Particle Physics:

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Particle Physics Stability of Matter
Yuri Kamyshkov E-mail kamyshkov_at_utk.edu
Wednesday, June 9, 2004
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Discovery of XX century antimatter
in 1927 P.A.M. Dirac predicted positron from
unifying Einsteins special
relativity with quantum mechanics in 1932 C.D.
Anderson discovered positrons in cosmic radiation

Annihilation e e? ? 2? or 3?
Further discoveries of antimatter in 1955 (O.
Chamberlain, E. Segrè _at_ LBL) anti-proton in
1956 (B. Cork et al. _at_ LBL) anti-neutron in
1965 (D. Dorfan et al. _at_ AGS Brookhaven)
anti-deuterium
p and n are commonly called nucleons anti-p
anti-n anti-nucleons
? How would nucleon and anti-nucleon annihilate ?

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Nucleon anti-nucleon annihilate mostly into
pions. Average number of pions 5
What is electric charge of anti-proton?
What seems to be wrong with this picture ?
Antiproton annihilation in hydrogen bubble chamber
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If ee? and pp annihilate, why e? and p do not
?
i.e. why hydrogen atom is stable and there is no
1H (e?p) ? 2 ? ? or why doesnt proton decay p
? e ? ?
Nucleons (p, n) and other heavy particles are
called Baryons Electron, neutrinos, and other
particles with similar properties are called
Leptons
Stability of the matter (at the level observed so
far) can be explained as a conservation of the
global quantum numbers called baryon charge and
lepton charge.
Why baryon charge is concerved? H. Weyl (1929),
E. Stueckelberg (1938), E. Wigner
(1949) independently tried to postulate the
conservation of nucleon (baryon) charge by
analogy with conservation of electric charge.
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? What is the age of Universe ?
15 Billion years or 1.5?1010 years
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How do we know that baryonic photons do not
exist?
(Lee Yang, Pati Salam, Okun, Sakharov)
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Why Baryon number is conserved?
Conservation of other global quantum numbers
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Matter and Forces (Standard Model)
Matter
Forces
? - photon, electromagnetic (R?2) W,Z -
bosons, weak g - gluon (colored), strong G
- graviton, gravity (R?2)
Scalars
H - Higgs boson ? (not yet
discovered) responsible for particle
masses
Standard Model of Particle Physics has
SU(3)C?SU(2)L?U(1)Y symmetry It is spontaneously
broken at low-energy scale into e-m, weak, and
strong interactions (? 17 parameters to be
defined by experiments)
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Spin hierarchy
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Some terminology
Leptons electron, positron, neutrino,
anti-neutrino (3 families) Quarks do not exist
as free objects, only inside hadrons Hadrons
Baryons and Mesons Baryons objects made of 3
quarks ( qqq ) Mesons objects made of quark and
anti-quarks ( qq ) Pentaquarks recently ? (
qqqqq )
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Few questions
What atom is it?
What are protons made of?
Answer Protons are made of two up quarks and
one down quark uud
What are electrons made of?
Answer Electrons (leptons) are fundamental, as
far as we know
What are baryons made of?
Answer They are made of three quarks put
together. Proton and neutrons are baryons
What are mesons made of?
Answer They are made of quark and antiquark
Answer 4He
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? - decay
electron capture
BTW ? If neutrons decay, why nuclei (12C 6 p
6 n) are stable?
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What tells us that baryon number is NOT
conserved?
No Antimatter in the Universe Baryon Asymmetry
of the Universe (BAU)
? No anti-matter in the Solar system ? In
cosmic rays the ratio of anti-p/p is 10?4 ?
Extragalactic ??ray spectra show no evidence for
anti-matter ? CMBR spectrum is inconsistent
with existence of anti-matter domains in
the universe

• Universe was created from the symmetric
  matter-antimatter state (inflation).
• Three ingredients needed for BAU explanation ( A.
  Sakharov, 1967)
• Baryon number violation
• C and CP symmetry violation
• (3) Departure from thermal equilibrium

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Contribution of all known particles can be
accurately accounted
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Running coupling constants
not measured at very high energies
Strong coupling constant vs ?p
?
measurements
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Standard Model
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Go search PDK in experiments!
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Several large-mass experiments searched for
proton decay
Super KamiokaNDE Kamioka - mine in Japan NDE -
Nucleon Decay Experiment
Super-Kamiokande water-Cherenkov detector
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Location of Kamioka Laboratory
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Super-K detector
50,000 ton of H2O
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PDK search in Super-K
Multiple ring event. This event was one of the
close candidates for proton decay into positron
and pi zero. Pi zero would decay immediately
into two gammas which make overlapping fuzzy
rings. Positron and pi zero would fly in
opposite directions. This is a real event (not
Monte Carlo) recorded on 1997-09-24 120248. It
was found by Brett Viren, but it did not pass
analysis cuts. Time color scale spans 80 ns.
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Decay time
In large detector 1000 t 1kt 109 g detector
(H2O) of nucleons 109?6 ?1023 6 ?1032 of
protons 6 ?1032 ?10/18 3.33 ?1032 if one
proton decays per year 1 3.33 ?1032
/?p(years) ? ?p 3.33 ?1032 years
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What if zero events are observed?
For example, in Super-K N0 ? t 3 yr ? 22 kt
66 kton-yr ?p (N0 ? t )/Nobs ?p gt 66 ?
1.45?1032 yr 9.5 ?1033 yr
(90 CL) Experimental
result ?p (p?e?0) 52 kt-yr gt 3.3?1033
yr (it is less than calculated above due
to reconstruction efficiency and
background suppression)
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Results of gt 20 years of nucleon decay
searches by Kamiokande, IMB, Super-K, Frejus,
Soudan-2 No nucleon decay found!
Impressive limits reached (S-K)
BAU does not tell us a priori the modes of
nucleon decay. Theoretical models can
predict particular nucleon decay modes.
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Proton Decayby David Halliday A proton once
said, "I'll fulfillMy long-term belief in free
will.Though theorists (may) sayThat I ought to
decayI'm damned if I think that I will."
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New idea (gt20 years old) Super Symmetry
Symmetry fermions ? bozons
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Unification of Forces and SUSY
SUSY
GUT
To confirm these ideas one should either discover
super-symmetric particles or observe the proton
decay. Although very attractive theoretically
and supporting each other, so far these ideas
are not confirmed experimentally !
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Plans for constructing larger detectors for
?(B?L)0 mode searches
Further searches for PDK will be limited by
background!
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Did we explore all the possibilities? What we
understood about nucleon lifetime?
Is it the proton lifetime?
Particle Data Group
Mode-independent limit for nucleon lifetime is
only gt 1.6?1025 years !
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PDG 2000
Most of measured modes have lifetime gt n?1030
years but few exceptions
?
?
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Neutron disappearance is a key to
mode-independent nucleon lifetime limit
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(B?L) number
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Question show that for p?e?0 decay ?(BL)0
Question show that in n???? transition
?(BL)?2
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Proton decay is strongly suppressed in this
model, but nR??R and nR?nR are not since nR has
no gauge charges
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How (B?L)?0 processes can be searched in KamLAND
?
KamLAND schematic
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Ikenoyama mnt. Underground layout
of KamLAND in Kamioka mine
KamLAND
Super-K
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KamLAND Collaboration
Sendai, Japan 2003
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1325 advanced photodetectors Hamamatsu R7250 dia.
17 PMTs 554 reused 20 PMTs from old
Kamiokande detector
Time resolution
Detection of single photons with 20 efficiency
R7250
?1s.p.e.
?2s.p.e.
Anode charge ?
?0
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34 of inner area covered with photocathode
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Liquid scintillator mixing/purification plant
Liquid scintillator in KamLAND 80 mineral oil
20 pseudocumene 1.54 g/L PPO Efficiency
70 of anthracene ? detected signal 285 s.p.e.
per MeV (17 only) Cleanliness and high purity
of all construction materials! Several hundreds
materials were radio assayed. Following
purification techniques developed in Borexino
removal of U and Th traces from LS
below analytically detectable level of 10?15 g/g
Initial Goal Measured U lt10?14
(3.5?0.5)?10?18 g/g Th lt10?14
(5.2?0.8)?10?17 g/g K lt10?15 lt 2.7?10?16
g/g
We work on further purification of LS
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Unique features of KamLAND detector
? Large mass 1,000 ton of Liquid Scintillator (
CH2) ? Low detection threshold lt 1 MeV ?
Good energy resolution ? Position
reconstruction accuracy in x,y,z 20 cm ? Low
background 2700 mwe buffer shield
veto-shield Rn shield LS purification for
U, Th lt 10?16 g/g
These features allow observation of the sequence
of nuclear de-excitation states produces by
disappearance of nucleon.
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Signatures of Neutron Disappearance in Large
Underground Detectors E. Kolbe and Yu. K., PRD
67 (2003) 076007
in KamLAND CH2 Liquid Scintillator
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Two-cascade statistical model. SMOKER code J.J.
Cowan, F.-K. Thielemann, J.W. Truran, Phys. Rep.
208 (1991) 267
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(example 11C)
s½ n-hole
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