Identification of the AC Leptons or double charged particles with the TRT.

1. Identification of the AC Leptons or double charged particles with the TRT. Oleg Bulekov, Anatoli Romaniouk MEPHI

2. Introduction: • Leptons of the Almost Commutative (AC) model. • Almost commutative geometry offers a specific way to unify general relativity, quantum mechanics • and gauge symmetries. • The AC-model of elementary particles, arising on this way, naturally embeds • the Standard model and predicts doubly charged AC-leptons, anion-like A−− and cathion-like C++, • which can bind in WIMP-like (AC)-atoms, being a nontrivial candidate for cosmological dark matter. • The model naturally involves a new U(1) gauge interaction, possessed only by the AC-leptons and providing a Coulomb-like attraction between them. This attraction stimulates the effective A − C recombination into AC-atoms inside dense matter bodies (stars and planets), resulting in a decrease of anomalous isotopes below the experimental upper limits. • AC-fermions are sterile relative to SU(2) electro-weak interaction, and do not contribute to the standard model parameters. • Being absolutely stable, primordial heavy AC-leptons should be present in modern matter. • M.Yu. Khlopov, C.A. Stephan, arXiv:astro-ph/0603187v2 20 Nov 2006

3. AC-Leptons Simulation. simulated as ’++ , ’-- with quantum numbers:L=2 M=500GeV Y=2 T=0 Q=2 500 GeV taken as an example but results presented below will not significantly change. • Hard process simulation, hadronization and showering with Pythia 6.403 • Detector simulation with GEANT4 (only multiple scattering and ionization are included) Simulation have been done in the framework of Athena 12.0.6, digitization, reconstruction and analysis –Athena 14.2.21. No ETHA constrains (Barrel + ECs) pp->AC++AC-- +X at √s=14 TeV 480 events have been produced BG Simulation: The 3000 single - with E=300 GeV have been produced using G4 single particle generator. (Athena 14.2.21 ) Detailed validation of the dE/dX information from the straws was done before all PID studies. 3

4. Signature of these events is very clear: ppAC++AC-- Heavy and rather slow particles but large fraction is close to a minimum ionization region Number of events Double charge gives a a specific signatures in all the detectors: Pixels, TRT, Calorimeters, Muon systems. We will concentrate on the TRT response to a single particle. Requirement of the presence of 2 particles of this sort significantly suppresses misidentification probability. truth

5. HL/LL vs momentum distribution for AC-Leptons. About 80% AC-Leptons are reconstructed as high Pt muons with momentum two times less than original particle momentum. The information about number of HL and LL hits has been taken from the MuidMuon Container. muons For AC-leptons in the minimum of ionization loses HL/LL is about 0.2: similar to that for muons above 200 GeV On the TRT event display this particles more often will look like muons with TR. How AC-leptons and Muons can be separated in the TRT? АС-leptons

6. What information we have in the TRT: • 1. Hits with HLT without HLT • 2. Hits with and without trailing • edge (without means last bit ON) • 3. Time information from each straw • What we can use as the parameters for the separation: • HLT hit fraction (only one definition Ntr/Nhits on track) • Mean trailing (leading) edge and its RMS • Mean time-over-threshold (ToT) and its RMS • The same for track-to-wire distance constrains (for instance <1.5 mm) • Different method of calculation of the values above. • Take into account ETHA (straw-track angle). • Information about TRT hits has been taken from TrkValidationNtuple on the step of reconstruction • If take everything -> quite many parameters and very often significantly correlated. But the correlation not always 100% and can be used as additional information. This definition is used in the current work 6 • Work is still in progress!

7. Mean Trailing Edge VS HL hit fraction • hits with + without HLT • with no constrains on the Tr Edge. AC-leptons Muons Although HL threshold helps but the largest separation comes from the signal shape analysis (trailing edge on this pictures and RMS) 7

8. Mean trailing edge VS RMS • hits with + without HLT • with no constrains on the Tr Edge. AC-leptons Muons Separation is good but still something needs to be done to minimize/eliminate overlap 8

9. Mean Trailing Edge VS HL hit fraction • hits with + without HLT • with 0 last bin for Tr Edge. At high luminosity trailing edge may not be measurable and hits with 0 last time bin may need to be used. 9

10. Mean Trailing Edge VS RMS • hits with + without HLT • with 0 last bin for the Tr Edge. Separation is very good we need larger statistics but what to do with the tails of the muon distribution.

11. Potentially separation can be improved using some constrains on the straw hits • Trailing edge distribution in the as a function of the wire to track distance for hits with 0 last bin. • Hits near the edge of the straw do not contribute to the separation. Can be excluded applying CUT for instance 1.5 mm

12. Mean Trailing Edge VS HL hit fraction • hits with + without HLT • with 0 last bin for Tr Edge. • Rtrack < 1.5 mm • Rtrack no constrains Generally separation of two classes of events is better 12

13. Mean Trailing Edge VS RMS • hits with + without HLT • with 0 last bin for the Tr Edge. • Rtrack no constrains • Rtrack < 1.5 mm Generally separation of two classes of events is better BUT some muons still there - issue of the tails of the distribution which is always the largest problem for the particle ID => more information is needed 13

14. ToT information • ToT VS track position in the straws • NO constrains on the last bin • Muons • AC-Leptons • Mean of the dToT=FIT-ToT on the track is used for the particle separation. • RMS of this value also brings a very important information. • In a reality fit parameters can be taken from • low momentum proton data.

15. Mean dToT and RMS • VS HL hit fraction • No constrains on the Tr Edge. Muons AC-leptons 15

16. Mean dToT vs RMS of dToT • no constrains on the Tr Edge. • Mean dToT vs RMS of TrEd • no constrains on the Tr Edge. Complimentary information about TrEd RMS may help indeed!

17. Mean dToT and RMS • VS HL hit fraction • With last bit 0

18. Mean dToT vs RMS of dToT • With lat bit 0. • Mean dToT vs RMS of TrEd • With last bit 0

19. Rtrack <1.5 mm • Mean dToT vs RMS of dToT • With lat bit 0. • Mean dToT vs RMS of TrEd • With last bit 0 • Again one can find that distance between two classes of events increased but some muon events are still in the AC-lepton area. • Too many HL hits for this muons? 19

20. Let’s apply CUT dToT<4 • Mean dToT vs RMS of TrEd • With last bit 0 • Mean dToT vs RMS of dToT • With lat bit 0. • One sees that significant fraction can be removed applying • RMS cuts BUT not everything

21. Let’s apply CUT dToT<4 • Mean dToT vs Mean HLT • With lat bit 0. • Mean TrEd vs RMS of TrEd • With last bit 0 • HLT information does not help in that case ether! • Mean Trailing edge CUT can help a bit but there 2 muons which look like double charged particles 21

22. To clean a bit more one can use hits with Rtrack<1.5mm Mean dToT<4 • But still 2 muons look like double charged particles! • Mean Trailing edge CUT shell help 22

23. Conclusions: • Double charged particles have very clear signature and the muon background can be highly suppressed using combination of the parameters of the signal from the straws. Even few simple cuts allow to achieve rejection factor of ~103 with a minimum loss of the signal. • RMS information for TrEd and dToT is very useful and improves separation • dToT and TrEd are certainly correlated but bring complimentary information which might be used for the muon background suppression. • Selecting straw only with Rtrack <1.5 mm improves separation. • Some special calculation methods of the TrEd and dToT and their RMS may improve identification properties of the TRT. A straw-track angular information will certainly improve the separation. • There are muon events (clearly 2 in this simulation) which looks as double charged particles • More detailed analysis of the events with a signature of the double charged particles is required. • We shell start using data to separate slow protons from pions and electrons applying this method after identification criteria are finalized.

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25. Validation of the dE/dX information Доля стро с энерговыделением выше заданного значения For calculation of energy deposition in the straw we summarize energy deposition from every cluster in the straw caused by particle of given type. Mean deposited energy in the minimum of ionization is 4 times more for AC- leptons than for pions