellow allowed, green favoured. (Neutralinos supply dark matter) Higgsino LSP LEP excuded

  40. Signal vs Background • Difference in shapes in s/b • Background shape and normalization crucial. t Signal Wbb

  41. R-hadrons • Fits a bit unstable  Need unbinned method

  42. R-hadrons • Estimate of mass scale error

  43. R-meson to baryon conversion • R0-mesons with 300 GeV gluino sent through iron • All mesons end up as baryons.

  44. Search Strategies • A number of quality cuts can be applied to the tracks used, and R-hadron likeness cuts imposed. • Sensitivities exceeding the 5  level to metastable gluinos up to 1 TeV in mass has been demonstrated.

  45. R-hadrons • Assuming flat xsec (12 mbarn per light quark) • Assume even weights • Using phase space function to ensure asymptotic limits for 2  2 vs. 2  3. • Using parameterised cascade treatment already in Geant4. Figure: A.C. Kraan

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