Sam Zeller, NO-VE Workshop, 02/07/06 1

Neutrino and Antineutrino Cross Sections at MiniBooNE

Sam ZellerColumbia University

(for the MiniBooNE collaboration)

NO-VE WorkshopFebruary 7, 2006

- our 1st cross section

results (CC +/QE)

- future directions in MiniBooNE

program

Sam Zeller, NO-VE Workshop, 02/07/06 2

MiniBooNE is a Oscillation Experiment

• main goal: confirm or rule out e LSND results

• search for → e oscillations

• not going to be showing oscillation results

• working hard on performing a very careful e appearance analysis …

• you’ll have to stay tuned

Sam Zeller, NO-VE Workshop, 02/07/06 3

* well-suited for low E cross section physics

- useful to the community - important for oscillation analysis

- will tell you about

* plus some new opportunities (mention at end)

- antineutrino data! (big change for us)

MiniBooNE On the Way

MiniBooNEis a dynamicexperiment

• while designed for e oscillation search …

updating is

important

Sam Zeller, NO-VE Workshop, 02/07/06 4

Previous Measurements• most of present low energy knowledge comes from bubble chamber exps

• early experiments at ANL, BNL, FNAL, CERN, Serpukhov, etc.

• 20-100% errors due to: - low statistics (100’s of events)

- uncertainties in flux

• in addition to large errors, results often conflicting (some care in interpreting)

• data useful to constrain our MCs

• idea of caliber of past data …

GGM

BNL

FNAL

Sam Zeller, NO-VE Workshop, 02/07/06 5

Low Energy Cross Sections

MINOS, NuMIK2K, NOvA

MiniBooNE, T2K

Super-K atmospheric

predictions from NUANCE

- MC which MBooNE uses

- open source code

- supported & maintained by D. Casper (UC Irvine)

- standard inputs (common ingredients - osc exps)

- Smith-Moniz Fermi Gas - Rein-Sehgal 1 - Bodek-Yang DIS

Sam Zeller, NO-VE Workshop, 02/07/06 6

Low Energy Cross Sections

MINOS, NuMIK2K, NOvA

MiniBooNE, T2K

Super-K atmospheric

• imperative to precisely predict signal & bkgd rates for future oscillation exps

- will be more sensitive to sources of syst error

- nuclear targets! (most past data on H2, D2)

• further motivates need for new measurements

• new data adding new info; revealing interesting features K2K, NOMAD, MiniBooNE

Sam Zeller, NO-VE Workshop, 02/07/06 7

magnetic horn: meson focusing

decay region:  K→

movable absorber: stops muons, undecayed

mesons

“LMC” measure K flux in-situ

450 m earth berm:

magnetic focusing horn

FNAL 8 GeV Booster

MiniBooNE detector

(CH2)

MiniBooNE Beamline• >700,000 contained events

• providing a valuable sample to study low E cross sections

Sam Zeller, NO-VE Workshop, 02/07/06 8

Flux at MiniBooNE Detector

MC predicted energy spectrum

mainly from

production constrained by global data & E910 … - eventually HARP

- really advance knowledge of low E hadroproduction (see Gibin’s talk)

• incident on detector: high purity beam (>99% flavor)

PRELIMINARY

Sam Zeller, NO-VE Workshop, 02/07/06 9

Flux at MiniBooNE Detector

MC predicted energy spectrum

- <E>MBooNE ~ 0.7 GeV

- well-suited for low energy cross section studies

- small tail; enjoy smaller backgrounds from higher multiplicity interactions

- complementary to other experiments <E

K2K> ~ 1.3 GeV <E

NuMI > ~ 10 GeV <E

NOMAD > ~ 24 GeV

PRELIMINARY

Sam Zeller, NO-VE Workshop, 02/07/06 10

Event Fractions at MiniBooNE

- 48% CC QE- 31% CC

- 8% NC 0

- 5% CC 0

- 3% NC +/-

- 4% multi-- 1% NC elastic

MiniBooNE flux-averaged event compositions

(NTANK>200, NVETO<6)

demonstrateunderstanding

of 79% of events before

analyzinge

(<1% of total)

this flux spectrum dictates whattype of interactions we see …

Sam Zeller, NO-VE Workshop, 02/07/06 11

Quasi-Elastic Scattering

Why important?

n → - p• QE necessary to accurately predict signal rates in oscillation experiments (including our own)

* e QE are main signal for e appearance searches; have similar kinematics &

• channel used as “golden mode” to normalize other cross section samples - lots of events, well known

(common practice that we will also adopt for now)

Sam Zeller, NO-VE Workshop, 02/07/06 12

Quasi-Elastic Scattering

• highest statistics ~2500 events

• low E data on D2

n → - p

Sam Zeller, NO-VE Workshop, 02/07/06 13

Quasi-Elastic Scattering n → - p

• new information already coming in (NOMAD, 12C)

(R. Petti, NuInt05)

Sam Zeller, NO-VE Workshop, 02/07/06 14

Quasi-Elastic Scattering n → - p

• MiniBooNE:

- 12C (valuable for osc exps)

- this analysis: 60k events (3.2x1020 POT) (already more data than all previous exps combined)

- can select 86% pure QE sample

Sam Zeller, NO-VE Workshop, 02/07/06 15

MiniBooNE QE Data

measure visible E and from mostly Čerenkov () + some scintillation light (p)

n → - p

• most copious events at MiniBooNE• also simplest: two body kinematics

(J. Monroe)

forward muons corresponds to

low Q2 …

Sam Zeller, NO-VE Workshop, 02/07/06 16

• to improve data, MC agreement performing shape fits for: (J. Monroe)

- axial form factor (MA) & - nuclear model pars (EB,pF)

• incorporating new nuclear models (R. Tayloe)

(that are constrained by modern electron scattering data)

MiniBooNE QE Data• similar effect seen by K2K

• working on understanding these features in our data …

Q2 = m2 - 2E(E-pcos)

Sam Zeller, NO-VE Workshop, 02/07/06 17

MiniBooNE QE Data

2MpE – m2

EQE =

2(Mp-E+pcos)

(J. Monroe)

• energy distribution that will be used for CC +/QE cross section measurement

• next, numerator (CC +) …

• making use of E, …

Sam Zeller, NO-VE Workshop, 02/07/06 18

• forward emitted • low Q2

CC 1+ Productioncoherent + productionresonant + production (dominant)

A A+

Sam Zeller, NO-VE Workshop, 02/07/06 19

CC 1+ Productioncoherent + productionresonant + production (dominant)

Sam Zeller, NO-VE Workshop, 02/07/06 20

(K2K, hep-ex/0506008)

• K2K: 1st search for coh + prod at low E• somewhat surprising results …• see no evidence for coh + production!

CC 1+ Productioncoherent + productionresonant + production (dominant)

Sam Zeller, NO-VE Workshop, 02/07/06 21

• forward emitted • low Q2

CC 1+ Production

• MiniBooNE:- inclusive measurement, CH2

- this analysis: 40k events (3.2x1020 POT) (5x more than previous bubble chamber data combined)

coherent + productionresonant + production (dominant)

A A+

Sam Zeller, NO-VE Workshop, 02/07/06 22

CC + Production

Why important?

• poses largest background to QE samples (large & + can be absorbed in nucleus)

• useful for understanding production in CH2 ( → N a background to → e search)

• possibility for CC + oscillation search

• useful in understanding our event reconstruction

N → N +

Sam Zeller, NO-VE Workshop, 02/07/06 23

MiniBooNE CC + Selection• very simple selection:

- events with 2 decay electrons - unique, results in 84% purity

-

e-

e+

+ +

e

(M. Wascko)

=2070 ±16 ns = 2242 ± 17 ns

+e+

• expect to have shorter lifetime from capture (8% in12C)

- will also make use of this later

Sam Zeller, NO-VE Workshop, 02/07/06 24

MiniBooNE CC + Reconstructionmeasure Čerenkov light frommuon (to avoid light from +)

(M. Wascko)

seelarger

deficit inforward (low Q2)than in

QE data

Sam Zeller, NO-VE Workshop, 02/07/06 25

MiniBooNE CC + Data

(M. Wascko)

2MpE – m2 + (m

2-Mp2)

“EQE” =

2(Mp-E+pcos)

• use 2 body (QE) kinematics

• assume in final state (instead of p in QE case)

• energy distribution that will be used for CC +/QE cross section measurement

Sam Zeller, NO-VE Workshop, 02/07/06 26

MiniBooNE CC +/QE Ratio• efficiency corrected CC +/QE ratio meas on CH2

• eff corrections from MC

• ample statistics can perform a binned measurement

(J. Monroe, M. Wascko)

first measurement of thiscross section ratio on a

nuclear target at low energy!

• current systematics estimate:

- light propagation in oil: ~20% - cross sections: ~15% - energy scale: ~10% - statistics: ~5%

Sam Zeller, NO-VE Workshop, 02/07/06 27

MiniBooNE CC + Cross Section• multiplying measured CC +/QE ratio by QE prediction (QE with MA=1.03 GeV, BBA non-dipole vector form factors)

(J. Monroe, M. Wascko)

• ~25% lower than prediction, but within errors

• MC error band from external data constraints

Sam Zeller, NO-VE Workshop, 02/07/06 28

Plausible Interpretation• since MiniBooNE 1st meas on nuclear target at these E’s

• at 1st glance, one might think this is pointing to a potential problem with nuclear corrs

Sam Zeller, NO-VE Workshop, 02/07/06 29

Plausible Interpretation• since MiniBooNE 1st meas on nuclear target at these E’s

• at 1st glance, one might think this is pointing to a potential problem with nuclear corrs

• MiniBooNE results more consistent with ANL than BNL - new data helping to decide between 2 disparate meas - once final, type of info that can feed back into open source MC

• but free nucleon ’s disagree!

BNL

ANL• MC prediction splits difference

Sam Zeller, NO-VE Workshop, 02/07/06 30

New Directions at MiniBooNE

• new antineutrino data!

• observing events from NuMI

• coming soon: new fine-grained new detector to this beamline (comparisons to MiniBooNEwill be interesting)

Sam Zeller, NO-VE Workshop, 02/07/06 31

MiniBooNE Antineutrino Running

1st MiniBooNE antineutrino event

• goals are two-fold:

- check LSND → e signal (longer program)

- measure cross sections - systematic check of analyses - low Q2 investigations - coherent production

• just started antineutrino running (January 19th)

- ~1,000 events/week - will have world’s largest low E data set in a few weeks!

Sam Zeller, NO-VE Workshop, 02/07/06 32

Need for Measurements

• data even less abundant

• provide valuable input for future CP violation searches

P(→ e) ≠ P( → e)

• prefer not to rely on extrapolation of models into regions where no data

• MiniBooNE will make world’s 1st meas of in this E range

- expect ~10k QE in 1 year (after cuts)

Sam Zeller, NO-VE Workshop, 02/07/06 33

Added Difficulty with Beams• contending with “wrong sign” backgrounds ( in beam) - MiniBooNE beam is no exception …

• in neutrino mode, antineutrinos are ~2% of total events

Sam Zeller, NO-VE Workshop, 02/07/06 34

Added Difficulty with Beams• contending with “wrong sign” backgrounds ( in beam) - MiniBooNE beam is no exception …

• need a way to constrain backgrounds in data

• Čerenkov detectors cannot distinguish , + event-by-event (no magnetic field)

• in antineutrino mode, neutrinos are ~30% of total events

“ -enhanced beam”

Sam Zeller, NO-VE Workshop, 02/07/06 35

Constraining Backgrounds in Data

• needed to be more clever

• developed several novel techniques to measure from data

• 1st and most powerful …

• makes use of fact that QE & have different angular distributions

• large angle QE’s as means of measuring content in data

(“poor man’s sign-selection”)

Sam Zeller, NO-VE Workshop, 02/07/06 36

1. QE angular distributions provide best “wrong-sign” constraint, but also … 7% constraint

2. add’l constraint from CC + events in mode data (come entirely from interactions as ’s produce a _ in final state)

- higher E constraint 15% constraint

3. also muon lifetimes ( vs. + to distinguish vs. )- and + have different lifetimes due to capture probability in oil

- not as precise a constraint, but indep of kinematics & recon

30% constraint

→ allows precise antineutrino measurements (once have a handle on backgrounds)

redu

ndan

t ch

ecks

Three Independent Constraints

Sam Zeller, NO-VE Workshop, 02/07/06 37

Antineutrino Measurements• can add new info by mere fact that scattering is different

ddQ2

QE QE

different shape & axialcontribution

difference isolates interference term - directly to axial FF

Sam Zeller, NO-VE Workshop, 02/07/06 38

Antineutrino Measurements• can add new info by mere fact that scattering is different

NC 0 NC 0

• 20% is coherent production • 40% is coherent production• “enhanced” coherent sample

latest K2K results say this peak will be

missing:very apparent in data

Sam Zeller, NO-VE Workshop, 02/07/06 39

Can Detect ’s from NuMI !

NuMI events in MiniBooNE detector

(A. Aquilar-Arevalo)

• ~10,000 events so far

• 100’s of e events (calibration)

• also opened up possibility to use this sample for meas (slightly diff beam spectrum)- MINOS also sees MiniBooNE neutrinos in their detector

• neighbor’s beam

• first off-axis neutrino beam!

Sam Zeller, NO-VE Workshop, 02/07/06 40

SciBooNE (E954)

• new Int’l collaboration

- couple well-understood, fine-grained detector with high rate beam

- unique, low risk opportunity

Sam Zeller, NO-VE Workshop, 02/07/06 41

SciBooNE (E954)

• new Int’l collaboration

- excellent final state resolution - improve on MiniBooNE studies

- couple well-understood, fine-grained detector with high rate beam

- unique, low risk opportunity

Sam Zeller, NO-VE Workshop, 02/07/06 42

SciBooNE (E954)

• new Int’l collaboration

- measurements for T2K

• just received Stage 1 approval (Dec ‘05) rapid schedule: begin data taking this Fall

• www-sciboone.fnal.gov

- excellent final state resolution - improve on MiniBooNE studies

- couple well-understood, fine-grained detector with high rate beam

- unique, low risk opportunity

Sam Zeller, NO-VE Workshop, 02/07/06 43

Conclusions

• coming soon …

- CC QE cross section results - NC 0 cross sections

flux

crosssections

• collected > 700k neutrino (> 1k antineutrino) events (7 x 1020 POT)

- amassed the world’s largest sample in 1 GeV range

- already an order of magnitude more data than previous bubble chamber based measurements

- part of effort to help improve our current understanding of low E

- 1st results on MiniBooNE CC +/QE cross section

• stay tuned for e oscillation results

- HARP results (8 GeV, Be, thick target)