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Файл:Совр эксперимент на ускорителях (4 сем, мага) / Lecture-2_MEPhI_SHiP_15_02_2024
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Modern accelerator
physics
Lecture 2
A new hidden sector beam dump type
experiment at CERN - SHiP
Alexander Malinin
MEPhI, February 15, 2024
SHiP physics case
- Search for NP at the intensity frontier;
- Superior opportunity at the SPS beam dump facility for MNP < M
- Brief description of the facility including the SHIP detector
- Portals of the light NP (assuming correctness of the SM);
- Vector portal eFmnB
- Higgs portal (
mc + lc
mn
2
)HH
+
- Neutrino portal YHTNL
- Axion portal (a/F)GmnG
- Explore τ-neutrino sector (last undetected particle of the SM
mn
, (d
a/F)
m
ygmg5y
~
ν
τ
D
).
February 15, 2024 Modern accelerator physics, Lecture 2
2
2
SHiP experiment lay-out
The setup consists of a high-density
proton target, followed by a hadron
stopper and an active muon shield,
which s w e e p s a way t h e muo n s
produced in the beam dump in order
to reduce the initial flux by six orders
o f m a g n i t u d e i n t h e d e t e c t o r
acceptance
Muon shield
Decay volume
HS spectrometer
SND Neutrino detector
The SHiP detector c onsist s of t wo
complementary parts, the scattering
and neutrino detector (SND) and the
hidden sector (HS) decay spectrometer.
The SND wi ll search f or ligh t da rk
Target
February 15, 2024 3Modern accelerator physics, Lecture 2
matter (LDM) scattering and perform
neut ri n o p h ysics .I t a l so p r o vid e s
normalisation of the yield for the hidden
particle search.
SHiP backgroung muon fluxes
Conical Decay volume to accomodate for the active magnetic shield fluxes:
February 15, 2024 Modern accelerator physics, Lecture 2 4
Decay volume vessel structure
Liquid scintillator
February 15, 2024 Modern accelerator physics, Lecture 2 5
Particles in the Standard Model
Weak EM Strong
Quarks
Charged leptons
Neutral leptons
February 15, 2024 Modern accelerator physics, Lecture 2 6
+ + +
+ + –
+ – –
Particle charges in SM
February 15, 2024 Modern accelerator physics, Lecture 2 7
Neutrino helicity and mass
The direction of the spinning is defined by the right hand rule: when holding the body with the right hand
with the fingers following the spinning the thumb points in the direction of the spinning. The right figure
shows a body moving to the right (with momentum p represented by the green arrow) and spinning in the
same direction of its movement: it has right-handed helicity. The figure on the left shows a body also
moving to the right (green arrow) but with the spinning in the opposit direction: it has left-handed helicity.
If the neutrinos are massless (we know they are not) the helicity and chirality are equal. However a
massive neutrino moves below the speed of light and we can move faster than the particle and invert the
helicity. Since for neutrinos it is equivalent to CP transformation - we will get an antineutrino! But neutrino
and antineutrino is not the same particle, we can distinguish them by interaction! → The Lorentz
covariance will be violated!
February 15, 2024 Modern accelerator physics, Lecture 2 8
νMSM extention of SM
The Neutrino Minimal Standard Model (or νMSM) is an extension of the Standard Model with three righthanded (or sterile) neutrinos. It aims to address within one consistent framework several problems
beyond the Standard Model:
Neutrino oscillations;
Baryon asymmetry of the Universe;
The existence of dark matter.
February 15, 2024 Modern accelerator physics, Lecture 2 9
Dirac and Majorana particles
Dirac equation:
Majorana equation:
Solutions to the Majorana equation can be interpreted as electrically neutral particles
that are their own anti-particle. Ths may solve the Lorentz covariance problem in
case either the neutrino mass eigenstates (in the neutrino oscillation model) are
Majorana particles or the Dirac massless neutrino are mixed with massive Majorana
particles in a seesaw mechanism or the νMSM model.
February 15, 2024 Modern accelerator physics, Lecture 2 10
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