Preparation for the k p nn analysis
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Preparation for the K +  p + nn Analysis. Giuseppe Ruggiero (CERN) Meeting with SPSC Referees CERN, 02/04/2012. Question. Given the last LHC results on New Physics searches and on the Higgs, can the K  pnn BR measurement still be considered a “golden mode” for new physics discovery ?.

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Preparation for the k p nn analysis

Preparation for the K+p+nn Analysis

Giuseppe Ruggiero (CERN)

Meeting with SPSC Referees

CERN, 02/04/2012

Giuseppe Ruggiero - Meeting with SPSC referees


Question
Question

  • Given the last LHC results on New Physics searches and on the Higgs, can the Kpnn BR measurement still be considered a “golden mode” for new physics discovery ?

Gino Isidori private comunication

Giuseppe Ruggiero - Meeting with SPSC referees


Lhc results and new physics scenarios
LHC results and New Physics Scenarios

˜

b

˜ ˜ ˜

u,d,c

  • Experimentalresults/assumptions:

    • Flavourstructure in agreement with SM predictions(B-factories).

    • SUSY notobserveddirectly at LHC up tonow.

    • Higgsobserved at LHC and MH = 125 GeV/c2(assumption).

  • Theoreticalassumption:

    • New Physicshas a Supersymmetricstructure.

  • Theoreticalconsequences:

    • SUSY MFV unlike.

    • SUSY high tanbscenariosruled out.

    • Mostprobable scenario “Natural SUSY”:

      • heavy

      • not light

      • light (no significantconstraintfromdirect SUSY searches at LHC up tonow).

˜

t

Giuseppe Ruggiero - Meeting with SPSC referees


Possible effects of new physics
Possible Effects of New Physics

˜

˜

˜

˜

˜

t

t

t

t

t

˜

t

  • Whereto look foreffectsof New Physics:

    • Physicsprocesses sensitive toeffects.

    • Reminder: the can contributeto SM level via loopsonly.

    • Z-loopamong the best places, complementarytodirectsearch(couplings vs masses).

  • Physicsprocesses:

    • FCNC decays (theoreticalclean): Bs mm , K  pnn.

    • Direct production of

  • FCNC processes:

    • Sensitivity to non-MFV structures of the A-terms (LR mixing) of the up-squarks mass matrices.

    • Expected effects: 20-30% max, both on Bs mm , K  pnn(highly correlated).

    • <10% precision of the SM BR required for both the channels (LHC on Bs?)

  • Direct production:

    • via gluino (production via gluon has too small BR and too high irreducible background from concurrent tt production).

    • High energy required (LHC 14 TeV ?)

Giuseppe Ruggiero - Meeting with SPSC referees


Conclusions
Conclusions

  • The recent LHC results point towards a scenario where the Kpnn is one of the few places where new physics can give measurable effects (if new physics is SUSY…)

  • Our direct competitors:

    • LHCb: Bsmm at 10% precision

    • LHC @ 14 TeV: direct stop search.

Giuseppe Ruggiero - Meeting with SPSC referees


Preparation for the k p nn analysis1
Preparation for the K+p+nn analysis

  • Goals:

    • Establishananalysis procedure for the K+p+nnbranchnigratiomeasurement in ordertobereadyfor the 2014 data taking.

    • Provide a detailedreviewof the physicssensitivityof the experiment.

Giuseppe Ruggiero - Meeting with SPSC referees


Na62 physics overview
NA62 Physics overview

Separated from signal by kinematic cuts

Not separated by kinematic cuts

Giuseppe Ruggiero - Meeting with SPSC referees


Scheme of the k p nn analysis
Scheme of the K+p+nn Analysis

  • “Cut and count” analysis.

  • Mainfeatures:

    • Kinematics(GTK, StrawSpectrometer)

    • Veto (LAV, LKr, IRC-SAC, MUV3)

    • Particle-ID (RICH, LKr, MUV)

GTK / CEDAR

Spectrometer / RICH / etc.

Beam pile-up

solution

UPSTREAM

DOWNSTREAM

K Candidate

p+ Candidate

  • Toolsfor the analysis:

    • Simulationof the beamlinebased on Turtle and on Geant4.

    • Complete and detailedsimulationof the NA62 detectorsbased on Geant4.

Kinematics

EVENT

Giuseppe Ruggiero - Meeting with SPSC referees


Kinematic selection
Kinematic Selection

  • GTK reconstructionready.

  • Spectrometerreconstructionready

    • Complicate pattern recognitionbecauseof the geometryofone single chamber.

    • Works properlyalso in multi-trackenvironment (tested on K +p+p+p-).

    • >99% efficiencyfor single track. >95% for 3-track eventsreconstruction.

    • s(P)/P = 0.32%  0.009% x P (GeV/c); s(q) = 45  20 mrad (depending on Ptrack).

  • Kinematic selection:

    • 1 Track reconstructed in the Straw Spectrometer, 15 < Ptrack < 35 GeV/c.

    • CDA and Z reconstructed vertex (60 m fiducial region).

    • Cuts on m2miss.

1 view region

2 views region

3 views region

4 views region

Giuseppe Ruggiero - Meeting with SPSC referees


Kinematic selection cuts on m 2 miss
Kinematic Selection: Cuts on M2miss

p+nn

p+p0

R1

R2

m+ n

p+p+p-

Giuseppe Ruggiero - Meeting with SPSC referees


Acceptances after kinematic selection
Acceptances after Kinematic Selection

Giuseppe Ruggiero - Meeting with SPSC referees


Beam pileup and gtk reconstruction
Beam Pileup and GTK reconstruction

  • Pileupsimulation: DT=2ns, Rate=750 MHz

    • Averagetracks in GTK expected per event: 2.5 (1 K, 1.5 pileup)

  • All the possible GTK hit combinationsconsidered.

    • Realtracks: GTK hitsfrom the same track (Pileuptracks, Kaon tracks).

    • Faketracks: GTK hitsfromdifferent beam tracks.

  • Beforeselectioncuts:

    • Averagereconstructed track per event: 27

    • Fractionof: Kaons3.6%, Pileup 5.3%, Fake 91%

  • RealTrackRecognition:

  • Discriminantvariable: global c2

  • Trackrecognition: global c2 < 20.

  • After track recognition:

    • Averagereconstructed track per event: 2.6

    • Fractionof: Kaons 38% ,Pileup 56%, Fake 6.1%.

Giuseppe Ruggiero - Meeting with SPSC referees


Beam pileup and kaon id
Beam Pileup and Kaon-ID

DT for all the tracks

CDA for all the tracks

  • Inputs for Kaon track identification: DT = Ttrack – Tevent, CDA.

  • ResultsafterKaon - ID:

    • Fractionof: Kaons99.4%, Pileup0.6%, Fake<0.1%

Giuseppe Ruggiero - Meeting with SPSC referees


Multi charged particle background
Multi-Charged Particle Background

  • Decayanalyzed: p+p+p-

  • Dangerousconfiguration:

    • onep+ in the strawacceptance, the otherp+ and the p- in the beamhole.

  • Countermeasure:

    • the distancebetween MNP33 and chamber 4 allowsp- up to 60 GeV/c toenter in the acceptanceof the detectors downstream.

  • Possibleflaws:

    • p-decays and the m-islost

    • p-interactshadronically.

  • Startingpoint:

Giuseppe Ruggiero - Meeting with SPSC referees


Multi charged particle background1
Multi-Charged Particle Background

RICH, CHOD, LAV11,12 multiplicitycuts: 5x102rejectionfactor, 20% signal loss

The otherp+in the IRC : rejectionfactor2.

Residualevents: p-decays and the m-goesoutside the acceptanceof the downstream detectors

Solution:

extensionsof the CHOD: 80x80 cm2 box ofscintillatorarraysbehind the RICH.

LAV12

CHOD

Residualevents:

p-interacting in the detector material beforereaching the downstream spectrometers.

Solution

Segmentreconstruction in straws;

Useof LAV 9, 10.

RICH entrance window

Straw 1

RICH exit window

Straw 2

Giuseppe Ruggiero - Meeting with SPSC referees


Photons in the small angle region
Photons in the Small Angle Region

Evaluationof the effectof the material in the IRC and SAC acceptances on the photonrejectioninefficiency (beam pipe).

Effectstudiedusingphotonsfromp+p0whichpassed the pnnkinematicselection.

Giuseppe Ruggiero - Meeting with SPSC referees


Photons in the forward region
Photons in the Forward Region

  • Evaluate the effect of the material in front of the LKr on the photon rejection inefficiency (straw chambers and RICH).

  • Reminder: the LKr intrinsic inefficiency was evaluated on data (NA48 in 2007).

  • Probabilityofginteraction: 20%

    • Most part of the interactions are simplephotonconversions (e+e- pairsdetectedaswell in the LKr).

  • Probabilityofgnuclearinteraction:10-3

Multiplicitycuts in LAV9,10,11,12 and in the detectors downstream to the RICH applied.

Giuseppe Ruggiero - Meeting with SPSC referees


Muon suppression with calorimeters analysis
Muon Suppression with Calorimeters: Analysis

p+ andm+generatedwithenergyfixed at 20 and 30 GeV.

Showerwidthusedto discriminate betweenp+andm+both in MUV1 and LKr.

  • Rejectionfactorfrom LKr+MUV1:  50 (@ 20 GeV).

  • Rejectionfactorfrom MUV3:  104

  • Total muonrejectionfactor: > 105

  • p+efficiency: 90% (MUV1+LKr only).

    • Thisanalysisis just started.

Giuseppe Ruggiero - Meeting with SPSC referees


Conclusions 2011
Conclusions (2011)

  • Several effects have been studied, or are under study:

  • Kinematic rejection

    • Effect of the non gaussian tails

    • Beam pileup

  • Multi-charged particle background

    • Use of the veto detectors

    • Spot and cure possible flaws of the layout

  • Photon veto:

    • Effect of the detector material on the photon detection efficiency

  • Muon-ID using the calorimeters.

  • The most important backgrounds are under control.

  • Signal acceptance always about 10%.

Giuseppe Ruggiero - Meeting with SPSC referees


Plans for 2012
Plans for 2012

  • Preparationto the K+p+nnanalysiswill continue.

  • Betterdefinitionof the multiplcitycuts.

  • Effectof the material on the detection of the photons in the LAVs. Studyof the possibilitytomeasure the photon detection inefficiencyusing data (asithasbeendonefor the LKr in 2007).

  • Progress in the muonidentificationusing the calorimeters.

  • Determinationof the expectedlevelof background comingfrom:

    • K+ p+p0(g)

    • K+  p+p+p-

    • K+  m+n(g)

    • K+  p+p-e+(m+)n

    • Beaminduced background

  • Accurate evaluation and optimizationof the signalacceptance.

Giuseppe Ruggiero - Meeting with SPSC referees


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