Neutrino Scattering Physics with the Fermilab Proton Driver

Neutrino Scattering Physics with the Fermilab Proton Driver Introductory Overview Conveners: Jorge G. Morfín (Fermilab) Ron Ransome (Rutgers) Rex Tayloe (Indiana)

A bit of history… 1930 -Wolfgang Pauli Dear Radioactive Ladies and Gentlemen…. 2

Milestones in the History of Neutrino Physics 1934 - Enrico Fermi develops a comprehensive theory of radioactive decays, including Pauli's hypothetical particle, which Fermi coins the neutrino (Italian: "little neutral one"). 1959 - Discovery of a particle fitting the expected characteristics of the neutrino is announced by Clyde Cowan and Fred Reines. 1962 - Experiment at Brookhaven National Laboratory discovered a second type of neutrino ( m). 1968 - The first experiment to detect e produced by the Sun's burning (using a liquid Chlorine target deep underground) reports that less than half the expected neutrinos are observed. 1985 - The IMB experiment observes fewer atmospheric m interactions than expected. 1989 - Kamiokande becomes the second experiment to detect e from the Sun finding only about 1/3 the expected rate. 1994 - Kamiokande finds that m travelling the greatest distances from the point of production to the detector exhibit the greatest depletion. 1997 - Super-Kamiokande reports a deficit of cosmic-ray m and solar e, at rates agreeing with earlier experiments. 1998 - The Super-Kamiokande collaboration announces evidence of non-zero neutrino mass at the Neutrino '98 conference. 2000 - First direct evidence for the t announced at Fermilab by DONUT collaboration. 2004 - APS Multi-divisional Neutrino Study. 2005 - Mini. Boo. Ne announces result - yes/no/maybe LSND correct, MINOS starts data-taking. 3

What are the Open Questions in Neutrino Physics From the APS Multi-Divisional Study on the Physics of Neutrinos What are the masses of the neutrinos? What is the pattern of mixing among the different types of neutrinos? Are neutrinos their own antiparticles? Do neutrinos violate the symmetry CP? Are there “sterile” neutrinos? Do neutrinos have unexpected or exotic properties? What can neutrinos tell us about the models of new physics beyond the Standard Model? The answer to almost every one of these questions involves understanding how neutrinos interact with matter! Among the APS study assumptions about the current and future program: “determination of the neutrino reaction and production cross sections required for a precise understanding of neutrino-oscillation physics and the neutrino astronomy of astrophysical and cosmological sources. Our broad and exacting program of neutrino physics is built upon precise knowledge of how neutrinos interact with matter. ” 4

Outline of the Study of Neutrino Scattering Physics What motivates further study of neutrino scattering physics? t t What will we know by the start of a Fermilab Proton Driver (FPD)? t Snapshot of expected experimental results at FPD start-up What can best/only be done with the FPD? t EPP needs - future Wednesday talk NP needs - future Wednesday talk Is there anything left to do and reason to do it? What tools do we need to do it? t t “Designer” beams Specialized detectors 5

What’s actually happening in Neutrino-Nucleus Scattering + A/N/q > /m + H Nucleus/nucleon/quark NC / CC We don’t know incoming neutrino energy. We don’t know, a priori, if it interacts with nucleus, nucleon or quark. For CC event, we infer incoming neutrino energy from measured final-state energy. Since s. T is small (order 10 -(38 -40) cm 2) need intense neutrino beams and/or massive target/detectors. Using a massive target/detectors masks details of the final state including the energy. We need an intense neutrino beam so we can gather significant statistics with a fine-grained, low-A target/detector to see details. 6

In spite of (because of) the experimental challenges, Neutrino Scattering Physics at FPD brings together several communities EPP - motivated by increased understanding of physics relevant to neutrino oscillation experiments, properties of the neutrino and structure of nucleon NP - motivated by understanding of physics complementary to the Jlab program (form factors, structure of nucleon) Neutrinos from 8 Ge. V Protons Limited scope of physics topics Minimize backgrounds from higher energies Specialized study of very low-energy phenomena Neutrinos from 120 Ge. V Protons Extended scope of physics topics to cover quasi-elastic to DIS Must understand/study “backgrounds” Neutrino energies similar to JLab 7

Motivation: EPP - Neutrino Oscillation requirements Future Wednesday talk for details e appearance t needs: Coherent pion cross sections » Robust predictions from CC and NC processes t t t High y m cross sections If signal is seen, we really need QE and resonance cross sections much better than we have now Control neutrino/anti-neutrino systematics at 1 percent level for mass hierarchy and CP studies. High t t t Statistics m disappearance needs: Measurements of Nuclear effects in neutrinos “neutrino energy calibration” Ratio of Quasi-elastic to non-Quasi-elastic cross sections 8

Motivation: Nuclear Physics Interest - Ron Ransome Future Wednesday talk for details Significant overlap with JLab physics for 1 -10 Ge. V neutrinos Four major topics: Nucleon Form Factors - particularly the axial vector FF Duality - transition from resonance to DIS (non-perturbative to perturbative QCD) Parton Distribution Functions - particularly high-x. BJ Generalized Parton Distributions - multi-dimensional description of partons within the nucleon 9

Neutrino Scattering Topics Quasi-elastic Resonance Production - 1 pi Resonance Production - npi, transition region - resonance to DIS Deep-Inelastic Scattering Coherent Pion Production Strange and Charm Particle Production s. T , Structure Functions and PDFs t t s(x) and c(x) High-x parton distribution functions Nuclear Effects Spin-dependent parton distribution functions Generalized Parton Distributions 10

State of our Knowledge at start of FPD - Time Snapshot Assume following experiments complete… K 2 K - 12 Ge. V protons Mini. Boo. NE - 8 Ge. V protons MINER A (Running parasitically to MINOS) - 120 Ge. V protons HARP, BNL E 910, MIPP (E 907) - Associated experiments to help flux determination Jlab - High precision elastic scattering to help QE analysis T 2 K-I (no input as to scattering physics expectations) FINe. SSE 11

Completed experiments by FPD-time Main physics channels: quasi-elastic, resonant and coherent 1 -p production May also have a reasonable n sample of the above channels En (Ge. V) Main physics channels: quasi-elastic, Resonant and coherent 1 -p, and low-W, multi- p channels 12

MINER A MI -120 Ge. V Protons C, Fe and Pb Move target only Nuclear targets n Main Physics Topics with Expected Produced Statistics Quasi-elastic Resonance Production Coherent Pion Production Nuclear Effects DIS and Structure Functions Strange and Charm Particle Production Generalized Parton Distributions 300 K events off 3 tons CH 600 K total, 450 K 1 p 25 K CC / 12. 5 K NC C: 0. 6 M, Fe: 1 M and Pb: 1 M 2. 8 M total /1. 2 M DIS event > 60 K fully reconstructed events few K events 13

(Quasi)-elastic Scattering Dominant reaction up to ~1 Ge. V energy Essential for E measurement in K 2 K/T 2 K The “well-measured” reaction t t Uncertain to “only” 20% or so for neutrinos Worse in important threshold region and for anti-neutrinos (88% purity) Axial form-factor not accessible to electron scattering t Current status Essential to modeling q 2 distribution Recoil proton reconstruction requires fine-grained design - impractical for oscillation detectors Recent work focuses on non-dipole form-factors, non-zero Gn. E measurements Mini. Boo. NE K 2 K Sci. Bar (80% purity) 14

Neutrino Scattering: 8 Ge. V Proton Driver - Rex Tayloe Future Wednesday talk for details - NC elastic scattering - A measurement of NC elastic scattering is sensitive to axial, isoscalar component of proton (strange quark contribution to proton spin, Ds) - Ratio of NC/CC reduces systematics - proton driver would enable this measurement with - and perhaps (with high intensity) measurement on nucleon targets (H/D) allowing elimination of nuclear structure errors. - e elastic scattering - sensitive to magnetic moment => new physics - measured by low-Ee recoil energy behavior - rates are low! Require highest-intensity beam. FINe. SSE could give us a first look at these topics 15

MINER A CC Quasi-Elastic Measurements Fully simulated analysis, including realistic detector simulation and reconstruction Average: eff. = 74 % and purity = 77% Expected Mini. Boo. NE and K 2 K measurements We will understand - nucleus elastic scattering by the time of FPD. Except for possible Mini. Boo. Ne, low E sample, we will NOT have elastic n -nucleus and certainly not n / n - nucleon as well 16

Coherent Pion Production t. Characterized by a small energy transfer to the nucleus, forward going p. NC (p 0 production) significant background for m --> e oscillation search. t. Data has not been precise enough to discriminate between several very different models. p 0 Z P t. K 2 K, with their Sci. Bar detector, and Mini. Boo. NE will attempt to explicitly measure this channel - important low En measurement N N t. Expect 25 K events and roughly (30 -40)% detection efficiency with MINER A. t. Can also study A-dependence with MINER A 17

MINER A: Coherent Pion Production 25 K CC / 12. 5 K NC events off C - 8. 3 K CC/ 4. 2 K NC off Fe and Pb Rein-Seghal Paschos. Kartavtsev We will understand coherent scattering well by the time of FPD. MINER A Expected Mini. Boo. NE and K 2 K measurements Except for a possible Mini. Boo. Ne low E sample, we will NOT have measured - coherent scattering. 18

Parton Distribution Functions CTEQ uncertainties in u and d quark fits 19

DIS: Parton Distribution Functions Ability of n to taste different quarks allows isolation of flavors n/ n - Proton Scattering At high x No messy nuclear corrections! F 2 np - x. F 3 np = 4 xu F 2 np + x. F 3 np = 4 xu EPP and NP interest in PDFs Need n and p/n target 20

Nuclear Effects - studied only with charged leptons S. Kumano Fermi motion 1. 2 EMC NMC E 139 E 665 1. 1 1 valence-quark 0. 9 original 0. 8 shadowing 0. 7 0. 001 0. 01 sea quark antiquark EMC finding x 0. 1 valence quark 1 EXPECTED to be different for n!! 21

Difference between -A and m-A nuclear effects Sergey Kulagin Need significant n statistics to fully understand nuclear effects with the weak current 22

What will we need beyond Mini. Boo. NE, K 2 K and MINER A for neutrino scattering at FPD? HIGH-STATISTICS ANTINEUTRINO EXPOSURE t HYDROGEN AND DEUTERIUM TARGET FOR n and n t Need reasonable event rates at E ≈ 1 GEV NARROW BAND BEAM FOR DETAILED LOOK AT NC t Need to improve purity of n beam? Is off-axis beam sufficiently narrow? IMPROVED DETECTOR TECHNIQUES t t Particularly good neutron detection for n Need a fully-active detector for H 2 and D 2 exposures 23

Need a Very Efficient Beam Low energy Nu. MI ‘n””” ’ beam yields around 1. 1 n events for every n event! Resulting beam is almost pure n beam: in n mode = 4 x 10 -3 Loose factor five in intensity compared to Nu. MI + factor 3. 5 compared to n 24

Need a large H 2/D 2 target An efficient fully-active CCD coupled tracking detector Bubble Chamber A Chicago - Fermilab collaboration developing Contemporary large BC design/construction/operation Techniques including CCD readout H_2/D_2 BC Placed in the upstream part of MINER A 25

Summary At the completion of Mini. Boo. NE, K 2 K and the MINER A parasitic run we will have reasonable results for neutrino-nucleus interactions including exclusive cross-sections, form factors and nuclear effects. We will need the FPD, with both an 8 Ge. V (proton) and 120 Ge. V (proton) neutrino program, to have similarly reasonable results for: t t -nucleus cross-sections, and - proton and neutron (D 2) cross-sections, / - e elastic scattering high-statistics narrow-band studies of NC (and CC) channels. There is considerable work to be done in detailing the neutrino scattering program at the FPD. Your participation is most welcome. 26