the asymmetry between matter and antimatter

The Asymmetry between Matter and

Antimatter

Besma M’charekFEW, Vrije Universiteit Amsterdam

The asymmetry between matter and antimatter

2

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

3

Matterq

uark

sele

ctronNucleusneutron

proton

atom

Matter/antiMatter

The asymmetry between matter and antimatter

4

“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

5

Where is the antimatter?

The asymmetry between matter and antimatter

6

EM

EW

Where is the antimatter?

life

13.7 billion y

1st stars

1 billion y

3000K

300,000 y

H/He

300 s106 s1011 s

matter +antimatter

< 1011 sA

atom

nucleushadrons

The asymmetry between matter and antimatter

7

Charge Parity symmetry

• Parity symmetry : • Parity P reflects a system

into its mirror-image• What if your image

behaves differently than you??

• Charge symmetry:• Charge conjugation C

changes the electric charge of the particle.

• e + e - • K - K +

•Charge Parity symmetry:•Changes a particle into its antiparticle.

=>In weak interactions, parity symmetry is always violated

=>In weak interactions, charge symmetry is always violated

=>In weak interactions, CP is almost never violatedalmost

The asymmetry between matter and antimatter

8

P

P

C C

Escher on CP violation…

CP

The asymmetry between matter and antimatter

9

Weak interactions

A main difference between electromagnetic and weak interactions is in the coupling

constants ge and gubeiγ , ..• 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

photon

ge

gubeiγ

u

b

Weak interactions

Electromagnetic interactions

W+

ie

The asymmetry between matter and antimatter

10

B-mesons in the LHCb detector •B-mesons mix to:

•In the LHCb detector, we want to study weak interaction with the special B-decays:

Two quarks, one is

always a b-quarkB-

mesons

B

s s

s s

s s

s s

B D K

B D K

B D K

B D K

B B

The asymmetry between matter and antimatter

11

CERN

4.4 km

1989-2000 LEP e+e (88-209 GeV)2007-2015 LHC pp (14000 GeV)

LHCb

Atlas

Alice

CMS

The asymmetry between matter and antimatter

12

The LHCb detector

The detector

Results

Simulation and Reconstruction

The asymmetry between matter and antimatter

13

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

14

Additional slides!!!

The asymmetry between matter and antimatter

15

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

16

The CKM-matrix and the γ-parameter

• 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. .

ud us ub

cd cs cb

td ts tb

V V V

V V V

V V V

iub

it

ud us

cd cs cb

ts tbd

V e

V e

V V

V V V

V V

The asymmetry between matter and antimatter

17

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