Measurement of Charged Pion Production by Low-Energy Protons: CERN Study, Slides of Nuclear Physics

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Measurement of the Production ofCharged Pions by Low-Energy Protons

Silvia Borghi^ Silvia Borghi

CERN^ -^ CERN-

UniversitUniversit

é^ de^ GèneveédeGèneve

On Behalf of the HARP Collaboration

NuFact06, 24-30 August 2006

Silvia Borghi^

HARP

Systematic study of hadrons produced by incident p and

±^ πwith p^ beam

between

1.5 and 15 GeV/c, more than 420 M pot•^ Large range of target materials,from H to Lead of different length;•^ Also measurements on specific targetsof existing

υ^ beams: K2K and MiniBooNE

Target^ Target lengthmaterial(λ%)

Beam^ #eventsMomentum(millions)(GeV) Solid targets^ K2K^ Al^

+12.9^ 15. Cu^ Cu “button”

+12.9, +15^ 1. Cu “skew”^ Cu^

2 +^

5, 50, 100,replica MiniBooNE^ Be^

+8.9^ 22. Cryogenictargets^ H^1 H^2 Water

18 cm^ ± 3,^ ± 8,^ ± 14.

Be^2 C (^2001 )^ Al Cu^5 Sn Ta^100 Pb

±^3 ±^^5 ±^^8 ±^^12 233.16 ±^^15 Negativeonly 2%and 5% N^70 8 D^1 H^0 10, 100^2

±^3 ±^^5 6 cm ±^^8 58.43 ±^^12 ±^^15 +1.5,9.6+8(10%)^

1.^ Inputs for the neutrino fluxcalculation for

K2K (^ υ^ ) andμ^ MiniBooNE (

υ^ ,υ)μe^

2. Inputs for precise calculation ofatmospheric

υ^ fluxes

3.^ π^ yield for the design of protondriver and target system ofNeutrino Factories and Superbeams4. Input for Monte Carlo generators

Main goals

Silvia Borghi^

Harp Acceptance

¾^ Large Angle Spectrometer:^ ƒ^ 0.35 rad <

θ^ < 2.15 rad

ƒ^ 100 MeV/c < p < 700 MeV/c ¾ Forward Spectrometer: ƒ^ 30 mrad <

θ^ < 210 mrad. ƒ^ 750 MeV/c < p < 6.5 GeV/c

Silvia Borghi^

5

TPC: Time Projection Chamber

• Equalization of pads • Evaluation of the drift velocity • Time calibration • Cross talk effect in the padplan

e

2.150 rad0.350 rad

Radius40 cm Magnet Targetposition^ Drift length 1541 mm

Rpc barrel Tpc drift volume Some problems needed corrections,e.g.: • Correction of static distortion due to a misalignment of the voltage betweenthe endcap of the inner field cage and the outer field cage^ • Detection of dynamic distortions, due to probably the charging of the chamberduring the spill. Applying a cut in the event in spill the data are not affectedand no correction is needed.

Silvia Borghi^

TPC performance

600MeV/c 300Mev/c

100mrad200mrad

Elastic scatteringH target (60 and 80 mm)and proton (pion) beam at3, 5, 8 GeV/c.•Momentum resolution•Angular resolution•Efficiency evaluation

Efficiency 91% ± 1%

Data 93% Monte Carlo

Cosmic ray data• Angular resolution• Vertex resolution• Momentum resolution

Silvia Borghi^

Calculation of differential cross section of

1^ number of protons on target N^ pot A Number of target nuclei and target thickness N^ ρ tA^ Number of particles observed as

α ’ type in bins of

reconstructed (p

, θ ), N(E) refers to data without targeti’ j’^

1 N^ pot (correction for primary proton interactions out of target)

A N^ ρ tA

Negligible-5<^

Correction matrix, i.e. unfolding of true ij

α^ variables from

reconstructed i’j’

α ’ reconstructed efficiency, acceptance, absorption, pion decay, tertiary production, PID efficiencyand contamination…Unfold detector resolution (I=true, j=rec)

NuFact06, 24-30 August 2006

Silvia Borghi^ Event selection

Target radius =15 mm

• trigger signal for only one beam particle:• hitting the target• reconstructed as protons byTOF and Beam Cherenkov• Signal of interaction trigger (ITC)• Selection of the first part of the spill

Pions

Protons

Pions Protons

Silvia Borghi^

Selection of data

Selection of the tracks 1.^ in large angle region: 0.350 rad <

θ^ < 2.150 rad

2.^ No error flag in the fit procedure 3.^ Minimum number of points 12 4.^ Reconstructed vertex in the target within theresolution:

|d^ ’ |< 8.5 mm^0

-7.2 mm +Z

min^ ≤^ ztarget

’• | cos(λ) | 0

≤^ 7.2 mm +Z

max^ target

Silvia Borghi^ Correction matrix, i.e. unfolding of true ijα^ variables from reconstructed i’j’

α’

Particle identification component Energy loss correction Efficiency can be factorized in: Momentum smearing correction

Silvia Borghi^

PID using only TPC

Silvia Borghi^

Electron and positrons contamination^ Electron and positron produced by^0 πdecay in

γ^ converting in e

±^ and by^ δ^ rays. Electrons and positrons by

δ^ rays are negligible Good separation for momenta lessthan 125 MeV/c Evaluation using the Monte Carlosimulation of

(^0) πwith similar momentum spectrum as themeasured for

± π. The normalization is done using thebins at low momenta

Silvia Borghi^

Correction matrix, i.e. unfoldin

g^ of

true ijα

variables from reconstructed i’j’

α’

Particle identification component Energy loss correction Efficiency can be factorized in: Momentum smearing correction

Silvia Borghi^ Correction matrix, i.e. unfoldin

g^ of

true ijα

variables from reconstructed i’j’

α’

Particle identification component Energy loss correction Efficiency can be factorized in: Momentum smearing correction

Silvia Borghi^ Efficiency correction Efficiency calculation using Montecarlo data:^ • Selection single particle events^ • How many events/particle are reconstructed To cross check with one found by elasticscattering Evaluation in angular and momentum bins(correction in angular and momentum bins)