Classical picture: rotation of the something Introduction to Spin Physics mass charge One of three intrinsic characteristics of elementary particle 2015October KEK H.Iinuma spin Spin indicates “elementary particle is a small magnet”, like a rotating finite small charged particle which behaves as tiny stick.

How tiny the smallest unit of spin (angular momentum)? m=1[g], r=10[mm] v=63[mm/s] F=1Hz  =2  m=6  [kg] r=6.4  10 6 [m] v=465 [m/s] F=1/24H  =2  /24H 1 F=7.3  Hz Classical electron radius and mass

Let’s see a macroscopic example of spin SPIN is best illustrated by contrasting intrinsic magnetic moment with classical rotation of charged particle. Although this picture is NOT strictly accurate, How about mass-less and neutral charge particles… photon and neutrino?

Mass: m e Charge: e Spin: Magnetic moment S N Total magnetic moment Outermost electron act as small magnet Fe atom MRI Magnetic moment vector (spin vector) rotates in the magnetic field! Protons and neutrons in nuclei act as small rotating, spinning magnets. The Nobel Prize in Physics 1944, 1952 and in Chemistry 1991, etc.

Proton, neutron Electro- magnetic force Spin 1/2 Strong force Weak force electron Atom quark MRI Boson Spin: Integer Carry forces Higgs Spin 0 Fermion Spin: half integer Form materials Our world is composed from Boson and Fermion

Half integer spin? Apply rotation z-axis Pauli exclusion principle Boson Fermion m =0 : Higgs m=1: , g, Z, W m=1/2 q, e,, p, n,…. Spin–statistics theorem In quantum mechanics, a wave function describes the quantum state “m” of an isolated system of one or more particles.

More on Boson A good example: Photon acts as if it has non-zero mass in superconductor condensation of cooper pair into a boson-like state Boson should be mass-less particle. Q1) Why Z and W are huge mass? Q2) why Higgs’ spin=0 ? e-e- e-e- Higgs field can be understand analogy of “cooper pair state”. As photon become massive in the superconductor, Z and W can be massive in the Higgs field! This requires Higgs’ Spin=0 Cooper-pair Spin=0 Higgs field Resistance

Let’s move to familiar particle Proton spin=1/2 Quarks spin=1/2 Do we understand proton perfectly?

How do the quarks carry the spin of protons? proton Proton’s mass, charge and magnetic moment are described in naïve “constituent quark”. Roughly m p /3 each constituent quark Good consistency with experimental results Electron and neutrino beams Proton momentum= gluonquark Momentum sum rule is OK. Spin ½= quark Sum rule is also applicable to spin? Only 25%  gluon +? Later 1980’s Spin puzzle was raised up!

RHIC in Brookhaven National Laboratory 2010/3/2110Hiromi Iinuma Spin ½= gluon +? quark Only 25% We need longitudinally spin polarized spin polarized proton beam  p/p~5%

How to accelerate and keep beam ? To circulate beam in the ring, we use dipole magnet. Normal dipole magnet example poles initially 80% H- source polarization: 80% Many acceleration steps 1.LINAC up to 200MeV 2.Booster up to 1.5 GeV 3.AGS up to 24.3GeV 4.RHIC up to 100GeV There are many difficulty to control beam polarization during acceleration at AGS and RHIC. But Spin also rotates if spin is perpendicular to field

How to achieve high spin polarization? (RIKEN) Flip spin direction every half circle to cancel depolarization process

Measure L-R asymmetry of recoiled particles How to measure beam polarization? We need well measured Physics Asymmetries R L 1.5GeV24.3GeV R L Target (C, p) Recoiled (C, p) polarized proton beam Forward scattered

Ch#1  source for energy calibration 241 Am(5.486 MeV) Ch#2Ch#3 Ch#4Ch#5 Ch#6 Ch#7Ch#8 Ch#9 Ch#10 Ch#11,12 Ch#13 Ch#14Ch#15 Ch#16 ch#1-16 RR ch#1 #16 (Deposit) Energy (MeV) 2010/3/2114 How to measure absolute polarization? R L We use polarized proton target, and measure asymmetry of elastic scattering events. We measure A N precisely. Uncertainty of beam polarization should be the same level of the target polarization! Purity of event selection is the key! P target = 92.4%  1.8%

3.9 M events History of Polarized run  2001: pC polarimeters in RHIC become operational.  2004: pp polarimeter commissioning run. My thesis’ data.  2005~ now : Physics run. pol  p/p % % % % Requirement is achieved!! Absolute polarization PLB 638 (2006), M events PRD (2009) Enough large asymmetry 4~5%. QCD is not applicable. Experimental data is important. We also measure A N precisely.

Physics results from RHIC-Spin 16 Double Spin Asymmetries

Impact on the understanding spin puzzle Very significant constrains from RHIC inclusive pions and jets, Evidence for positive gluon polarization for 0.05< x gluon <0.2 at the level of =0.2 at 10GeV 2 ~ 0.25 ~ 0.2 quark gluon Orbital angular momentum? ? Further good studies are ongoing at RHIC New experiment of polarized e-p collider is planning But I prefer simple particle for the next….

Impact on my life Prof. Saito RHIC-SPIN, my supervisor and the director of J-PARC center Dr. Bunce Leads RHIC-Spin and my mentor Prof. Yamamoto Leading person of superconductive magnet Dr. Fukao  G They lead the way into a new muon spin experiment My son, Age=3 Spin-physics players at Brookhaven National Laboratory

Let’s move to simple spin=1/2 particle space-ventures-risky-for-astronauts-in-future Primary cosmic ray (proton) -- --  e-e- Spin=1/2 Muon:  めそん No Spring Lepton (2 nd generation) charged particle Mass 106MeV/c 2 m   m p /9  m e  200 Lifetime  =2.2[  sec] High transitively Produced in particle accelerators Spin dependent decay  apply to  SR Spin dependent decay emits e + in “  + spin direction”

High Intensity Muon Beam in JAPAN! 20 J-PARC Tokyo KEK 2010/9/28 Bird’s eye photo in Feb P, 30GeV  -beam P, 3GeV Thursday 10:00 Prof. N. Saito Apply MRI technology Fundamental physics Beyond standard model Violation of time reversal What is origin of spin?

spin Measure muon spin oppression frequency and vector Fundamental spin physics at J-PARC

What we can see from precise spin precession? Implicates inner structure of muon? The best precise measurement of Magnetic Dipole Moment Improve sensitivity of Electric Dipole Moment by 200 times! 1mrad (0.006 degree) The world record Phys. Rev. D. 73, (2006) ) MDM 0.46ppm  3  deviates from the SM EDM 0.9  [e.cm] Now, we are aiming (J-PARC NEW exp.) MDM 0.37ppm EDM 1.3  [e.cm] New idea, cutting age technologies

Major R&Ds Ultra cold polarized muon source (2.3keV/c), Muon LINAC up to 300MeV/c, Super precise and compact storage magnet applying MRI technologies  B/B <0.1ppm R=0.33cm J-PARC  -beam How to inject muon beam such a small storage ring? Ultra slow muon microscope Utilize reaction of muonium and benzene Good opportunity to apply muon beam to Material and Life science and industry

Summary  What spin is in elementary particle?  Minimum unit of spin angular momentum  Some familiar examples  Spin–statistics theorem  Spin zero particle (Higgs)  Spin puzzle of proton  Not yet solved…..  Muon spin experiment and future prospects  magnetic dipole moment and electric dipole moment  breaking of time reversal  New muon beam line at J-PARC Material and Life Science Facility We are expecting new research collaboration with material and life science field utilize muon beam!