Interactions and Detection of R-Hadrons with the ATLAS Detector Aafke Christine Kraan University of Pennsylvania (In 2004 at Niels Bohr Institute, Denmark)

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Interactions and detection of R-hadrons with the ATLAS detector Aafke Christine Kraan University of Pennsylvania (in 2004 at Niels Bohr Institute, Denmark)

Aafke Kraan, September 2004, CERN – p.1/32 Overview

Supersymmetry and R-hadrons Interactions of R-hadrons in matter LHC and the ATLAS detector Single R-hadron signatures in ATLAS Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.2/32 2 6 sleptons + 2 6 squarks S=0 photino + Winos and Zino + gluino S=

Higgsino S=

Supersymmetry

SUPERSYMMETRY For every boson, there is a fermion For every fermion, there is a boson

6 leptons + 6 quarks S= ¡ ¢ ¤ photon + and £ + gluon S=1

Higgs S=0

Aafke Kraan, September 2004, CERN – p.3/32 Supersymmetry

SUPERSYMMETRY For every boson, there is a fermion For every fermion, there is a boson

6 leptons + 6 quarks S= ¡

2 6 sleptons + 2 6 squarks S=0 ¢ ¤ photon + and £ + gluon S=1

photino + Winos and Zino + gluino S= ¡ Higgs S=0

Higgsino S= ¡

Aafke Kraan, September 2004, CERN – p.3/32 Why supersymmetry?

We know that e.g. no electrons exist with spin=1, so why bother? Supersymmetry can be a broken symmetry, so that masses of supersymmetric particles are higher than SM particles. Supersymmetry solves the hierarchy problem by making a cancelling in the large mass value of the Higgs mass Supersymmetry can provide a dark matter candidate Uniﬁcation of the gauge couplings

Aafke Kraan, September 2004, CERN – p.4/32 What is supersymmetry?

Supersymmetry is a broken symmetry Many ways of SUSY breaking, e.g. Gravitational interactions Gauge interactions

And many particles... lots of free parameters! To reduce this, usually make GUT uniﬁcation assumption: ¡ £ ¤ § ¥ ¢ ¢ ¢ ¢ ¢ ¡ £ ¤ ¦ ¡ £ £ £ £ ¨ ¨ ¨ ¡ £ ¤

Conventional SUSY models predict: Heavy gluinos LSP neutralino, sneutrino or gravitino: non-interacting!

Aafke Kraan, September 2004, CERN – p.5/32 Supersymmetry and R-hadrons

However, models exist, which predict stable gluinos!

String-models (Gunion, Chen e.a.) LSP gluino

GMSB models (Raby, Maﬁ e.a.) LSP or NSLP gluino Split supersymmetry (Dimopoulos+Arkani-Hamed)

Giudice+Romanino Abandon hierarchy problem Keep uniﬁcation of gauge couplings at GUT scale Low energy SUSY unnecessary (but light Higgs + fermions)

Scalars are heavy ¡ heavy squarks suppress gluino decay!

N.B. 1 Stable gluino phenomenology studied by: Hewett et al, Kilian et al...

N.B. 2 This work was started before the appearance of the split susy papers!!

Aafke Kraan, September 2004, CERN – p.6/32 Supersymmetry and R-hadrons

R-parity conserved, stable hadroniz¨ es to R−hadrons ¡

£ £ ¨¢ ¢¥¤ ¢ ¢ R-mesons: ¢ ¡

¢ ¢ ¢ ¨ ¢ ¢ ¢ R-baryons: ¢ , Hadronization ¡

¨ ¨ R-gluinoballs: ¢ (T. Sjöstrand): 22% mesons

R-hadron production at LHC: Gluino 22% mesons

¥ © ¦ ¦ ¨ ¨ § ¨ ( ¤ ) 44% mesons

¥ © ¥ ¦ ¦ ¢ ¨ ¨ ¢ ¨ § ¨ © ( ¤ ¤ ) 10% gluinoballs

¦ ¦ ¢ ¢ ¨ ¢ ¢ ¨ ¥© ¥ § ¨ © ( ¤ ¤ ) 2% -baryons

NB: heavy hadrons also predicted in theories with leptoquarks, extra dimenstions, GUT...

Aafke Kraan, September 2004, CERN – p.7/32 Search motivations Status 2001: bounds on stable gluinos from Searches in ordinary matter Cosmology (dark matter searches) However, limits widely spread and can be evaded! Good overview in M. Perl et al., Int.J.Mod.Phys.A16,2137,2001 Accelerator searches: Charged heavy particle searches Gluino LSP searches However, these limits are model (SUSY, hadr., nucl.scat.) dependent, charge dependent, limited to ¡ , no full simulation of hadr. interactions, etc. For details see PDG Conclusion: stable gluino not excluded!

Aafke Kraan, September 2004, CERN – p.8/32 Supersymmetry and R-hadrons

No standard SUSY parameterspace points available

¡ ¨ ¨ ¨ ¨ § ¨ ¨ © concentrate on ( ¤ ) Some distributions at event generator (PYTHIA) level:

3000 6000 2 2 M=300 GeV/c 2 10000 M=300 GeV/c M=300 GeV/c 2 2500 2 M=1500 GeV/c 2 5000 M=1500 GeV/c # events # events M=1500 GeV/c # events 8000 2000 4000

6000 1500 3000

4000 1000 2000

500 2000 1000

0 0 0 0 0.2 0.4 0.6 0.8 1 0 500 1000 1500 2000 0 200 400 β R-hadron R1 R2 2 R1 R2 2 pT sqrt((p x +p x ) +(p y +p y ) ) ¢ ¤ First look: £

Large ¦¦¥ R-hadrons balanced in xy-plane

Aafke Kraan, September 2004, CERN – p.9/32 Overview

Supersymmetry and R-hadrons Interactions of R-hadrons in matter LHC and the ATLAS detector Single R-hadron signatures in ATLAS Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.10/32 Interactions of heavy hadrons Electromagnetic interactions (charged hadrons):

10 8 )

2 6 Ionization losses: H 2 liquid m

c 5 1 − g

4 V

e He gas

large for heavy (slow) particle. M

( 3

d C

/ Al

E Fe

d 2 Sn − Pb

Bethe-Bloch formula 1 0.1 1.0 10 100 1000 10 000 βγ = p/M c

0.1 1.0 10 100 1000 M uon momentum (GeV/c)

0.1 1.0 10 100 1000 Pion momentum (GeV/c)

0.1 1.0 10 100 1000 10 000 Proton momentum (GeV/c)

¤ Multiple Coulomb scattering: § ¢

¡ £¦¥

£ ¤ £ ¤ ¢ §©¨

small for heavy particle: ¦ ¢ small but large ¦ !

Conclusion: – Electromagnetic interactions understood – Everything taken care of by GEANT

Aafke Kraan, September 2004, CERN – p.11/32 Interactions of heavy hadrons

Nuclear interactions (charged and neutral hadrons): (Some descriptions exist (Gunion et al, Raby et al,..), but not in GEANT...)

Below: simple model developed (with help of T.Sjöstrand) ¡£¢ ¡ ¡£¥ ¡£¦ ¤ R-hadron = passive gluino + interacting cloud. ¨ § reservoir of kinetic energy! © ¨ Example: with M=100, E=150 GeV ! & $# % ¨

" 0.7, so 1 GeV low!

To predict energy losses, we need to know: ¡*) ' +, /1032 ( ! " ".- " Int. length 4 4 per interaction

65 ¡ – of interaction – ! of scattered nucleon – Identity of scat. particles – Amount of new particles – Phasespace – Nuclear effects

Aafke Kraan, September 2004, CERN – p.12/32 An example: -p scattering

Low energy:

) 10 b m ( Reggeons+resonances n o i t

c + e

s π p ⇓ total s u u s o r u u C p p p d d 10

+ π p e lastic ++ uuu= ∆

-1 2 u u 10 1 10 10 πp 1.2 2 3 4 5 6 7 8 910 20 30 40 π π π d d πd 2.2 3 4 5 6 7 8 9 10 20 30 40 50 60 Center of mass energy (GeV)

d π

⇓ total

) b m (

⇓

High energy: Pomerons n o i t – c

e π p

s total

u s s o r

u C p p 10 d – π p e lastic Pomeron

-1 2 u 10 1 10 10

π π Laboratory beam momentum (GeV/c) d Processes: Elastic scattering Charge exchange Inelastic scattering

Aafke Kraan, September 2004, CERN – p.13/32 Nuclear scattering of R-hadrons

What happens if we attach a gluino to the pion?? Color-state of hadron-cloud changed: color octet! Mass splitting between hadrons with same quark content but different spin is slighty inﬂuenced Effect is small Resonance formation is inﬂuenced. Little information ¨ smeared out picture No changes in interactions; heavy gluino is spectator

d d u u p u p u u p u d p u p d u

~ ++ Pomeron Reggeon guuu= R d u u u u d d R R d R g R g R g ~ g~ ~ ~

Aafke Kraan, September 2004, CERN – p.14/32 Nuclear scattering of R-hadrons

What cross sections?

Many different R-hadrons different cross sections! Assume only and quarks

£ Dependence of ¡¢ unknown Assume constant geometrical cross section Thus, proposed total cross sections: ¤ ¤ ) )

§ ¥ ¥ ¥ – : from -p data: ¦ 4 mbarn, ¦ 20 mbarn ¨ ¤ ¤ ¤ ) ) ©

– : three active quarks now so = ¥

Aafke Kraan, September 2004, CERN – p.15/32 Nuclear scattering of R-hadrons

12 What processes? M = 1 GeV R

10 MR = 50 GeV Q-value M = 100 GeV

¢ ¢ R ¡ ¡

¡ ¡ 8 MR = 300 GeV

£ 6 ¥ ¥¨§ ¢ ¥ ¦ ¦ ¤ ¤

2 ©

Small : only ¨ and ¨ 0 0 100 200 300 400 500 600 700 Plab Processes:

¨ Elastic scattering: .

¨ Inelastic scattering: .

¨ Charge exchange: .

¨ Baryon exchange(!): (kinemat. favoured!!)

Ca 140 processes ¨ same rel. couplings (no CG coeff...)

¨ ¨ scattering? Construct phasespace funct. ( )

Aafke Kraan, September 2004, CERN – p.16/32 Energy losses per interaction 65

! of scattered nucleon: small ( 0.5

GeV) 3

Binding energy nucleon-nucleus: small 2.5 Iron

( 10 MeV) 2 /collision (GeV) > 1.5

Energy used for production of extra loss E < particles: small ( 0.5 GeV) 1 Other nuclear effects (Fermi motion, ex- 0.5 citation energy, evaporation energy, ...): 0 0 200 400 600 800 small ( 0.5 GeV) Kinetic energy (GeV) Conclusion: simpel platform for modelling cross sections and energylosses ready: – applicable to any kind of heavy hadron – implemented in GEANT 3 For details see: A.C.Kraan, Eur.Phys.J.C37:91-104, 2004

Aafke Kraan, September 2004, CERN – p.17/32 Overview

Supersymmetry and R-hadrons Interactions of R-hadrons in matter The LHC accelerator and the ATLAS detector Single R-hadron signatures in ATLAS (Full simulation) Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.18/32 The LHC accelerator LHC: 2007

Aafke Kraan, September 2004, CERN – p.19/32 The ATLAS detector ¡£¢¥¤

Muon RPC3 10 m ¡ ¨ chambers RPC2 7.5 m § ( 2 4 ¢ ¦ ) 18 cm

7 m ¡£¢©¤

§ 2 ¡

RPC1 ¨ 5 m 4 m ( ) 12 cm

++ + ¨ S n S p § 2 4 ¢ ¦ Tiles § ( ) 90 cm + + +

§ 2 ¡ Hadronic Tiles S p S n ¨ + + § ( ) 60 cm calorimeter S p S p 3 m Tiles o + o S p S n π LiAr Electro− S on Son 25 In ATLAS Calorimeters magnetic LiAr o interactions

R p S n 2 m N calorimeter 20 LiAr o + R p R p π 15 + Presampler R n Rop Magnet 10 1 m 5 TRT Tracking 0 0 1 2 3 4 5 Si strips η Pixels 0 m

Aafke Kraan, September 2004, CERN – p.20/32 Overview

Aafke Kraan, September 2004, CERN – p.21/32 R-hadrons in the inner detector Heavy particles are produced with high momentum ¢ ¤ ¡£¢ ¥ £ Heavy particles may be slow ( ¨ ) § heavily ionize § can mimic TR!

35 η=(0,0.5) γ 30 e Nr of TR hits 25 γ 20 15

0 ¦ -1 2 3 4 5 10 1 10 10 10 10 10 HT hits studied for TRT: βγ ¢¨§ ¢ ¤ ¡£¢ Only useful if 1 .

Heavy particles have large Time-over-threshold § Initial study shows some separation but TRT electronic changes may worsen this...

Aafke Kraan, September 2004, CERN – p.22/32 Detection of R-hadrons: calorimeters

How much energy is deposited?

80 2 90 M=300 GeV/c P=100 GeV/c 70 80 measured Muon

E P =200 GeV/c 2 60 T 70 R-hadron M=300 GeV/c R-hadron M=20 GeV/c2

Nr of events 60 50 Pion 50 Electron 40 40 30 30 20 20

10 10 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 η2.5 Emeasured/pmeasured ¦ ¥

Where is energy deposited? Constant energy deposit, or stopped on the way.

Aafke Kraan, September 2004, CERN – p.23/32 Detection of R-hadrons: muon system

Muon chambers can be used as TOF detector ( ¢ ) (idea from ATLAS-MU-006, for weakly interacting particles) ¡ However, track recon. assumes ¢ ... Misaligned tracks. £ £ ¢ ¢ ¡ ¢ Bad if ¢ , but good if ¢ ! ∆ t D t D

1 end

26 β β R-hadrons, start=0.7 0.9 η 2 =0.1 0.8 M = 300 GeV/c 24 0.7 0.6 22 0.5 of reconstructed Moore track ¢ 2

χ 0.4 20 0.3 Accuracy in :

18 0.2 £ £ ¤ ¢ ¢ ¤ ¡£¢ ¡¤

σ ¨ 2 0.1 §

16 0 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 β assumed in Moore reconstruction β start Internal time resolution of chambers could also be used

Aafke Kraan, September 2004, CERN – p.24/32 Overview

Supersymmetry and R-hadrons Search motivations Interactions of R-hadrons in matter Single R-hadron signatures in ATLAS (Full simulation) Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.25/32 R-hadrons triggers RPC’s at r=6.8, 7.5 and 10 m (barrel)

Muon trigger TGC’s at z=12.9, 14, 14.5 m (endcap) If charged R-hadrons reach trigger stations... R-hadrons ﬁre if within temporal gate time (18 ns) R-hadron must reach last trigger station in time (i.e.recorded in right ¦¨§ % ¡ ¡¤£ ¢ ¥

bunch crossing!) if arrival +25 ns : Complications with using the muon trigger:

signal delayed! OK if

time

, , jet trigger : combination crucial!

miss miss Note difference balanced (small ) and unbalanced events (large )!

Aafke Kraan, September 2004, CERN – p.26/32 Overview

Supersymmetry and R-hadrons Search motivations Interactions of R-hadrons in matter Single R-hadron signatures in ATLAS (Full simulation) Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.27/32 Event simulation ¡ ¡ ¡ ¡ ¤ ¤

Fast, but no TRT, muonchambers, E/p ¨ only topology and kinematics Use full simulation studies for R-hadron parameterization. ¥ ¥ ¢¤£ ¨ ¡ /§¦ / ¥ 4 Event selection variables: ¤ miss, , TOF Pseudo trigger simulation made: First level: ROI in calorimeters+muon system High level: event building (combined ID+calorimeters+muons) Background: events with high energetic muons: £ © b , t £ , W, Z, WW/WZ/ZZ

Aafke Kraan, September 2004, CERN – p.28/32

Some distributions (after trigger, 1 fb )

10 9 QCD 10 9 QCD 10 8 bbbar 10 8 bbbar 10 7 W,Z,diboson 10 7 W,Z,diboson Nr events Nr events 10 6 ttbar 10 6 ttbar 10 5 10 5 10 4 10 4 10 3 10 3 2 2 Cuts M=300 GeV 10 10 ¢ ¤£ ¡ / 10 10 1 1 100 GeV -1 -1 ¥ 10 10 ¥§¦

-2 -2 ¦ 10 10 £ -3 -3 135 GeV 10 10 ¡ ¨ / 0 250 500 750 1000 1250 1500 0 250 500 750 1000 1250 1500 ETmiss (GeV) pTµ (GeV/c) £ 250 GeV

80000 80000 70000 2 70000 2 60000 M=300 GeV/c 60000 M=300 GeV/c 50000 50000 40000 40000 Nr events 30000 Nr events 30000 Cuts M=900 GeV ¢ ¤£ ¡ 20000 20000 / 10000 10000 0 0 250 GeV 0 250 500 750 1000 1250 1500 250 500 750 1000 1250 1500 ¥ ¥§¦

40 50 ¦

2 35 2 £ 40 M=900 GeV/c 30 M=900 GeV/c 280 GeV ¡ ¨ 25 /

30 20 £ Nr events 20 Nr events 15 600 GeV 10 10 5 0 0 0 250 500 750 1000 1250 1500 250 500 750 1000 1250 1500 ETmiss (GeV) pT(R-hadron 1) (GeV/c) Aafke Kraan, September 2004, CERN – p.29/32 Discovery potential

Recall that lots of R-hadrons produced! £ ¡ £ ¤ ¡ ¤ ¡ ¤

¡ ¨ ¨ ¨ ¨ § M=100 GeV/ ¨ fb!! /yr LL £ ¢ £ £ ¤ ¡ ¤ ¡ ¤ §

¡ ¨ ¨ ¨ ¨ § M=300 GeV/ ¨ fb! /yr LL £ £ ¤ ¤ ¡ ¤

¡ ¨ ¨ ¨ ¨ § M=1700 GeV/ ¨ fb /yr LL

¤ ¥ ¥ Usual criterium: P= .

Using just standard event building information § ¥ £ ¢ ¡ ¥§¦ ¦ / ¡ / §

£ Simple cuts on miss, £ , 30 pb (3 years LL): discovery up to M=1400 GeV

Using more involved muon information like TOF: § ¥ ¥§¦ ¨ ¡

¨ Cut on £ and TOF 3ns up to 1700 GeV

/ High mass reach even further improved if using ¦ ! ATLAS excellent for R-hadrons thanks to muon system!

N.B. low masses discovery after a few days running!

Aafke Kraan, September 2004, CERN – p.30/32 Overview

Supersymmetry and R-hadrons Search motivations Interactions of R-hadrons in matter Single R-hadron signatures in ATLAS (Full simulation) Trigger issues Discovery potential Conclusion

Aafke Kraan, September 2004, CERN – p.31/32 Conclusion Heavy hadrons predicted in several models. Model developed to describe nuclear interactions and implemented in GEANT3 (Kraan, EPJC37:91-104, 2004). Fast simulation framework for heavy hadrons available. ¢ ¡£¢ ¥ Trigger issues are complicated but ok if . Characteristic signals in inner detector, calorimeters and muon chambers. If R-hadrons exist with mass below 1.7 TeV, they will be discovered at LHC. To appear: – proceedings Moriond QCD 2005 (in 2 weeks!) – ATLAS paper (wait for internal referees now)

Information: http://www.nbi.dk/ ¨ ackraan

Thanks to: Jørgen Beck Hansen, PavelAafkNee Kraan,vskiSeptember 2004, CERN – p.32/32