Giuseppe Ruggiero - Meeting with SPSC referees 1

Preparation for the K+ Analysis

Giuseppe Ruggiero (CERN)Meeting with SPSC Referees

CERN, 02/04/2012

02/04/2012

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Question

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

02/04/2012

Gino Isidori private comunication

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LHC results and New Physics ScenariosExperimental results/assumptions:

Flavour structure in agreement with SM predictions (B-factories).

SUSY not observed directly at LHC up to now.

Higgs observed at LHC and MH = 125 GeV/c2 (assumption).

Theoretical assumption:New Physics has a Supersymmetric structure.

Theoretical consequences:SUSY MFV unlike.

SUSY high tan scenarios ruled out.

Most probable scenario “Natural SUSY”: heavy not light light (no significant constraint from direct SUSY searches at LHC up to now).

02/04/2012

u,d,c˜ ˜ ˜b̃t̃

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Possible Effects of New Physics Where to look for effects of New Physics:

Physics processes sensitive to effects.Reminder: the can contribute to SM level via loops only.Z-loop among the best places, complementary to direct search (couplings vs masses).

Physics processes:FCNC decays (theoretical clean): Bs , K .

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 , K (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 ?)

02/04/2012

t̃t̃

t̃t̃ †

t̃t̃ †

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Conclusions

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

Our direct competitors:LHCb: Bs at 10% precision

LHC @ 14 TeV: direct stop search.

02/04/2012

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Preparation for the K+ analysis

02/04/2012

Goals: Establish an analysis procedure for the K+ branchnig ratio measurement in order to be ready for the 2014 data taking.Provide a detailed review of the physics sensitivity of the experiment.

NA62 Physics overview

02/04/2012 7Giuseppe Ruggiero - Meeting with

SPSC referees

Separated from signal by kinematic cuts

Not separated by kinematic cuts

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Scheme of the K+ Analysis“Cut and count” analysis.

UPSTREAM DOWNSTREAM

EVENT

GTK / CEDAR Spectrometer / RICH / etc.

K Candidate + Candidate

Beam pile-up solution

Kinematics

02/04/2012

Tools for the analysis: Simulation of the beam line based on Turtle and on Geant4.Complete and detailed simulation of the NA62 detectors based on Geant4.

Main features:Kinematics (GTK, Straw Spectrometer)Veto (LAV, LKr, IRC-SAC, MUV3)Particle-ID (RICH, LKr, MUV)

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Kinematic Selection

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 m2

miss.

02/04/2012

Spectrometer reconstruction readyComplicate pattern recognition because of the geometry of one single chamber.Works properly also in multi-track environment (tested on K +).>99% efficiency for single track. >95% for 3-track events reconstruction.(P)/P = 0.32% 0.009% x P (GeV/c); () = 45 20 rad (depending on Ptrack).

GTK reconstruction ready.

1 view region 2 views region 3 views region 4 views region

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Kinematic Selection: Cuts on M2miss

R2R1

02/04/2012

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Channel M2miss cut Overall acceptance

+ 0.57 0.147

+0 (2.2 ± 0.5 ) x 10-4

(4.4 ± 1.0 ) x 10-5

+ (0.7 ± 0.1 ) x 10-4

(1.0 ± 0.1 ) x 10-5

++- (1.4 ± 0.2 ) x 10-4

(6.9 ± 2.0 ) x 10-702/04/2012

Acceptances after Kinematic Selection

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Beam Pileup and GTK reconstruction

All the possible GTK hit combinations considered.Real tracks: GTK hits from the same track (Pileup tracks, Kaon tracks).Fake tracks: GTK hits from different beam tracks.

Before selection cuts:Average reconstructed track per event: 27Fraction of: Kaons 3.6%, Pileup 5.3%, Fake 91%

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Real Track Recognition:Discriminant variable: global 2 Track recognition: global 2 < 20.After track recognition:

Average reconstructed track per event: 2.6Fraction of: Kaons 38% , Pileup 56%, Fake 6.1%.

Pileup simulation: T=2ns, Rate=750 MHzAverage tracks in GTK expected per event: 2.5 (1 K, 1.5 pileup)

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Beam Pileup and Kaon-ID Inputs for Kaon track identification: T = Ttrack – Tevent, CDA.

02/04/2012

T for all the tracks CDA for all the tracks

Results after Kaon - ID:Fraction of: Kaons 99.4%, Pileup 0.6%, Fake <0.1%

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Multi-Charged Particle Background

02/04/2012

Decay analyzed: ++-

Dangerous configuration: one + in the straw acceptance, the other + and the in the beam hole.

Countermeasure: the distance between MNP33 and chamber 4 allows up to 60 GeV/c to enter in the acceptance of the detectors downstream.

Possible flaws: decays and the is lost interacts hadronically.

Starting point:

Channel After Kinematic selection

Events/year

+ 0.147 56

++- (6.9 ± 2.0) x10-7 (1.9 ± 0.5) x 105

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Multi-Charged Particle Background

02/04/2012

RICH, CHOD, LAV11,12 multiplicity cuts: 5x102 rejection factor, 20% signal lossThe other in the IRC : rejection factor 2.Residual events: decays and the goes outside the acceptance of the downstream detectors

Solution: extensions of the CHOD:

80x80 cm2 box of scintillator arrays behind the RICH.

LAV12

CHOD

Residual events: interacting in the detector material before

reaching the downstream spectrometers.

Solution Segment reconstruction in straws;

Use of LAV 9, 10.

Straw 1

Straw 2

RICH entrance window

RICH exit window

Photons in the Small Angle Region

IRC SACPhotons: 247 140 47 042

Inefficiency 3.6 x 10-4 7.9 x 10-4

Inefficient photons 89 37

Photonuclear (mainly in RICH) 66

Conv. before STRAW3 11

Conv. in RICH 11

Conv. in IRC 1

Conv. in STRAW3 29

Conv. in STRAW4 5

Conv. in SAC 3

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Giuseppe Ruggiero - Meeting with SPSC referees

Evaluation of the effect of the material in the IRC and SAC acceptances on the photon rejection inefficiency (beam pipe).Effect studied using photons from +0 which passed the kinematic selection.

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Photons in the Forward Region

02/04/2012

Probability of interaction: 20%Most part of the interactions are simple photon conversions (e+e-

pairs detected as well in the LKr).

Probability of nuclear interaction: 10-3

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).

Energy < 1 GeV

1 – 5.5 GeV 5.5 – 7.5 GeV

7.5 – 10 GeV

>10 GeV

LKr Inefficiency 1 10-3 10-4 5x10-5 8x10-6

Effect of the material

- (2.1±0.5)x10-4

(1.4±0.5)x10-4

(5±2)x10-5 (3.7±1.6)x10-6

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

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Muon Suppression with Calorimeters: Analysis

02/04/2012

+ and+ generated with energy fixed at 20 and 30 GeV. Shower width used to discriminate between + and+ both in MUV1 and LKr.

Rejection factor from LKr+MUV1: 50 (@ 20 GeV).Rejection factor from MUV3: 104

Total muon rejection factor: > 105

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

This analysis is just started.

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Conclusions (2011)

02/04/2012

Several effects have been studied, or are under study:Kinematic rejection

Effect of the non gaussian tailsBeam pileup

Multi-charged particle backgroundUse of the veto detectorsSpot 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%.

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Plans for 2012

02/04/2012

Preparation to the K+ analysis will continue.Better definition of the multiplcity cuts.Effect of the material on the detection of the photons in the LAVs. Study of the possibility to measure the photon detection inefficiency using data (as it has been done for the LKr in 2007).Progress in the muon identification using the calorimeters.Determination of the expected level of background coming from:

K+ +0()K+

K+ ()K+ e+(+)Beam induced background

Accurate evaluation and optimization of the signal acceptance.