Pion Physics in the Meson Factory Era R. P. Redwine · 2006-11-27 · Meson Factories The primary...
Transcript of Pion Physics in the Meson Factory Era R. P. Redwine · 2006-11-27 · Meson Factories The primary...
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 11
PionPion Physics in the Meson Factory EraPhysics in the Meson Factory Era
R. P. RedwineR. P. Redwine
Bates Linear Accelerator CenterBates Linear Accelerator CenterLaboratory for Nuclear ScienceLaboratory for Nuclear Science
Department of PhysicsDepartment of PhysicsMassachusetts Institute of TechnologyMassachusetts Institute of Technology
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 22
Meson FactoriesMeson Factories
Los Alamos Meson Physics Facility (LAMPF)Los Alamos Meson Physics Facility (LAMPF)800 800 MeVMeV Proton Proton LinacLinacLos Alamos, New MexicoLos Alamos, New Mexico
Swiss Institute for Nuclear Research (SIN), now Paul Swiss Institute for Nuclear Research (SIN), now Paul ScherrerScherrer Institute (PSI)Institute (PSI)
600 600 MeVMeV Proton Coupled CyclotronsProton Coupled CyclotronsVilligenVilligen, Switzerland, Switzerland
TriTri--Universities Meson Facility (TRIUMF)Universities Meson Facility (TRIUMF)560 560 MeVMeV Proton CyclotronProton CyclotronVancouver, CanadaVancouver, Canada
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 33
Meson FactoriesMeson Factories
The primary goal of the meson factories was to The primary goal of the meson factories was to produce copious quantities of produce copious quantities of pionspions to use in to use in nuclear structure and reaction studies.nuclear structure and reaction studies.Beams of protons, Beams of protons, muonsmuons, and neutrinos were , and neutrinos were also available. also available. Fundamental symmetry tests played a large role Fundamental symmetry tests played a large role at the meson factories (and still do to an at the meson factories (and still do to an extent).extent).I will concentrate on I will concentrate on pionpion--nucleus reactions.nucleus reactions.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 44
Meson FactoriesMeson Factories
LAMPF produced its first beam in 1973.LAMPF produced its first beam in 1973.
SIN and TRIUMF followed very soon after.SIN and TRIUMF followed very soon after.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 55
From Boston, it is equally difficult to get to Los From Boston, it is equally difficult to get to Los Alamos, Vancouver, and Alamos, Vancouver, and VilligenVilligen
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 66
PionsPions
The The pionpion is a spinis a spin--0 boson with 0 boson with isospinisospin 1.1.
It has three charge states (+, 0, It has three charge states (+, 0, --).).
Pi Pi –– nucleon interactions involve singlenucleon interactions involve single--chargecharge--exchange as well as elastic scattering.exchange as well as elastic scattering.
As a boson, the As a boson, the pionpion can be absorbed, although can be absorbed, although absorption on a single nucleon in the nucleus is absorption on a single nucleon in the nucleus is very unlikely.very unlikely.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 77
PionPion nucleus total cross sectionsnucleus total cross sections
Throughout most of the Throughout most of the energy region of interest, the energy region of interest, the Delta (1232) piDelta (1232) pi--nucleon nucleon resonance plays a dominant resonance plays a dominant role.role.The Delta is a spin 3/2, The Delta is a spin 3/2, isospinisospin3/2 resonance with a width of 3/2 resonance with a width of about 120 about 120 MeVMeV..The pi+ is sensitive primarily The pi+ is sensitive primarily to protons, the pito protons, the pi-- to neutrons.to neutrons.The The pionpion--nucleus interaction is nucleus interaction is very strong very strong –– most of the most of the action is on the nuclear action is on the nuclear surface.surface.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 88
PionPion nucleus cross sectionsnucleus cross sections
The Delta resonance The Delta resonance appears strongest in the appears strongest in the absorption channel.absorption channel.
This is still not well This is still not well understood.understood.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 99
Mass dependence of cross sectionsMass dependence of cross sections
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1010
Comparison of proton spectra following Comparison of proton spectra following pionpion and and photon absorptionphoton absorption
220 220 MeVMeV incident incident pionspions(points)(points)
343 343 MeVMeV incident photons incident photons (histogram) (X 55)(histogram) (X 55)
a) 45 dega) 45 degb) 65 degb) 65 degc) 120 degc) 120 deg
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1111
Theoretical ApproachesTheoretical Approaches
Many calculations using multiple scattering to Many calculations using multiple scattering to describe describe pionpion--nucleus interactions.nucleus interactions.
The DeltaThe Delta--hole model explicitly took into account hole model explicitly took into account the fact that the the fact that the pionpion in this energy region was in this energy region was likely to excite a Delta resonance, leaving a hole likely to excite a Delta resonance, leaving a hole in the nucleon states.in the nucleon states.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1212
Elastic ScatteringElastic Scattering
The data are highly The data are highly diffractive in nature.diffractive in nature.
Optical potential Optical potential calculations show strong calculations show strong sensitivity to the radius of sensitivity to the radius of the nucleus.the nucleus.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1313
Delta Delta –– Hole ModelHole Model
The agreement of the DeltaThe agreement of the Delta--hole model with hole model with data is improved if a “Spreading Potential”, data is improved if a “Spreading Potential”, taking into account taking into account pionpion absorption and the absorption and the spinspin--orbit interaction of the Delta, is included.orbit interaction of the Delta, is included.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1414
Delta Delta –– hole model calculations hole model calculations –– with and without with and without the spreading potentialthe spreading potential
pi elastic scattering from 16O at 240 pi elastic scattering from 16O at 240 MeVMeV
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1515
Inclusive pi scattering on 16OInclusive pi scattering on 16O
Solid curve includes medium effects on Delta Solid curve includes medium effects on Delta propagationpropagation
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1616
Inelastic scattering to discrete statesInelastic scattering to discrete states
DWIA calculationsDWIA calculations
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1717
Pi Pi –– Carbon inelastic scatteringCarbon inelastic scattering
Delta Delta –– hole model hole model calculations. calculations. The solid curves include The solid curves include medium effects on the medium effects on the Delta propagator.Delta propagator.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1818
PionPion singlesingle--chargecharge--exchangeexchange
Angular distributions Angular distributions integrated over the integrated over the outgoing outgoing pionpion energyenergyThe lines represent the The lines represent the angular distribution for angular distribution for pipi--nucleon SCXnucleon SCX
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 1919
PionPion SCX to discrete statesSCX to discrete states
LAMPF pi0 spectrometer LAMPF pi0 spectrometer datadataThis is an isobaric This is an isobaric analogue transition.analogue transition.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2020
PionPion Double Charge ExchangeDouble Charge Exchange
This was the first This was the first observation of observation of pionpion DCX DCX to a discrete state.to a discrete state.It also is the largest It also is the largest single pi DCX cross single pi DCX cross section to a discrete state section to a discrete state ever measured!ever measured!The hope for pi DCX was The hope for pi DCX was that it would show great that it would show great sensitivity to twosensitivity to two--nucleon nucleon correlations.correlations.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2121
PionPion Double Charge ExchangeDouble Charge Exchange
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2222
Inclusive Inclusive PionPion DCXDCX
Inclusive data are well Inclusive data are well described by a model described by a model which includes successive which includes successive SCX reactions in SCX reactions in competition with other competition with other important reactions.important reactions.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2323
PionPion DCX on 4HeDCX on 4He
Data at 25 degData at 25 dega) 270 a) 270 MeVMeV pi+pi+b) 240 b) 240 MeVMeV pi+pi+
The curves represent a The curves represent a sequential model of DCX.sequential model of DCX.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2424
PionPion Absorption in NucleiAbsorption in Nuclei
This was a major area of investigation.This was a major area of investigation.
PionPion absorption involves dumping a large absorption involves dumping a large amount of energy in the nucleus.amount of energy in the nucleus.
PionPion absorption was expected to be sensitive to absorption was expected to be sensitive to twotwo--nucleon correlations.nucleon correlations.
The prototype reaction is pi+ d The prototype reaction is pi+ d --> pp.> pp.
The data turned out to be very interesting.The data turned out to be very interesting.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2525
PionPion AbsorptionAbsorption
((pi+,pppi+,pp) reactions on Ni ) reactions on Ni at 165 at 165 MeVMeVThere is a clear indication There is a clear indication for twofor two--nucleon nucleon absorption, but there is absorption, but there is evidence for a lot of cross evidence for a lot of cross section involving more section involving more than two nucleons.than two nucleons.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2626
PionPion absorption on 3Heabsorption on 3He
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2727
PionPion absorption at 160 absorption at 160 MeVMeV
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2828
PionPion Absorption in 4HeAbsorption in 4He
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 2929
What do we know about What do we know about pionpion absorption in nuclei?absorption in nuclei?
It is a major reaction channel.It is a major reaction channel.It resonates more than the other channels.It resonates more than the other channels.TwoTwo--nucleon absorption is important, but so is nucleon absorption is important, but so is multimulti--nucleon.nucleon.There is some evidence for coherent absorption There is some evidence for coherent absorption involving more than two nucleons that may be involving more than two nucleons that may be new physics, but it is not definitive.new physics, but it is not definitive.The breakup into separate channels in 4He is The breakup into separate channels in 4He is hard to understand and may be an important hard to understand and may be an important clue.clue.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3030
SummarySummary
The meson factory era was a rich and exciting The meson factory era was a rich and exciting one, and I have only been able to touch on one, and I have only been able to touch on some important aspects.some important aspects.The special properties of The special properties of pionspions do give one do give one access to some important states and reactions access to some important states and reactions which are not available with other probes.which are not available with other probes.The difficulty in describing precisely the The difficulty in describing precisely the interactions of interactions of pionspions in nuclei ultimately limited in nuclei ultimately limited the utility of the utility of pionspions as a probe of nuclear as a probe of nuclear structure.structure.Understanding the important reactions of Understanding the important reactions of pionspionswith nuclei remains an important challenge.with nuclei remains an important challenge.
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3131
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3232
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3333
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3434
Large Acceptance Detector System (PSI)Large Acceptance Detector System (PSI)
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3535
September 29, 2006September 29, 2006 Bates SymposiumBates Symposium 3636
Delta Delta –– Hole model fits to elastic scattering and Hole model fits to elastic scattering and total cross sectionstotal cross sections