Last Update: October 2000

HARP

Collaboration: Bari, Legnaro, Milano, Ferrara, Napoli, Padova, Roma I , Roma III, Trieste

Laboratory and Beam: CERN, CPS proton and pion

1 Goal of the Experiment

The HARP experiment is a measurement of hadroproduction, the first phase of a wide ranging campaign meant to reduce the uncertainties induced by hadroproduction in the field of neutrino physics.

The HARP experiment will carry out, at the CERN PS, a programme of precise measurements of secondary hadrons,over the full solid angle, produced on thin and thick nuclear targets by beams of protons and pions with momentum in the range 2 to 15 GeV/c.

The main motivation is twofold: to acquire adequate knowledge of pion yields for an optimal and quantitative design of the proton driver of the neutrino factory; and to improve substantially the calculation of the atmospheric neutrino flux which is needed for a refined interpretation of the evidence for neutrino oscillation from the study of atmospheric neutrinos in present and forthcoming experiments.

Stage 1 of the HARP experiment was recommended for approval by the SPSC on 1 December 1999, and was approved by the Research Board on 17 February 2000 as PS214, for data-taking in the East Area's T9 beam until the end of 2001.

Stage 2 of the experiment is planned for the first half of 2002. In Stage 2, the primary proton target would be removed and deuterium and helium nuclei would be sent directly to the target of the experiment, which represents a substantial effort on the accelerator side. If the feasibility of Stage 2 can be ascertained, a proposal will be submitted in due course.

Although the dominant uncertainties in the atmospheric neutrino fluxes ill be greatly reduced by Stages 1 and 2 of HARP, an extension to higher beam momenta in Stage 3, up to 120 GeV/c, is also under serious discussion among interested parties. The NA49 apparatus in the North Area is adequate for these measurements. That programme would extend reliable calculations of atmospheric neutrino fluxes into the 100 GeV/c region and would permit measuring the pion yield of the neutrino target of the MINOS experiment at Fermilab.

The HARP experiment comprises a large-acceptance charged-particle magnetic spectrometer of conventional design, located in the East Hall of the CERN PS and using the T9 tagged charged-particle beam. The crucial detector for low-energy secondaries is a cylindrical TPC inside a solenoid magnet which surrounds the target. Downstream, the TPC is complemented by a forward spectrometer with a large dipole magnet. The TPC, together with the forward spectrometer,ensures nearly full 4 p coverage for the momentum measurement of charged secondary particles.

Their identification is achieved by dE/Dx in the TPC, by time of flight (TOF), by a threshold Cherenkov detector, and by an electromagnetic calorimeter. The experiment re-uses a lot of existing equipment, notably calorimeter modules from the CHORUS experiment and drift chambers from the NOMAD experiment.

2 Physics achievements during 2000

The HARP apparatus has been largely built and installed during the year 2000. A technical run has taken place from 25 September to 25 October 2000. Physics data-taking is planned throughout the PS beamtime in 2001.

In the technical run, the TPC, the RPCs, the Cherenkov detector, the electron identifier and the TOF wall have not yet been available as the construction schedule of these sub-detectors did not permit their availability at this early time. A few protype units of both electron identifier and TOF wall were however successfully tested. In general, the technical run fulfilled a number of well-defined and valuable aims. The Collaboration was able to

optimize the T9 beam between 2 and 15 GeV/c;

put specific beam instrumentation largely in place;

get the experimental area and its infrastructure operational;

install the solenoid and dipole magnets in place and powered;

have one solid target mounted;

have inner TPC trigger and forward trigger hodoscope operational;

have NOMAD drift chambers (almost) operational;

have beam-muon identifier operational;

have draft version of the DAQ program operational;

have data storage/retrieval in the OBJECTIVITY database operational;

have draft version of the GEANT4-based simulation program operational;

have draft version of the reconstruction program in the GAUDIno framework operational.

and collected very valuable data, simultaneously with all detector available, using a preliminary beam interaction trigger, for many days at the end of the technical run.

The construction schedule of the missing sub-detectors will permit data taking with a complete detector in 2001. The schedule is tight; however, at present there is nothing known which calls that plan into question.

3 INFN contributionto the experiment

I NFN contributes to the experiment about 1/3 of is manpower, with about 30 researchers (15 FTE) supported by their mechanical and electronics workshops. The financial contribution to the apparatus is about 1200 Mlit, also about 1/3 of its total cost.

4 Number of publications in referred journals: 0 for the time being, several conference proceedings in the press.

5 Number of talks to conferences: 4 by INFN members of the Collaboration plus a few others

6 Number of thesis on HARP: 4 laurea thesis started, more coming

7 Leadership role in the experiment

A. Guglielmi(PD), V. Palladino(NA) and E. Radicioni(BA) are respectively project leader of TOF (PD+MI), E-identifier (FE,NA,Roma I and III) and DAQ(BA). P. Zucchelli, CERN staff on leave from INFN-Ferrara is project leader of the TPC, where LNL collaborates. TS collaborates to the Cerenkov . INFN groups have large responsabilities in all aspects of software.

8 Innovative instruments

The TPC , including its electronics , is a first class modern device, thriving on the experience of the ALEPH and ALICE TPC’s, among many others. All subdetectors are state of the art devices.

9 Competitive experiments: none, at the moment, of comparable promise.

10 International reviews

HARP was reviewed and approved by the CERN SPSC and Research Board and later by INFN Commissione II.