The Asymmetry between
Matter and Antimatter
Besma M’charek
FEW, Vrije Universiteit Amsterdam
Outline
• The Standard Model of
Physics and asymmetry
between matter and
antimatter
• Charge Parity (CP)
violation.
• Measuring CP violation
with the LHCb detector
at CERN Geneva.
• Summary.
“Matter /antimatter asymmetry”
The asymmetry between matter
and antimatter
2
Matter/antiMatter
Matter
neutron
Nucleus
The asymmetry between matter
and antimatter
proton
electron
quarks
atom
3
“The Standard Model”
• The fundamental building
block of matter consists of:
6 quarks (u, d, c, s, t, b)
6 leptons (e,μ,τ,νe,νμ,ντ).
• These particles interact
through four difference
forces:
• electromagnetic
• strong forces
• weak forces
• gravity
The asymmetry between matter
and antimatter
4
Where is the antimatter?
The asymmetry between matter
and antimatter
5
Where is the antimatter?
< 1011 sA
1011 s
matter +
antimatter
106 s
300 s
300,000 y
1 billion y
13.7 billion y
H/He
3000K
1st stars
life
EM
EW
The asymmetry between matter
and antimatter
6
Charge Parity symmetry
• Parity symmetry :
• Parity P reflects a system
into its mirror-image
• What if your image behaves
differently than you??
=>In weak
interactions
, parity
symmetry is
always
violated
• Charge symmetry:
• Charge conjugation C changes
the electric charge of the
particle.
• e +  e +
•=>In
K -weak
 Kinteractions,
charge
symmetry is always violated
•Charge Parity symmetry:
•Changes a particle into its
antiparticle.
=>In weak interactions, CP is
almost never violated
The asymmetry between matter
and antimatter
7
Escher on CP violation…
P
C
CP
C
P
The asymmetry between matter
and antimatter
8
Weak interactions
photon
ge
A main difference between
electromagnetic and weak
interactions is in the coupling
Electromagnetic
interactions
u
Weak
interactions
W+
iγ
b gube
constants ge and gubeeiiγ , ..
•
1 for the electromagnetic
•
9 for the weak
 Weak interactions can
change quark flavors ( e.g.:
from up u to bottom b).
 Mixing of quarks
The asymmetry between matter
and antimatter
9
B
B-mesons in the LHCb detector
B-mesons
Two
quarks, one
is always a
b-quark
•B-mesons mix to:
BB
•In the LHCb detector, we want to study
weak interaction with the special B-decays:
Bs  Ds K 
Bs  Ds K 
Bs  Ds K 
Bs  Ds K 
The asymmetry between matter
and antimatter
10
CERN
1989-2000 LEP e+e (88-209 GeV)
2007-2015 LHC pp (14000 GeV)
LHCb
CMS
Atlas
Alicematter
The asymmetry between
and antimatter
11
The LHCb detector

The detector
Results
Simulation and Reconstruction
The asymmetry between matter
and antimatter
12
Summary
•In the universe, there is an asymmetry between
matter and antimatter.
•We need CP-symmetry breaking in order to
explain this asymmetry.
•We will use the LHCb detector and study the
decay of B-mesons (abundant in this detector).
•We will measure the parameter γ
The asymmetry between matter
and antimatter
13
Additional slides!!!
The asymmetry between matter
and antimatter
14
History of our universe
• First the universe was hot and compact: a
soup of energetic photons and massive
particles.
• The laws of physics allow a sufficiently
energetic photon to create a
particle/antiparticle pair and a
particle/antiparticle pair can annihilate into
an energetic photon.
• Annihilation and Creation happened
continuously
=>There was an equal amount of matter and
anitmatter
The asymmetry between matter
and antimatter
15
The CKM-matrix and the γparameter
• The mixing of quarks in weak
interactions is described by the
CKM-matrix.
• The complex Vxy entries of the
matrix are the nine gw
parameters.
• The matrix can be written in a
way that only two entries are left
complex arguments. The
arguments of those two entries
are measurable.
• We want to measure one of these
entries. .
  Vudud

  Vcdcd
 i
 V tV
e
d
td


The asymmetry between matter
and antimatter
VVusus Vubub e 


VVcscs VVcbcb 
VVtsts VVtbtb 
i
16
Proposed project
• Improving the reconstruction program
• Developing the selection procedure of
the Bs->DsK events
• Developing the fitting method in order
to obtain the γ-parameter from the
selected events
The asymmetry between matter
and antimatter
17