Neutrino Interaction Physics Mainly Higher Energy Superbeam Studies

1
Neutrino Interaction Physics (Mainly Higher
Energy) Superbeam Studies

• H. Gallagher
• Nu Superbeams Meeting
• May 2004, FNAL

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Outline

• Physics Topics
• Coherent Scattering
• Generalized Parton Distributions (GPDs)
• High-x DIS
• PCAC Studies
• Nuclear Physics
• Pentaquarks
• Beam Comparisons (work to be done)
• BNL/FNAL SB / nFactory
• Outline for Document

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Physics Studies

• Much of the higher energy physics studies are
  based upon recent work done for the Minerva
  proposal, update, and PAC presentations.
• A full evaluation of the systematic errors of
  most of the Minerva measurements has not been
  done, so it is not obvious when they hit their
  systematic limits ? some are beam related, others
  not.
• Broadly speaking, two kinds of measurements
• Good statistics in Minerva (one example -
  coherent production)
• Limited statistics in Minerva (GPDs, high-x PDFs,
  pentaquarks, PCAC studies) ? emphasis here

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Coherent Pion Production
Studies piggyback of Minerva work. Expect 25k
events with an 30 signal efficiency.
Minerva-quality detector can fairly cleanly
measure the CC and NC channels.
PCAC prediction starting from Adlers relation
(q20). Assumptions about the q2 dependence, and
the treatment of the pion-nucleus
scattering. Other calculations based on VMD
treatment. Characterized by a small energy
transfer to the nucleus, forward going p.
MINERnA
Sam Zeller
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Expected MINERnA Results - Coherent p Production
Two models are currently at our disposal the
Rein-Seghal model (NEUGEN/NUANCE) and the
Paschos-Kartavtsev model. Compare kinematic
distributions from each in some of the
important variables one would measure.
A-dependence x and t distributions A few plots
showing expected Minerva and superbeam results
vs. the 2 models. ? separation of diffractive
and coherent contributions on the basis of
t-dependence.
Rein-Seghal
Paschos- Kartavtsev
MINERnA 25 K CC / 12.5 K NC events off C 8.3 K
CC/ 4.2 K NC off Fe and Pb
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Generalized Parton Distributions
Standard parton distributions are only sensitive
to the longitudinal component of the parton
momentum ? insensitive to transverse component
and quark and gluon orbital angular momentum.
GPDs include off-forwardness to x,Q2
Resolving the nucleon spin puzzle.
Currently a major area of research at the
Jefferson Lab, HERMES, Provide unique
combinations of GPDs, not accessible in electron
scattering (e.g. C-odd, or valence-only GPDs), to
map out a precise 3-dimensional image of the
nucleon. MINERnA would expect a few K signature
events in 4 years.
Accessed via weak DVCS processes like
m-
n
g
Eg gt 1 GeV Q2 gt 1 GeV2 W gt 2 GeV t small
W
p
D
p
p
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High-xBj Parton Distribution Functions

• The particular case of what is happening at high-
  xBj is currently a bit of controversial with
  indications that current global results are not
  correct
• Drell-Yan production results ( E-866) may
  indicate that high-xBj (valence) quarks
  OVERESTIMATED.
• A Jlab analysis of Jlab and SLAC high x DIS
  indicate high-xBj quarks UNDERESTIMATED
• CTEQ / MINERnA working group to investigate high
  - xBj region.
• MINERnA will have over 1.2 M DIS events to study
  high - xBj Close examination of the non-PQCD and
  pQCD transition region, in context of
  quark-hadron duality, with axial-vector probe.

Measured / CTEQ6
Might be d/u ratio
SLAC points
CTEQ6
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PCAC Studies
Q2 distribution for SciBar detector
Problem has existed for over two years
All known nuclear effects taken into
account Pauli suppression, Fermi Motion, Final
State Interactions Nuclear shadowing? In VMD
based models, expect to see shadowing at low x,
high Q2. This would be shadowing at high x,
low Q2!
Larger than expected rollover at low Q2
MiniBooNE From J. Raaf (NOON04)
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PCAC Studies / Shadowing
Topic of much discussion at NuINT04, current
theoretical and experimental work. One
promising explanation has actually been around
for some time PCAC and Early Onset of
Neutrino Shadowing Boris Kopeliovich Lc 2n
/ (mp2 Q2) RA (not mA2) Lc 100 times
shorter with mp allowing low n-low Q2
shadowing Miracle 1 is that although neutrino
radiation of a pion is not allowed, the sum of
the allowable fluctuations (a1, a3, rp)
altogether act like a single pion. Coherence
length for an axial probe is 100 times longer
than a vector probe at low Q2 due to PCAC.
Study of Q2, n dependence of shadowing, and V-A
interference terms allows one to study the
dynamics of PCAC and the hadronic structure of
the weak probe.
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Strange and Charm Particle Production
Existing Strange Particle Production Gargamelle-PS
- 15 L events. FNAL - 100 events ZGS - 7
events BNL - 8 events Larger NOMAD
inclusive sample expected

• Theory Initial attempts at a predictive
  phenomenology stalled in the 70s due to lack of
  constraining data.
• MINERvA will focus on exclusive channel strange
  particle production - fully reconstructed events
  (small fraction of total events) but still.
• Important for background calculations of nucleon
  decay experiments
• With extended n running could study single
  hyperon production to greatly extend form factor
  analyses
• New measurements of charm production near
  threshold which will improve the determination of
  the charm-quark effective mass.

MINERnA Exclusive States 100x earlier samples 3
tons and 4 years DS 0 m- K L0 10.5 K m- p0
K L0 9.5 K m- p K0 L0 6.5 K m- K- K
p 5.0 K m- K0 K p0 p 1.5 K DS 1 m-
K p 16.0 K m- K0 p 2.5 K m- p K0n 2.0
K DS 0 - Neutral Current n K L0 3.5 K n K0
L0 1.0 K n K0 L0 3.0 K
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Pentaquarks

• Very preliminary comments based on e-mail
  exchanges between W.A. Mann and Frank Close.
• hep-ex/0309042 shows the evidence for neutrino
  pentaquark production in a combined data set from
  several bubble chamber experiments.
• Experimental signature is resonance in Ks p
• (n) N ? m KSp X and Ks? pp-
• Detectors with good timing open up
• more channels for detection.

hep-ex/0309042
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Pentaquarks
(George Fleming, W.A. Mann, Frank Close)
Excess of 25.6 in 90k CC events. Production
increases with A. Some reasons why neutrino
production would be interesting (Frank
Close) At low Q2, PCAC tells us that the weak
current looks like a p field K field for the
case of Cabibbo-suppressed reactions.
Cabibbo-suppressed reactions directly excite
strangeness 1 or -1 states, no
strangeness ambiguity, and directly excite
resonances. One of the only things we know about
Q is that it couples to KN. (KN accessible in
n production) Measuring pentaquark form
factors (Q2 dependence) to learn about
pentaquark dynamics.
hep-ex/0309042
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Nuclear Physics
A high-intensity neutrino beam offers new
possibilities for the study of nucleon and
nuclear structure. e.g. NuMI has very similar
kinematic coverage to current generation of JLab
experiments. A new window on many of the
questions currently being explored in JLab
experiments.
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Event Rates

• Units of 1020
• Year total POT LE ME HE LEB MEB
  HEB
• 2006 3.0 3.0
• 4.0 3.0 0.7 0.3
• 4.0
  2.5 1.0 0.5
• 4.0 1.0 0.5 0.5 0.5
  0.5 1.0
• TOTAL 15.0 7.0 1.2 0.8 3.0
  1.5 1.5

• LE-configuration Events- (Em gt0.35 GeV) Epeak
  3.0 GeV, ltEngt 10.2 GeV, rate 80 K events/ton
  - 1020 pot
• ME-configuration Events- Epeak 6.0 GeV,
  ltEngt 8.0 GeV, rate 160 K events/ton - 1020
  pot
• HE-configuration Events- Epeak 9.0 GeV,
  ltEngt 12.0 GeV, rate 260 K events/ton - 1020
  pot

nm Event Rates per ton Process CC
NC Quasi-elastic 103 K 42 K Resonance 196 K
70 K Transition 210 K 65 K DIS 420
K 125 K Coherent 8.4 K 4.2 K TOTAL 940 K 288
K
Typical Fiducial Volume 3 tons CH, 1 ton Fe
and 1 ton Pb
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MINERnA Statistics
Assume 9x1020 POT 7.0x1020 in LE n beam,
1.2x1020 in sME n beam and 0.8x1020 in sHE n beam
Typical Fiducial Volume 3-5 tons CH, 0.6 ton
C, 1 ton Fe and 1 ton Pb 3 - 4.5 M events
in CH 0.5 M events in C 1 M events in Fe 1 M
events in Pb
nm Event Rates per fiducial ton Process CC
NC Quasi-elastic 103 K 42 K Resonance 196 K
70 K Transition 210 K 65 K DIS 420
K 125 K Coherent 8.4 K 4.2 K TOTAL 940 K 305 K

• Main Physics Topics with Expected Produced
  Statistics
• Quasi-elastic - nn --gt m-p - 300 K events off
  3 tons CH
• Resonance Production - e.g. nN ---gt n /m-D 600
  K total, 450K 1p
• Coherent Pion Production - nA --gt n /m-A p,
  25 K CC / 12.5 K NC
• Nuclear Effects - C 0.6M events, Fe 1M and Pb
  1 M
• sT and Structure Functions - 2.8 M total /1.2 M
  DIS events
• Strange and Charm Particle Production - (gt 60 K
  fully reconstructed events)
• Generalized Parton Distributions - (few K
  events?)

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Detectors

• I think that the from the point of view of
  neutrino interaction physics, the most productive
  upgrade from Minerva is not necessarily
  superbeams but superdetectors.
• Hydrogen / deuterium targets make many of the
  DIS, nuclear physics studies much more
  straightforward and allow measurement of form
  factors down to Q2 ?0.
• Polarized targets (in conjunction with collimated
  beams) opens up a whole new field of neutrino
  spin physics, allowing clean measurement of the
  flavor separated spin structure functions.

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Beam Comparisons

• Working on a table of event rates for the various
  options

Experimental opportunity
Minerva, FNAL SB, BNL SB, n Factory
Physics topics Form factor measurements(QEL,
resonance) Coherent measurements DIS (kinematic
regions) Duality region GPDs Pentaquarks PCAC
region
Illuminates Statistical power Tradeoff between
low E / high E measurements
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Outline / Plan

• Assume optimum choice of detector(s) for a
  particular beam.
• Event rate table quantify comparisons
• Kinematic distributions from different beams
• Discussion of areas where advances on Minerva /
  miniBoone are statistical (quantify improvements
  in studies of coherent scattering as an example).
• Discussion of new opportunities with superbeams.
• Discuss sensitivity to neutrino interaction
  physics uncertainties as a function of event rate
  for oscillation studies (easiest for Ue3
  measurements).
• Brief discussion of new opportunities with n
  factories,
• polarized targets and spin studies.