# Presentation: 454813

## Results from the HARP Experiment 

- Silvia Borghi
- Université de Gèneve
*On Behalf of the HARP Collaboration*

## HARP

- 	Systematic study of hadrons produced by incident p and ± with pbeam from 1.5 to 15 GeV/c, more than 420 M pot
- Large range of target materials,
- 	from H to Lead of different length;
- Also measurements on specific targets
- 	of existing  beams: K2K and MiniBooNE

|  | Target
material | Target length 
() | Beam
Momentum (GeV) | #events
(millions) |
| --- | --- | --- | --- | --- |
| Solid targets | Be  | 
2 
(2001)

5

100 | 
±3
± 5
± 8
± 12
± 15

Negative only 2% and 5% | 233.16 |
|  | C  |  |  |  |
|  | Al  |  |  |  |
|  | Cu  |  |  |  |
|  | Sn  |  |  |  |
|  | Ta  |  |  |  |
|  | Pb  |  |  |  |
| K2K | Al | 5, 50, 100, replica | +12.9 | 15.27 |
| MiniBooNE | Be |  | +8.9 | 22.56 |
| Cu “button” | Cu |  | +12.9, +15 | 1.71 |
| Cu “skew” | Cu | 2 | +12 | 1.69 |
| Cryogenic
targets | N7 | 

6 cm | ±3
± 5
± 8
± 12
± 15 | 58.43 |
|  | 08 |  |  |  |
|  | D1 |  |  |  |
|  | H1 |  |  |  |
|  | H2 | 18 cm | ±3, ±8, ±14.5 | 13.83 |
| Water | H20 | 10, 100 | +1.5, +8(10%) | 9.6 |

- Silvia Borghi

- Panic 2005, 24th October 2005

## Experimental setup

- Silvia Borghi

- Panic 2005, 24th October 2005

**Notes:**
Large angle spectrometer: pion yield in p-Ta collisions at 3 GeV/c

Forward spectrometer: 
cross section of positive pions in p-Al collisions at 3 GeV/c
cross section of positive pions in p-Be collisions at 3 GeV/c

## Calculation of a cross section of positive pions

**Calculation of a cross section of positive pions**

**Number of particles observed as ********’ type in bins of reconstructed (p****i’****,********j’****), N(E) refers to data without target (correction for primary proton interactions out of target)**

**number of protons on target**

**Number of target nuclei and target thickness**

**Correction matrix, i.e. unfolding of true ij******** variables from reconstructed i’j’********’ reconstructed efficiency, acceptance, absorption, pion decay, tertiary production, PID efficiency and contamination... **
**Unfold detector resolution (I=true, j=rec)**

- Silvia Borghi

- Panic 2005, 24th October 2005

## ForwardReconstruction

**Angular resolution**

**Momentum resolution**

- 0.5 GeV/c bins p< 4GeV/c and 1.5 GeV/c bins for 5-6.5 GeV/c; 30 mrad angular bins

- P is measured (downstream segment + upstream constraint)
- PID detectors (TOF, CHE)

**Forward****Reconstruction**

- Silvia Borghi

- Panic 2005, 24th October 2005

## PID detectors

**PID detectors**

***CALORIMETER***

- 0       1      2       3      4       5      6       7       8      9      10

- p

- P (GeV/c)

- e

- k

***TOF***

***CERENKOV***

***TOF ***

***CERENKOV***

***CERENKOV***

**TOF**

**CERENKOV**

- Silvia Borghi

- Panic 2005, 24th October 2005

## Evaluation of the measurement precision

- Systematic error evaluation on all the terms of the cross-section, to quantify errors on differential and integrated cross section.

- Dominant error contributions to diff:
-  overall normalization
-  tertiary subtraction
-  momentum scale

- average error:
-  ******diff****=8.2%**

-  for 0.75 < p< 6.5 GeV/c and 30<<210 mrad, error: ******int****=5.8%**

- Dominant error contributions to int:
-  overall normalization
-  tertiary subtraction

- Silvia Borghi

- Panic 2005, 24th October 2005

## HARP results: p+Al++X cross-section pbeam=12.9 GeV/c

**HARP results: p+Al********+****+X cross-section ****p****beam****=12.9 GeV/c**

- Silvia Borghi

- Panic 2005, 24th October 2005

## Physics impact: Far and Near  fluxes at K2K

- Similar E spectra arising from K2K default (pre-HARP) and HARP Sanford-Wang + parameterization
- Errors shown: HARP + production uncertainties and K2K MonteCarlo
- The error in R associated with the HARP measurement is of the order of 1%.

- Silvia Borghi

- Panic 2005, 24th October 2005

## The production cross section of pions in p-Be collisions

**Primary protons**
**From Fermilab Booster**
**P****p****= 8.9 GeV/c**

- Silvia Borghi

- Panic 2005, 24th October 2005

## HARP results: p+Be++X pbeam=8.9 GeV/c 

**HARP results: p+Be********+****+X p****beam****=8.9 GeV/c **

-  primary protons: 7.3 M
- pbeam=8.9 GeV/c
-  5%  Be disc
-  quite similar Al data
-   analysis well covering
-   MiniBooNE phase space
**0.75 < p< 5 GeV/c **
**       ****30< ******** < 210 mrad**

- Sanford-Wang parametrization fit

- Preliminary

- Preliminary

- Silvia Borghi

- Panic 2005, 24th October 2005

## Large Angle Region 

- Silvia Borghi

- Panic 2005, 24th October 2005

## HARP results: p+H2p+p (elastic scattering) pbeam=3 GeV/c

- Elastic scattering: p (and π) on H2 target  1- or 2- prong final state
- Cinematic selection, cuts on dE/dx (PID)

- The missing mass plots show:
- The missing mass value is corrected  the momentum scale is correct
- The cross section is comparable with the PDG one  the efficiency and the systematic are under control

- Cross section = 6.1 mb

- Silvia Borghi

- Panic 2005, 24th October 2005

## Nufact physics case: maximize ± production rate

**Optimize:**
- target material and geometry
- primary beam energy
- collection scheme

- Experimental data are poor
-   (small acceptance, few materials)
-   and old (Allaby et al.1970,
-   Eichten et al. 1972)

- Existing simulation packages show
-    large discrepancies on pion yields
-    and distributions

- Silvia Borghi

- Panic 2005, 24th October 2005

## HARP results: p+Ta+X pbeam=3 GeV/c 

**HARP results: p+Ta********+X**** ****p****beam****=3 GeV/c**

- One beam particle identified as proton by MWPC and TOF beam counters
- large angle interaction by ITC (≥99%)
- Cuts on the event spill to reject events strongly affected by the dynamic distortions
- 0.785<  <1.83  rad  &    100 < pt < 700 MeV/c

- Silvia Borghi

- Panic 2005, 24th October 2005

## Conclusion

- Thin target analysis for Al (at 12.9 GeV/c, K2K) for + production: cross sections have been measured within 6 % uncertainty (8.2% point-to-point) in the forward region. Physics impact in K2K strong reduction of systematics of Far to Near neutrino flux ratio associated to secondary particle production
- Thin target analysis for Be (at 8.9 GeV/c, MiniBooNE) for + production in forward direction is almost completed
- On going analysis of thick and replica K2K and MiniBooNe targets, +/-, K/, A and energy dependence
- Carbon results are expected to make a major contribution to the understanding of neutrino fluxes for accelerator neutrinos as well as atmospheric neutrino fluxes.
- The analysis of  production for Ta at large angle already produced preliminary results. The goal is to give an experimental input to choose the proton driver energy of the Neutrino Factory

- Silvia Borghi

- Panic 2005, 24th October 2005

## Beam Detectors

- Silvia Borghi

- Panic 2005, 24th October 2005

## PID detectors

**PID detectors**

***CALORIMETER***

- 0       1      2       3      4       5      6       7       8      9      10

- p

- P (GeV/c)

- e

- k

***TOF***

***CERENKOV***

***TOF ***

***CERENKOV***

***CERENKOV***

- Silvia Borghi

- Panic 2005, 24th October 2005

## PID performance and migration matrix

***pions***

***protons***

- pion efficiency

- pion purity

- PID corrections computed in bins of momentum and angle

- Correction matrix, i.e. unfolding of true ij variables from reconstructed i’j’’ reconstructed efficiency, acceptance, abosorption, pion decay, tertiary production, PID efficiency and contamination

- Silvia Borghi

- Panic 2005, 24th October 2005

**Notes:**
Efficiency dei pioni e’ al disopra del 90 % e I protoni residui solo few %
The elctron veto has effect on pion efficiency only of few %
Instead the kaons subtraction is relevent 3% only in the region between TOFW and CHE aroun 3GeV/c

## p+Al++X : results versus previous data

- Silvia Borghi

- Panic 2005, 24th October 2005

## p+Be++X : results versus previous data

**Reasonable agreement, differences for ********>150 mrad **

- Pbeam: 10÷15 GeV/c close to MiniBooNE
-  < 200 mrad
- HARP Sanford-Wang parameterization at 8.9 GeV rescaled to pbeamof old experiments

- Silvia Borghi

- Panic 2005, 24th October 2005

## p+Be++X : results versus previous data

**Important variations w.r.t. Cho71 old data (Cho71 data are in disagrement also with BNL E910...)**

- Silvia Borghi

- Panic 2005, 24th October 2005