# Presentation: 361058

## From NuInt05 - almost verbatim

**    ****A.Curioni - WIDG March 29 2006**
**From NuInt05 - almost verbatim**

## Experimental study of quasi-elastic neutrino interactions on Ar with an ICARUS liquid Ar TPC exposedto the WANF neutrino beam

**Alessandro Curioni**
- On behalf of ICARUS-MILANO U. collaboration

## Outline of the talk

*Give you some background*
*Describe the experimental setup and data analysis procedure*
*Present the results from the analysis of a sample of QE events: measurement of nuclear effects in   nu-Ar interactions *

## Some historical background:

*The test took place in 1997, to measure distortions to the simple QE kinematics due to the presence of nuclear matter - e.g. an excess of events with large missing transverse momentum. *
*The test was run jointly by the ICARUS collaboration and a group from Milano U. and INFN (and more than a little help from the NOMAD collaboration)*

## Data taking: from Aug to Nov on the WANF nu-beam (detector commissioning and PS fire: Apr to July)
1.21 1019 pot
81,000 triggers recorded
10% of which recognized as neutrino CC events
Published so far:
F. Arneodo et al. (ICARUS-Milano U. coll.)
   hep-ex/9812006
A. Curioni -Tesi di Laurea 1998 - Milano U. (in Italian)
B. Boschetti -Tesi di Laurea 1998 - Milano U. (in Italian)
ICARUS coll. - NIM A 449 42-47, 2000 (using data from the test beam)		

- 1.21 1019 pot
- 81,000 triggers recorded
- 10% of which recognized as neutrino CC events
- Published so far:
- F. Arneodo et al. (ICARUS-Milano U. coll.)
-    hep-ex/9812006
- A. Curioni -Tesi di Laurea 1998 - Milano U. (in Italian)
- B. Boschetti -Tesi di Laurea 1998 - Milano U. (in Italian)
- ICARUS coll. - NIM A 449 42-47, 2000 (using data from the test beam)

## TEST SETUP: BEAM

- WANF nu-beam:
- 450 GeV p extracted every 14.4 s in two 6 ms spills, 2.5 s apart. 1.8 103 pot per spill on a Be target
- Mean energy of the nu-beam  **24.3 GeV**
- Contamination: 7% anti-numu, 1% nue
- The LAr TPC was sitting right in between CHORUS & NOMAD (hall 191) on a platform 4.5 m high

**Preliminary**

## TEST SETUP: Lar TPC

- Fiducial volume 32 x 32 x 46.8 cm3, 67 kg of Ar
- 2 x 128 wires, 2.54 mm pitch
- S/N for a m.i.p. ~11
- All wire signals digitized and recorded
- LAr purity stable ~4.2 ms electron lifetime (~4 m drift)
- LAr doped with 3.5 ppm of TMG to linearize charge (see next)
- GOAL: IDENTIFY THE QE TOPOLOGY / MEASURE THE MOMENTUM OF THE PROTON (see next)

## TEST SETUP: trigger & veto

- 5 plastic scintillators 50 cm upstream the TPC as **veto**, plus the last CHORUS scintillator plane
- 3 plastic scintillators downstream the TPC as **trigger **(efficiency 97%), plus two NOMAD scintillator planes T1 & T2
- Dead time: TPC ~3%, NOMAD 15%
- An alternative trigger for through-going muons for calibration (alignment to NOMAD etc.)

## Muon SPECTROMETER

- NOMAD magnetic dipole as magnetic spectrometer
- pure NOMAD:
- p / p  ~ 0.05 L-1/2  0.008 p L-5/2 (~2%)
- NOMAD FWD calorimeter (~190 cm of iron):
-  **~ 140 MeV / c**  on each component in the transverse plane

**Preliminary**

## Evt 1: generic DIS

- Transverse plane

- nu-beam

**DFT FILTER**

## Evt 2: CC π0

## Evt 3: QUASI ELASTIC (2.5%)

## PROTON MOMENTUM

- For contained protons, |p| measured from range; uncertainty ~7 MeV/c for |p|~400 MeV/c, due to the pitch of the wires
- Angular resolution: depends on N, # of wires         ~0.36 (12)1/2 N-3/2 / 2.54 (15 mrad for N=10)
- Lower threshold on K.E. to measure the direction: ~50 MeV
- For non-contained protons |p| from dE/dx
**HERE I WILL RESTRICT MYSELF TO CONTAINED PROTONS, K.E. > 50 MeV**

## ASIDE: non-contained protons

- If proton not contained, K.E. can still be reconstructed fitting the dE/dx for the visible part of the track
- Not done in a systematic way for this work
- Easier: from dE/dx one can tell non-contained protons from pions with ~100% discrimination, and recover a larger QE sample (but I won’t discuss it any further)

**Preliminary**

## THE GOLDEN SAMPLE

- Use only a “golden sample” of QE, defined as:
- Distance of the interaction vertex from any of the TPC walls > 1cm
- Muon candidate track at least 12 wires long & associated with a muon in NOMAD
- Proton contained and K.E. > 50 MeV
- More stopping particles are accepted if their range implies K.E. < 50 MeV for a proton (20 MeV for a pion)
- No tracks other than the muon leaving the TPC
- No gammas > 10 MeV
- Efficiency of the “proton requirements” ~20%
**Eventually, 61 events selected (73 expected from MC)**

## WHAT WE MEASURE

**THE FULL KINEMATICS OF THE QE EVENTS, in particular:**
**Missing transverse momentum:** for QE scattering on a free proton,  pTmiss ~ 0. For a proton bound in a Ar nucleus ~250 MeV/c on average (Fermi motion), and a tail to larger pTmiss
**Acolinearity:** defined as (transverse plane x-y)
-     acos { (pxpxp + pypyp) (px2 + py2)-1/2(pxp2+pyp2)-1/2 }
- ~0 for scattering on a free proton
**WHICH ARE SENSITIVE TO THE PRESENCE OF NUCLEAR MATTER**

## COMPARED TO THE MODELS:

**FLUKA** code (www.fluka.org):                10,000 quasi-elastic events (final state). Fermi motion, Pauli blocking, hadronic re-interactions inside the nucleus
**SW**: a model (ICARUS TM 87/27 - 1987) which includes only Fermi motion and Pauli blocking, with a Saxon-Woods potential
- A sufficiently (see next) accurate description of the experimental setup

## BACKGROUND

- ∆+ and ∆++ with pion absorption in the nucleus: **IRREDUCIBLE**, but included in the MC (FLUKA)
- Final State -n-+ : **~0 EVT. **(i.e. *no* pion-proton mis-ID)
- CC π0 where both gammas don’t convert in the TPC. From MC (FLUKA) **13% CONTAMINATION** (20% probability to miss both gammas). 				Checked against the data themselves: select “golden events” with 1 (N1) or 2 (N2) identified gammas from π0 decay.
-   N1 = 2N(1- ) ; N2 = N 2 ; N unknown, want to find 2
-                 2 = 32±10 % (20% from MC)

## RESULTS

- Some kinematics variables are only marginally affected by the presence of nuclear matter: they allow a consistency check

***Proton K.E. dominated by ***
***the requirements***
***K.E.****** > ******50 MeV***
***Full containment****** ***

**Preliminary**

## _x0016_ RESULTS 

- Purely leptonic variables: affected by the presence of nuclear
-  matter only through Fermi motion & Pauli blocking

**Preliminary**

## RESULTS 

*The simplistic SW model doesn’t reproduce the tails in *
*Missing Transverse Momentum and Acolinearity. *
*QUANTIFY ...*

**Preliminary**

## RESULTS 

- Kolmogorov probabilities (CC π0 BKGD  subtracted) :
- FLUKA             0.30                                 0.52
- SW                  0.027                               0.003

**Preliminary**

## OUTLOOK & CONCLUSIONS

- We have performed the first measurement of nuclear effects in nu-Ar interactions using a LAr TPC
- We see some of the underlying physics and can start telling one model from another even with limited statistics, thanks to a very clean sample and full reconstruction of the kinematics
- Watch out for the complete final analysis and the upcoming paper!

## Post-NuInt05_x0018_(1)_x0013_ 

- *new* analysis done in Granada (ICARUS)
- ~10 more evts mainly from relaxing selections
- basic results confirmed
- draft was reviewed two weeks ago, final paper to be submitted soon
- Proceedings for NuInt05 submitted
- REALLY NEW analysis possible

## Post-NuInt05_x0018_(2)_x0013_ 

- HARDWARE: progress here at Yale (Gibbs 5th floor) toward a detector with the same capability
- New interest for an ~100 ton LAr TPC on the NuMi beam (Bonnie’s talk at CRYODET @LNGS 2 weeks ago)
- Collaboration for very large (10-100 kton) LAr detector (?)