harp a hadron production experiment - in2p3moriond.in2p3.fr/ew/2002/transparencies/3_tuesday/... ·...

HARP a hadron production experiment

Emilio Radicioni, INFNfor the HARP collaboration

12/03/2002 E.Radicioni - XXXVII Rencontres de Moriond 2

HARP motivations

provide data for neutrino factory / muon collider design.reduce the uncertainties in the atmospheric neutrino flux calculationsget better prediction of neutrino fluxes for K2K and MiniBooNEprovide a calibration sample for hadron generators in MonteCarlosimulation packages

on this last issue we are collaborating with GEANT4


“revival” of hadron production experiments

understanding ν-beam targets, atmospheric ν fluxes and the detailed composition of ν beams relies on knowledge of the hadron production processes.hadron generators (which are – in a way or another - all tuned to existing data) show 30% to 100% discrepancy in their predictions

calibration of hadron generators, apart from the issue of neutrino physics, is essential for any kind of detailed simulation study

Available data is limited, either by statistics (bubble chamber or emulsion experiments), by lack good π to p separation, or by acceptance

Abbott et al: p-Be 14.6 GeV/c

Lundy et al: p-Be 12.5 GeV/c

Allaby et al: p-Be 19.2 GeV/c


“revival” of hadron production experiments

Some data could be already exploited: BNL E910

main goal: Strageness production in p-A collision (comparison with A-A collisions)Some data overlap with our needs6,12,18 GeV/c beam proton momentaBe,Cu,Au targets

howeverlow statistics in general, very low at 6GeV/cno thick targetsno backward acceptance (target outside the TPC)


I- optimizing the ν-factory design

Primary energy, target material and geometry, collection scheme• maximizing the π+,π− production rate /proton /GeV• knowing with high precision (<5%) the PT distributionCERN scenario: 2.2 GeV/c proton linac.

Phase rotation• longitudinally freezethe beam: slow down earlier particles, accelerate later ones• need good knowledge also of PL distribution


II- Atmospheric neutrino fluxes

Primary flux is now considered to be known to better than 10%Most of the 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 leads to about 30% uncertainty in atmospheric fluxesà cryogenic targets

primary flux

µν

µν

eν

−µ

−e

decaychains

N2,O2

+π −π Kp

....hadron

production


G.Battistoni, Now2000

Discrepancies between hadronic generators


III- Measurements of experimental targets

precise understanding of a ν beam spectrum and composition requires hadroproduction data for 2 main reasons:

to calibrate the hadron generators for a particular primary beamenergy and a particular target material. This is achieved by measuring π and K production cross section on thin targetsto be able to reproduce the effect of re-interactions in the target. This is achieved by measuring the cross sections with several targets of different interaction lenght

HARP is measuringAl targets (0.02λ, 0.5λ, 1λ, + K2K replica) at 12.9GeV/cBe targets (0.02λ, 0.5λ, 1λ, + MiniBooNE replica) at 8Gev/c


HARP

secondary hadron yieldsfor different beam momentaas a function of momentum and angle of daughter particlesfor different daughter particles

as close as possible to full acceptancethe aim is to provide measurements with about 2% overall precision à efficiencies must be kept under control, down to the level of 1%

primarily trough the use of redundancy from one detector to anotherthin, thick and cryogenic targetsT9 secondary beam line on the CERN PS allows a 2à15 GeV energy range


HARP

Large event sampleO(106) events per setting

a setting is defined by a combination of target type and material, beam energy and polarity

Fast readout aim at ˜103 events/PS spill, one spill=400ms. Event rate ˜ 2.5KHzcorresponds to some 106 events/dayè very demanding (unprecedented!) for the TPC.

mesurements are needed NOWre-use existing detectors as much as possible

cost effectivenessminimize effort and time-scale


Experimental area & detector layout

target, Inner Trigger Cylinder, TPC and RPCin a solenoid magnet

Forward TriggerPlane

Drift chamberstations

cerenkov

Time Of Flight

electronidentifier

muonidentifier

dipole magnet


Acceptances

Forwardspectrometer

TPC


Acceptances

Acceptance: PT vs PLbox plot for pions produced in 15GeV/c interactions of protons on thin Be targetredundancy in overlap regions


Targets

Cryogenic targets 6 cm long

target tube and standard target holder

82

73

50

29

13

6

4

Z

0.45Sn

0.34Pb

11.140.22Ta

150.30Cu

0.79Al

380.76C

0.81Be

thick(cm)

thin(cm)

target

O2N2D2H2

~65 cm BeMiniBooNE target~60 cm AlK2K target

Solid targets

Special targetsspecial cryogenic target holder


Large-angle detectors: TPC+RPC

beam

TPC field cage

TPC pad plane/readout

target

ITC innertrigger cylinder solenoid

coil

RPC barrel

2.24 m

1.59 m


Large-angle detectors: RPC

Motivationseparation of large-angle e/π below 300MeV/c< 200ps needed resolution not achievable with one-sided readout scintillators (2-sided impossible for mechanical resons).

30 barrel RPCs, 16 forward150 ps resolution99% efficiency

preliminar

y


Large-angle detectors: TPC

1.5m long, 0.8m diameter0.7T solenoidal magnetic field12Kv/m electric field makes the ionization drift to the readout plane with a speed of 5cm/µs à about 30µs total drift timeabout 4000 readout pads arranged in 20 concentric rowsionization level is sampled on each pad in 0.1µs time binsformidable amount of data àonline zero-suppression + fast readoutconstruction:

Aleph’s TPC90 magnetdesign inspired by existing detectors or designs (Aleph, NA49, Alice)readout from Alice/NA45

ITC

RPC

(courtesy M.C. Morone, A. Grossheim)

preliminar

y

studies


forward spectrometer: drift chambers

0.68T dipole magnetfor tracking and momentum measurements in the forward regionDCs from NOMAD, but equipped with new readout electronics (TDCs) for faster readoutDC modules arranged in 4 stations. 1 module = 4x3planes = 4x(-5°,0°,+5°)total of 60 DC planes, 42 wires/plane (˜3k channels)Average hit efficiency 91%, compensate by redundancy in number of planes. Reduced efficiency w.r.t. NOMAD due to different gas mixture (safety constraints)

˜3m


forward spectrometer: CERENKOV

Cylindrical mirrors in a 35 m3 vesselfilled with C4F10

Threshold cerenkov to complement the TOF in the higher energy regionmirrors and mechanical construction are new8-inch photomultipliers are recovered from CHOOZCalibration and efficiency studies are in progress

---97.5 ± 10. %Eff muons

Eff pions >97% @ 95% C.L. (40/40)

>93% @95% C.L. (113/113)

89. ± 10. %

12 GeV5 GeV3 GeV

preliminar

y


forward spectrometer: TOF

~7.4 m

2.5 m

time separation for 3GeV beam particles (π,p)

• overall stability has been continuously verified with cosmic-ray events and laser calibration

preliminar

y


forward spectrometer: e-ID

purpose: separate e from π, as cross-check with the cerenkovmade by one plane of 62 calorimeter modules 5λ thick (EM1) + one plane of 80 modules 11λ thick (EM2)recovered from the CHORUS Pb/scint. fiber calorimeter Detailed calibration and e/ πseparation studies are under way

preliminar

y


forward spectrometer: beam-µ catcher

electron identifier

muon identifier

3.3 m

6.72 m

Electron identifier:Pb/fibre: 4/162 EM modules, 4 cm thick80 HAD1 modules, 8 cm thick

Muon identifier:Iron + scintillator slabsThickness 6.44 λI


less than one year before…


View of the experimental area


Blow-up of the target region


a (not) very typical event


Collected data sample

HARP has collected about 100 millions physics triggers thin Be, Al, Ta, Pb targets at 3, 5, 12 and 15 GeV/c, positive and negative polaritiesthick Ta and Pb target at +3 GeV/csome K2K target measurements at +12.9 GeV/csome MiniBooNE target measurements at +8 GeV/cemtpy target runs for background studies“copper button” target runs to assess the ability to reconstruct the shape of the target+ cosmics, and various types of calibration events


Present status of the analysis

low energy (3GeV/c)beam particle composition and contaminationslarge angle (all angles covered by the barrel-RPCs)

RPC calibration and time resolutionTPC calibration and equalizationTPC clusteringTPC track finding and fittingparticle ID (e,π,K,p)

will try to have the first dn/dpdη with an error of the order of 5% by end of March 2002


Perspectives for 2002 data taking

Exploiting the shutdown for understanding the detector and improving the calibrationthe PS beam will restart in Mayà cryogenic targets (H2, D2, N2, O2)à final K2K and MiniBooNE statisticsà complete the measurement on standard targets with all beam momenta and both polarities


Follow-up

complement the HARP measurements with higher momentarelevant for

higher energy ν-fact proton drivershigher energy region of hadroproduction for atmospheric neutrinostudiesstudy the beam composition of higher-energy traditional beams, like the NuMI beam (120GeV/c) or the proposed JHF super-beam (50GeV/c proton driver)

the HARP community has proposed to use the NA49 apparatus at CERN for this purpose.

NA49 has been built for detailed studies of particle production in Pb-Pb collisions at high energiesIt may be used as-is for our purposes

An interesting option is given by the fact that E907 at FNAL is getting momentum from Livermore joining the effort.

E907 has plans for a wide range of measurements, among which relevant ones for neutrino physics


Follow-up: HARP/NA49 ?particle ID in the TPC is augmented by TOFsleading particles are identified as p or n by a calorimeter in connection with tracking chambersrate somehow limited (optimized for VERY high multiplicity events).

order 106 event per week is achievable

NA49 is located on the H2 fixed-target station on the CERN SPS.secondary beams of identified π,K,p; 40 to 350 GeV/c momentum

Relevant for atmospheric neutrinos and NuMI beam


Follow-up: E907 @ FNALproposed on the FNAL main injector, seconday beams of π,K,p; 5 to 120 GeV/cIn addition to tests of scaling lows in high-energy particle production, nuclear and heavy-ions physics, E907 is relevant for atmospheric neutrinos, NuMI beam, higher-energy proton drivers for ν-factoriesAs in all of the previous cases, it is an open-geometry spectrometer.TPC+spectrometer, complemented with TOFs and ring-imaging Cerenkovaiming at the same precision level as HARP: 2%Planning for data points with statistics of 3·106 events. One data point would take about 6 days.


Conclusions

HARP has successfully completed the first round of data takingData are being analysed, first results will soon be availableThe desired data sample will be completed in 2002Already proposed experiments will extend HARP’s measurements to higher energies

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