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Mariyan BogomilovMariyan BogomilovCERN, CERN,

(Switzerland)(Switzerland)

University of Sofia and INRNE,University of Sofia and INRNE,(Bulgaria)(Bulgaria)

GAS@BS, Kiten, Bulgaria , Kiten, Bulgaria

THE HARP EXPERIMENTTHE HARP EXPERIMENT

On behalf of the HARP Collaboration

13-20 June 2005 13-20 June 2005

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Motivation for Motivation for HAHAddRRon on PProduction roduction experimentexperiment

Pion/kaon yield for the design of the proton driver and target systems of neutrino factories neutrino factories

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Maximizing +(-) production yield as a function ofTarget materialProton energy GeometryCollection efficiency

Poor experimental knowledge:Few material testedLarge errors (small acceptance)

Different simulations show large discrepancies for production distribution, both in shape and normalization.

factory designfactory design

need to measure yield and +/- ratio better than 5% need differential distributions (PL,PT)

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Motivation for Motivation for HAHAddRRon on PProduction roduction experimentexperiment

Pion/kaon yield for the design of the proton driver and target systems of neutrino factories neutrino factories

Input for prediction of neutrino fluxes for the MiniBooNEMiniBooNE and K2KK2K experiments

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Analysis for K2K: motivationsAnalysis for K2K: motivations

MC only

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K2K interestsK2K interests

pions producing neutrinos pions producing neutrinos in the oscillation peakin the oscillation peak

GeVE 75.05.0

mrad

GeVP

250

1

K2KK2K

interestinterest

K2K

far

/nea

r ra

tio

K2K

far

/nea

r ra

tio

Beam MC Beam MC,confirmed by Pion Monitor

To be measured To be measured by HARPby HARP

0.5 1.0 1.5 2.0 2.50 E(GeV)

oscillationoscillationpeakpeak

One of the largest K2K One of the largest K2K systematic errorssystematic errors

on the neutrino on the neutrino oscillation parametersoscillation parameters

comes from comes from

the uncertainty on the the uncertainty on the far/near ratiofar/near ratio

beam 250km

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Motivation for Motivation for HAHAddRRon on PProduction roduction experimentexperiment

Pion/kaon yield for the design of the proton driver and target systems of neutrino factories neutrino factories

Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments

Input for precise calculation of the atmospheric neutrino flux (from yields of secondary p,K)

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Atmospheric Atmospheric flux flux

Primary flux is now considered to be known better than 10%

Most of uncertainty comes from the lack of data to construct and calibrate a reliable hadron interaction model

Model-dependent extrapolations from the limited set of data lead to about 30% uncertainty in atmospheric fluxes

Need measurements on cryogenic targets (N2, 02) covering the full kinetic range in a single experiment

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Motivation for Motivation for HAHAddRRon on PProduction roduction experimentexperiment

Pion/kaon yield for the design of the proton driver and target systems of neutrino factoriesneutrino factories

Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments

Input for precise calculation of the atmospheric neutrino flux (from yields of secondary , K)

Input for Monte Carlo generators (GEANT4, e.g. for LHC or space applications)

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HARP physics goalsHARP physics goals

Precise (~2-3% error) measurement of differential cross-section for secondary hadrons by incident p and ± with:

Beam momentum from 1.5 to 15 GeV/c

Large range of target materials, from Hydrogen to Lead

Thin and thick targets, solid, liquid and cryogenic

K2K and MiniBooNE replica targets

► Acceptance over the full solid angle► Final state particle identifications

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The HARP The HARP CollaborationCollaboration

124 physicists24 institutes

Bari University ,  CERN ,  Dubna JINR ,  Dortmund University ,  Ferrara University ,  Geneve University , P.N. Lebedev Physical Institute ,  Legnaro /INFN ,  Louvain-la-Neuve  UCL ,  Milano University/INFN ,  Moscow INR ,  Napoli University/INFN ,  Oxford University ,  Padova University/INFN ,  Protvino IHEP, Protvino ,  Paris VI-VII University ,  RAL ,Roma I University/INFN Roma Tre University/INFN , Sheffield University , Sofia  Academy of Sciences ,  Sofia  University ,  Trieste  University/INFN ,  Valencia University

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Data taking summaryData taking summary

SOLID:

CRYOGENIC: EXP:

HARP took data at the CERN PS T9 beam-line for 2 years Total: 420 M events, ~300 settings

ElementThickness,

Beam momentum

K2K: Al MiniBoone: Be LSND: H2O

5% 50%

100% Replica

5% 50%

100% Replica

10% 100%

+12.9 GeV/c +8.9 GeV/c +1.5 GeV/c

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Detector layoutDetector layout

Large Anglespectrometer

Forward spectrometer

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Beam detectorsBeam detectorsTOF-A

CKOV-A CKOV-B

TOF-B

21.4 m

T9 beam

MWPCs

Two beam Cherenkov: /K above 12 GeV

~100% e- tagging efficiency

MWPC: incident beam direction with σ<100μm, =96%

Beam TOF:/K/p at low energy

T0 with σ~70ps

Proton selection purity > 98.7%

12.9 GeV/c

K

pd

Corrected TOF (ps)

3 GeV

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Large angle spectrometer: TPCLarge angle spectrometer: TPC

dE/d

xP (GeV/c)

p

PT/P

T

PT (GeV/c)

pt = abs(1 +2) pt √2(tot)

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Large angle spectrometer: RPCLarge angle spectrometer: RPC

•Two groups: barrel and forward plane

•46 chambers;

•2 layers;

•368 pads

•Intrinsic barrel time resolution: ~220 ps

•Combined resolution

(RPC+TPC+BEAM) ~ 330 ps

Bet

a=v/

c

P (GeV/c)

p

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Forward acceptanceForward acceptance

A particle is accepted if it reaches the second module of the drift chambers

mradsx ]200 ,200[P > 1 GeV

K2K interestK2K interest

dipole magnetNDC1 NDC2

B

x

z

NDC5

beam

target

Top view

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22 NDC3

NDC4

Plane segment

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Forward trackingForward tracking

dipole magnetNDC1 NDC2

B

x

z

NDC5

beam

target

Top view

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22 NDC3

NDC4

Plane segment

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3 track types depending upstream information1. Track-Track2. Track-Plane segment3. Track-Target/vertex

recover efficiency and avoid dependencies on track density in 1st NDC module (model dependence)Calculate efficiency separating downstream system first:

vertexdowntrack

DownstreamUpstream

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Tracking efficiencyTracking efficiency

)5().2()5()2( down

P, GeV/c x, rad y, rad

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Tracking efficiencyTracking efficiency

P, GeV/c x, rad y, rad

vertexdowntrack

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Reconstruction efficiencyReconstruction efficiency

P, GeV/c x, rad y, rad

toftrackrecon

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e++

p

number of photoelectrons

inefficiency

e+h+

TOF CHERENKOVCALORIMETER

3 GeV/c beam particles3 GeV/c beam particles

+

p

0 1 2 3 4 5 6 7 8 9 10

p

P (GeV)P (GeV)

e

k

TOFCHERENKOV

TOF CHERENKOV

CHERENKOV

CALORIMETER

TOF

CHERENKOV

CAL

Forward spectrometer: PIDForward spectrometer: PID

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Analysis for K2KAnalysis for K2KIn K2K: In K2K: EE : 0 ~ 5 GeV : 0 ~ 5 GeV

P < 10 GeV/c

< 300 mrad

Most important regionMost important region

oscillation max: oscillation max:

EE ~ 0.6 GeV ~ 0.6 GeV

1 GeV/c < P1 GeV/c < P < 2 GeV/c < 2 GeV/c

< 250 mrad< 250 mrad

E P

P vs

Study interactions of 12.9 GeV Study interactions of 12.9 GeV protons on Al with the HARP protons on Al with the HARP Forward SpectrometerForward Spectrometer

Oscillation maxOscillation max

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Combined PID probabilityCombined PID probabilityBayes theorem:

TOF cherenkov

By MC:

electrons have a peak in low energy;

the particle is rejected if p<2.6 GeV/c and Nphe >15;

where j = p,

By data:

Kaons are estimated

And subtracted

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where:

M – unfolding momentum matrix - between true and measured momentum

J – Jacobian of transformation between measured and ‘true’

- inverse tracking efficiency

- inverse geometrical acceptance

Raw yield for K2K thin targetRaw yield for K2K thin target

twaw

K2K replica targetK2K replica target

5% 5% Al target Al target 200% Al target

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Then:

Corrections for absorption (not reaching downstream detector) ~ 10-20%

Correction for secondary interactions( in the target and not coming from vertex) ~5%

Empty target subtraction

Subtraction of electrons and kaons

PID criteria by

where ij is the fraction of observed j to be true i

True pion and proton yieldsTrue pion and proton yields

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Cross-section calculationCross-section calculationPion cross-section Pion yield

A - atomic number

N0 - Avogadro number

- density

Z – target thickness

Npot – number of protons on target

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7 mln. triggers

3.054 mln. incoming protons

170 000 secondary tracks

+ cross-section (graphics)+ cross-section (graphics)

+ data

… Stanford-Wang fit

PRELIMINARY

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+ cross-section (table)+ cross-section (table)

PRELIMINARY

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ConclusionsConclusionsThe HARP Experiment has collected data for hadron production measurements with a wide range of beam energies and targets

Detector, PID, tracking efficiency well understood and robust

First cross-section data are available: thin (5%) K2K target, using forward region of the detector

In the near future HARP will provide many In the near future HARP will provide many important results, not only for important results, not only for physics physics!!

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MiniBooNE beam phase spaceMiniBooNE beam phase space

Momentum and Angular distribution of pions decaying to a neutrino that passes through the MB detector.

Acceptance of HARP forward detector

8.9 GeV beam interactions on MiniBooNE replica Be target

cooling fins

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yield for the MiniBooNE yield for the MiniBooNE thin targetthin target

Iterative PID algorithm on Be 5% target data to extract raw pion yields.

PRELIMINARY