Measurement of Inclusive Neutral Current Neutral Pion Production

Measurement of Inclusive Neutral Current Neutral Pion Production on Carbon in a Few-Ge. V Neutrino Beam ar. Xiv: 0910. 5768 [hep-ex] K. Hiraide November 5 th, 2009 ICRR colloquium 1

Contents • Sci. Boo. NE experiment • Analysis and results – Measurement of s(NC-p 0)/s(CC) ratio – NC coherent pion production • Summary 2

Sci. Boo. NE experiment (FNAL E 954) Booster Neutrino Beam • Precise measurements of neutrino- and antineutrino-nucleus cross sections near 1 Ge. V • Essential for future neutrino oscillation experiments • Neutrino energy spectrum measurements • Mini. Boo. NE/Sci. Boo. NE joint disappearance • e constraint for Mini. Boo. NE 3

Booster Proton accelerator • 8 Ge. V protons sent to target Target Hall • Beryllium target: 71 cm long 1 cm diameter • Resultant mesons focused with magnetic horn To Mini. Boo. NE Sci. Boo. NE • Reversible horn polarity 50 m decay volume • Mesons decay to & • Short decay pipe minimizes edecay Sci. Boo. NE located 100 m from the beryllium target Sci. Boo. NE 4

Booster Neutrino Beam (BNB) Expected neutrino flux at Sci. Boo. NE (neutrino mode) • mean neutrino energy ~0. 7 Ge. V • 93% pure beam • anti- (6. 4%) • e + anti- e (0. 6%) • antineutrino beam is obtained by reversing horn polarity 5

Sci. Boo. NE detector Muon Range Detector (MRD) Sci. Bar • scintillator tracking detector • 14, 336 scintillator bars (15 tons) • Neutrino target • detect all charged particles • p/p separation using d. E/dx Used in K 2 K experiment • 12 2”-thick steel + scintillator planes • measure muon momentum with range up to 1. 2 Ge. V/c n Parts recycled from Past experiment at FNAL Electron Catcher (EC) 4 m 2 m • spaghetti calorimeter • 2 planes (11 X 0) • identify p 0 and e Used in CHORUS, HARP and K 2 K 6

Sci. Boo. NE data-taking Number of Protons on target (POT) • Jun. 2007 – Aug. 2008 • 95% data efficiency • 2. 52 x 1020 POT in total • neutrino : 0. 99 x 1020 POT • antineutrino: 1. 53 x 1020 POT 7

Neutral current p 0 production 8

NC inclusive p 0 at Sci. Boo. NE NC neutrino interaction in which at least one p 0 is emitted in the final state from the target nucleus 9

Event selection 1. Pre-selection cuts • At least two tracks • 1 st layer veto 2. Muon track rejection cuts 3. Track disconnection cut 4. Electron catcher cut 5. Number of photon tracks 6. Reconstructed p 0 vertex cut 7. Reconstructed p 0 mass cut 10

CC event rejection in Sci. Bar Muon track rejection using decay electron p, p CC event Track disconnection cut 11

CC event rejection using EC Events are selected if one of the following condition are satisfied: 1. No matched EC cluster 2. E 1>150 Me. V 3. REC=E 2/E 1<0. 2 E 1 E 2 Sci. Bar EC 12

“Extended” track ( photon track candidate) Requiring non-proton like Merging two or more tracks If they are nearly co-linear Muon Confidence Level (Mu. CL) Particle ID variable based on d. E/dx 13

Dirt background rejection Vertex resolution ~12 cm 14

Reconstructed p 0 mass 50 Me. V/c 2<Mp 0<200 Me. V/c 2 • 657 events are selected after all cuts • 240 BG events expected • Selection efficiency: 5. 3% 15

CC inclusive event sample (for normalization) MRD-stopped Sci. Bar EC MRD muon • Muon is identified using MRD • The track should start from Sci. Bar fiducial volume • Muon stops in MRD 16

s(NC-p 0)/s(CC) cross section ratio 17

Reconstructed p 0 kinematics 18

Corrected p 0 kinematics • Subtract the expected BG • Convert the reconstructed momentum (angle) to the true ones using unfolding method • Perform the efficiency correction 19

NC coherent pion extraction Fit Ep(1 -cos qp) distribution with two fitting parameters Rcoh: NC coherent p scaling Rres: NC resonant p scaling 20

Summary • Sci. Boo. NE has measured NC p 0 production on polystyrene target. • s(NC-p 0)/s(CC)=(7. 7+/-0. 5(stat. )+/-0. 5(sys))x 10 -2 at mean neutrino energy 1. 1 Ge. V. • The measured shapes of the p 0 momentum and angular distributions agree with the MC prediction based on the Rein. Sehgal model. • s(NC-coherent p 0)/s(CC)=(0. 9+/-0. 5)x 10 -2 • This result is consistent with the Rein-Sehgal model. • Submitted to Phys. Rev. D 21