Course in Detectors for Nuclear and Particle Physics

Transcription

Duration: 15 weeks, 3 lecture and 2 tutorial hours per week
Timetable: 10:15 - 12:00, Tuesdays, 10:15-13 Thursdays.
This is a proposals for new hours, I do not want to teach on Fridays.
Please tell me what is best for you !
Objectives: On successful completion of this course, you should:

understand how energetic particles interact with the matter they traverse;
be able to describe qualitatively how energy loss depends on the properties of the traversing particle;
be familiar with methods by which atomic ionisation and excitation are utilised in solid, liquid and
gaseous detectors;
understand coherent effects in matter, and their exploitation in Cherenkov and transition radiation
detectors;
appreciate the advantages and disadvantages of shower detectors or calorimeters;
understand basic design criteria for practical detectors;
recognise appropriate applications for the different types of detectors;
be able to evaluate the performance of various simple detector designs.
Handouts: Handouts are provided for each section of the course, consisting of course notes, with diagrams and
other information. Detailed notes are provided for the more mathematical sections of the material.
Anna Lipniacka
Detectors in N and P physics, L1
The Course WEB page : http//::www.physto.se/~lipniack/detectors/
This page contains a summary of most important information
and links to explanatory material
Course notes and schedule are posted there as well
Introductory course and exercises with real data collected
at CERN- make your own discovery at
http://hands-on-cern.physto.se
Recommended Books:
K. Kleinknecht - Detectors for Particle Radiation, C.U.P. 1990
R.K. Bock & A. Vasilescu - The Particle Detector BriefBook, Springer 1998 Web
version linked on Course Web page
Preliminary planning for the Course content is posted on the web page.
Important: there will be homework problems given. You are expected
to give 45' presentation on chosen detector topics. There might be a trip
to CERN as a part of the course.
Anna Lipniacka
Introductory Lectures Outline
Content of the Standard Model of Particle Physics,
matter and force particles, reminder
What are the detectors for. A quick tour thru a “
for high energy particles
typical “ detector
Marathon thru accelerators and detectors
Exercise: recognizing particles in a detector of LEP.
Disclaimer: this material will be on introductory level, to show
you the end goal of subject. All points will be discussed later
in more detail
Anna Lipniacka
Addendum
"Holy Book" of Particle Physics, with summary of all the particle
properties can be found at http://pdg.lbl.gov . In particular
particle listings (quarks, leptons etc ) from
http://pdg.lbl.gov/2000/contents_tables.html
There is a summer student program each year at CERN. You
have to apply before the end of January 2002.
http://cern.web.cern.ch/CERN/Divisions/PE/HRS/Recruitment/summ.html
Anna Lipniacka
Fundamental Particles and Antiparticles
electron number
muon number
tau number
For each SM particle exists
an antiparticle with the same
spin and mass.
But with OPPOSITE charge,
magnetic moment, and
opposite "family number",
and fermion number
Bosons are their own anti-particles
+
ie, W <-> W , Z<-> Z , γ <−>γ
Anna Lipniacka
Quarks and Hadrons
Antiquarks
have opposite
Colour I3, C,S,T,B,Q
charge colour, quark
number,baryon
blue
green number.
red
blue
Answer:
green
+2, -1
red
have spin 1/2
I3= 1/2
I3= -1/2
C= 1
S = -1
T= 1
B = -1
baryons (qqq) and antibaryons(qqq) can have spins ? (1/2,3/2,5/2 , 7/2 ...)
mesons (qq) can have spins ?
Anna Lipniacka
0,1,2,3 ........
Question: what is the
maximal electric charge
of a baryon? And the minimal?
The Discovery of Quarks,baryon multiplet
Quarks were postulated by Gell-Man to explain regularities of the mass, charge, and
strangness (discovered thanks to long life-time) in observed hadrons:
Question: What are the quarks assignments for baryons below ?
Hypercharge Y=
LB+S+C+B+T
Prove I3=Q-Y/2
S, strangness
ddu
Q=-1/3(Nd+Ns+Nb)+
2/3(Nu+Nc+Nt)
sdd
-1
Y=1/3(Nu+Nd+Ns.+Nc......)
duu
939MeV
sdu
-1/2
-Ns+Nc-Nb+Nt=
1/3Nu+1/3Nd-2/3Ns
+4/3Nc-2/3Nb+4/3Nt
Q-Y/2=2/3Nu-1/6Nu
-1/3Nd-1/6Nd=
1/2Nu-1/2Nd
0
1/2
-1
suu
1
1193 MeV
Find out masses of
these baryons in the
book and estimate
mass of the s quark.
Why masses of
baryons with the
same S are nearly
equal ?
I3=1/2(Nu-Nd)
ssu
ssd
-2
1318 MeV
LB=baryon number Baryons with parity +1 and spin 1/2m(s) close to 200 MeV
Anna Lipniacka
Discovery of Quarks, meson multiplets
S, Strangness=-Ns+Ns- su
-sd
Find quark-antiquark
assingments for mesons
below
- 0 +
π , π, π are the
lightest know mesons,
they have different charges
but nearly the same masses
and same spin-parity
They might be different I3
states of the "same" meson
Find the I of the multiplet.
1
- uu-dd
-1
1
- - uu+dd ud
-ud
-
-
I3=1/2(Nu-Nd-Nu+Nd)
su
-1
sd
Same as for spin
number of states= 2I-1
so I=1 for 3 states
Light, spin=0, Parity=-1 mesons
Anna Lipniacka
Summary of the Standard Model
Remember: three familes of fermions= leptons + quarks
remember lepton and quark electric charges, remember the
order of magnitude of the masses. Remember that fermions have
other charges except of electric-> all fermions have weak charge,
and quarks have colour charge as well.
Remember what are the types of field particles= photon (EM)
W+,W-,Z (weak), gluons (strong,8 types of gluons). Gluons and the
photon have the mass=0, while W,Z are as heavy as 80-90 protons!
Remember what kind of interactions are felt by what kind
of particles: weak by all, strong by quarks and gluons, EM by
particles which have the electric charge.
Anna Lipniacka
How do we detect various particles?
Directly : via their interactions with the matter of our detectors.
At the moment we are able to detect like that particles
which live longer than around 10**{-12} s (or a picosecond)
Indirectly : via their decay products ( if they live long enough, if
not via decay products of their decay products...)
At the end of the chain we expect quasi-stable decay products
which we can recognize in our detectors via their interactions
and measure their moment and/or energies
Directly detectable stable and quasi-stable particles:
e-electron,positron : photon , p,n - proton , neutron
µ ? muons (positive, negative ) , lifetime ~10**{-6} s
π+,π−,Κ+,Κ− . Κ 0 , lifetime ~10 **{-8} s
L
0
Question: what about π 0 and K
?
S
Anna Lipniacka
Side remark: So what is fundamental anyway?
Presently we think that quarks and leptons (matter particles)
and photon, W,Z, gluons (interaction particles) are fundamental,
because we cannot see any structure inside them !
Anna Lipniacka
What does it mean to "see the structure" ?
What does it mean to see an object anyway ?
" with eyes"--> it means to be able to register the light scattered
of an object.
For particle physics it means to be able to register "anything"
scattered of an object.
If projectiles are
too big compared to our object
they will not scatter!
"size of the projectile'=wavelenght (λ) < "size of the object"
Our projectiles are De Breugle waves : wavelength =h/momentum
D
E
T
E
C
T
O
R
We need projectiles of high momentum to see small objects.
Anna Lipniacka
What was LEP, in a nutshell
Large Electron-Positron Collider, 27 km
long, largest accelerator ever built.
Electron and positron beams crossed in LEP
ALEPH
OPAL
12
10 times in 1989-2000 (start and end ).
Energy in Elementary Collisions:
in 1989-1995:
CMS Energy: 91 GeV (mass of Zr nucleus)
in 1995-2000:
CMS Energy 130-208 GeV ( Cs-Pb nuclea)
The energy of electrons exceeded their mass
200 000-400 000 times - like it was
0.1 nsec after the Big Bang.
Four experiments-laboratories: ALEPH,
DELPHI, L3 and OPAL were
recording the collisions.
Anna Lipniacka
L3
DELPHI
DELPHI at LEP, sentimental tour...
L. Eclerck supermarket
helium
tank
construction
hall
construction
hall and labs
nitrogen
tank
Anna Lipniacka, U. of Stockholm
The legacy of LEP, and steps beyond
DELPHI at LEP, at birth time...
Muon
chambers
Hadronic
calorimeter
Electro
magnetic
cal.
Tracking detector,
Time Projection
Chamber
Anna Lipniacka
e+
e-
The DELPHI at LEP Cavern, the detector ( and 1100 km of cables)
are hidden behind the electronics' barracks
DELPHI on line
DELPHI at LEP, obituary, after dismantling
Hadronic
calorimeter
Tracking
detectors
Electro magnetic
calorimeter .
magnet, superconducting
weight 2500 t,
used 890 l of liquid
helium
LEP and Life
ALEPH, DELPHI, L3 and OPAL Collaborations
~1500 physicists in ~150 scientific institutions in Europe,
Americas, Asia, Australia, Africa,
Built four detectors of ~1000 cubic meters each,
New Zealand.
comprising several millions of electronic channels
and spent two million person-hours "baby sitting" them.
analyzed several millions of "events" of electron-positron collisions,
and wrote several millions of lines of programming code
Published more than 1200 papers in refereed
scientific journals, ~400 doctorate theses, ~5000
public scientific (conference) notes
Life of LEP:
First Idea: 1976
Beginning of the construction : 1983
Largest European civil engineering Project in 1983-88
Start data taking : 13 of August 1989
End data taking : November 2000
The data are still being analyzed for
Consumed 0.01% electricity of Europe, less power scientific publications, and in educational
consumption than of a flying Jumbo-Jet
projects
First days of LEP, observing the Z
5 days "pilot run" of LEP. All detectors seen few Zs, even before their trackers were
up, it was clear we observed Z hadronic decays.
e+e- -> µ+ µ−
eMuon chambers
e
+Z
µµ
+
+
e-
µ-
+
e
µ
Hadronic calorimeter
tracking
Electromagnetic
calorimeter
B field
γ
+
What have we seen at LEP1 ?
Observing Z decays:
e+e- -> τ+ τ−
e-
τ-
+
"3 prong"
+
e Z
τ
+
e-
τ-
+
e
τ
"1 prong"
B field
γ
+
e-
q
-q
e+ Z
"broken colour field"
γ
+
e
e +
γ
e+
-
-
We have seen electrons,
muons, taons and quarks
consistent with production of
e- u,d,s, c and notably b quarks.
E
M
C
A
L
e+
e +
+
+ +
e
e+ Z
e-
e-
e
e-
e-
e
e+ e- -> e+e-
No new "observable" particles
lighter than 45 GeV.
What about neutrinos and other
"unobservable" particles ???
B
Charge of strong interactions as a function
of energy.
Vacuum polarization effects make charges dependent
on the distance (energy of our probe). These effects
were hoped to be particularly important for QCD,
quantum field theory of Strong Interactions. They
have to account for STRONG interactions
at low energies (nuclear regime), and apparently
much weaker strong interactions at high energies.
First consistent proof
of running coupling
constant in Quantum
Chromodynamics.
Anti-screening expected due to color-charged
qluons (field carries charge, thus the observed
charge increases with the distance)
color
charge
e - 3-jet
e + E ~Z,γ
1/R
-q
QCD
q
R
(LEP)
strong
charge
LEP1.5, Rb and the Dark Side ( 2)
Soon after LEP switched on for the FIRST TIME to higher energies we saw this event:
Could these be Wino production?
For Wino decays it
0 is more probable that
1 produced charged leptons are of different fla0 vour and go more
1 "back to back".
e+
W
e+
Z/γ
DM particles
W
e-
µ−
beam
0
1
e+
Z/γ
e-
0
e-
e+
1
It could be associated
production of neutral
bosons partners (Zinos,
Higgsinos), which we need
to give 30% of the
0 mass of the Universe
1
as Dark Matter
The Dark Side of the story was, that we did not see any more of these in a while... and Rb came slowly
back to SM value, after understanding better ADLO correlated systematics
Open questions in Particle Physics
The origin of the family structure, the origin of masses and mass hierarchy of
leptons and quarks
The origin of the 4 interactions, do they become 1 interaction at high energy ?
We know that their strength depends on the
energy.
All known Universe is build of matter and there is very little antimatter. We do not
know why it is so matter-antimatter
assymetric.
90% of the mass of the universe is carried by an unknown form
of matter. (Dark Matter and Dark Energy). What is this matter ?
Best candidate, "supersymmetric
particles". Is there
another form of energy in the universe than matter itself?
Dark energy and Cosmological constant?
Are elementary particles we know today really elementary?
Is there another layer of substructure? Try some model building just for fun.
Anna Lipniacka
What comes after LEP ?
The Large Hadron Collider ,
LHC, it will collide protons
with protons, at the
accelerator will be build in
the LEP tunnel. Two of the
major detectors will be
ATLAS and ALICE . We are
involved in ATLAS and
ALICE collaborations here
in Bergen.
ATLAS detector cavern in
summer 2003
Anna Lipniacka
LHC, the brave New World
Proton -Proton collision, 14 TeV CM, 40 MHz beam crossing rate:
Luminosity 10-100 fb
-1
per year/experiment
New Physics:
If below ~4 TeV will be observed
after few years of running.
2007
~
proton-proton
CMS energy in elementary gluon-gluon collisions:
> 1 TeV at 10 -100 Hz
> 3 TeV
at 0.1- 1 Hz
bb rate ~ 0.1 MHz
8-80 millions of tt events per year/experiment
2-20 thousands WH events per year/experiment
Rare Decays:
Example : Br Bs
10 9 SM
will be observable after 2 years
of lower luminosity run.
8
SUSY ( 1 TeV) predicts Bs
10
~
OLD ~115 GeV Higgs boson?
5 σ signal after 1 year of running
50% of sensitivity in h -> γγ