Results of the HARP experimentPart 2

I.Boyko, Yu.Nefedov

Particle identification

π+π-

p

The HARP split

• At the begin of the data analysis, HARP broke into two parts over a deep split of opinion on quality of work, working methods, and professional ethics.– 'HARP Collaboration' or 'Official HARP' (OH)– 'HARP-CDP group' (CERN, Dubna, Protvino)

• In this seminar, we represent HARP-CDP• Between OH and HARP-CDP, only the raw data

and the computing infrastructure are common. The analysis strategies and software are totally independent.

The “500 ps effect”

• Citation from 2008 JINST 3 P04007: `The remaining difference observed … is of the order of (150±100) ps at 450 MeV/c’

ΔT = 480-130 = (350±40)ps

480±30 ps

130±20 ps

Δt

(ns)

What is wrong with OH calibration

• Momentum bias Δ(1/PT) = 0.3 (c/GeV)

• Poor momentum resolution σ(1/PT) = 0.55-0.65 (c/GeV)– CDP: 0.20-0.25 (c/GeV)

• TOF resolution: σ(TOF) = 305 ps– CDP: σ(TOF) = 175 ps

• Unphysical “500 ps effect” in RPC

Comparison of GEANT4 hadronic models with the HARP-CDP data

GEANT4 (LHEP) angular spectrum of π+ produced by 8.9 GeV protons

GEANT4 versus HARP-CDP data

The “LSND puzzle”

On the “LSND puzzle”

• LSND: anomalous 4 σ signal of anti-νe from the interactions of Ekin=800 MeV protons in water.

• LSND interpretation: – anti-νμ → anti-νe oscillations– with Δm2 ~ 1 eV2

• Sterile neutrinos?• MiniBooNe disagrees with

LSND• Question: is π-/ π+ ratio correct?π+

π-

μ+

νμ

μ-

_νμ _

νe

νμ

e-

e+

_νμνe

p+H2O

π-/ π+ ratio: LSND vs HARP-CDP

LSND parametrizationLSND parametrization

Production of hadrons by +8.9 GeV/c and -8.0 GeV/c

proton and pion beams on 5% λ Be target

What we measure

p π+ π- K+ d

p

π+

π- -

Secondary particle

Bea

m

Some cross-section plotsPositive pion beamNegative pion beam

Comparison with OH

Comparison with E910

E910: 1.5 m long flat-geometry TPC

• HARP-CDP is going to publish lots of precise cross-sections of hadron production on nuclei.

• 'Official HARP' publish cross-sections that are wrong by factors up to two (to our regret, with participation of JINR Dubna authors).

• 'Official HARP' consciously ignore:– the conclusions of the CERN/INFN Review Board for HARP

(chairman L. Foa): '...The RBH finds clear evidence for a significant momentum bias in the OH analysis...the RBH finds no evidence if any significant momentum bias in the CDP analysis...'

– the conclusions of the CERN-SPSC Review (chairman J. Dainton): '...This calls into question the validity of the results in recent publications by the HARP collaboration of their large angle data, based on analysis (a)[=OH]...‘

– our published calibration work of the TPC and the RPCs

Backup slide