Se Search for Dark Matter produc uced in n as associat ation - - PowerPoint PPT Presentation
Se Search for Dark Matter produc uced in n as associat ation with a a Higgs bo boson at at LHC by Reham Mohamed Aly PhD student Physics Department Bari University Tutor Prof. /Nicola De Filippis Polittecnico and INFN, Bari Corso
by
Reham Mohamed Aly
PhD student Physics Department – Bari University
Tutor
Polittecnico and INFN, Bari
Corso di Dottorato XXXIII Ciclo
Particle physics is the
study of what everything is made of ?
What is the nature of
This study is called
Elementary particle Physics or sometimes High Energy Physics (HEP).
Elementary particle is a
particle not known to have substructure.
2
04/07/2012 the Higgs boson has been found !
3
4
Ø Gravity: It does not construct a theory of gravity similar to those for the
force, gravity.
Ø Unified Problem:The Standard Model does not offer a unified
description of all the fundamental forces.
Ø Why do we observe matter and almost no antimatter if we believe there
is a symmetry between the two in the universe? What happened to antimatter after Big Bang?
Ø Fermion generations: why are there exactly three generations of leptons
and quarks?
Ø Dark matter& Dark energy: No candidate in SM.
Ø Cosmology Observations indicate
that:
Ø 4% of universe is Visible Matter (SM) Ø 23% of universe is Dark Matter (DM) Ø 73% of universe is Dark Energy
Ø “The great majority our universe is unseen
& visible stars, galaxies and clusters account for 4% of the universe.”
Ø Dark matter is a hypothetical type
such as protons, neutrons and electrons.
Ø The name refers to the fact that it does not
emit or interact with electromagnetic radiation.
5
Properties:
Ø Long Lived (old) Ø Non relativistic particles (Slow) Ø No electric or color charge Ø Very Weakly Interacting with standard model particles Ø Subject to gravity
There are several candidates fulfill these requirements for Dark Matter
Hot & Dark: Ultra-relativistic velocity
Ø neutrinos
Warm & Dark: Very high velocity
Ø sterile neutrinos & gravitons.
Cold & Dark: moving slowly
Ø Weakly interacting massive particles (WIMP)
No such particle exists in the SM
6
DM SM SM DM DM DM SM SM DM SM DM SM
Experiments search for the SM products from DM annihilation. Experiments look for nuclear recoil produced when a DM particle collide with an atomic nucleus of a target. Produce DM particles by colliding SM particles at high energy. Appear as “Missing Energy”
7
Ø Dark matter search at LHC has been
performed with various Mono-X + Missing Et signatures (Where X = W, Z, jet, H or γ)
Ø Here X could be emitted directly from a
quark as ISR or as a part of new effective vertex coupling DM to SM
Ø Unlike W, Z, jets or γ, Higgs ISR is highly
suppressed -> mono-Higgs Signal could be probe directly the structure of the effective DM SM coupling.
Ø Experimental Signature : MET + 4l from
Higgs decay
8
Simplified Model
A new massive particle (Z’,S,A0) mediates DM-H interaction
arXiv:1312.2592 arXiv:1402.7074
Ø PesudoScalar A0 mediator Ø Vector Z’ mediator Ø Scalar mediator
9
Ø Signature:
Ø 4l + MET Ø Based on Standard Model H-> ZZ-> 4l analysis Ø Channels: 4e, 4µ and 2e2µ
µ + ΜΕΤ final state
Ø We will study the leptons (e, µ) reconstruction
algorithm and MET .
Ø Data : Will use 2017 data collected by CMS Ø Background
Ø Irreducible: ZH, Z→νν and H→ZZ→4l or Z→ll and H→ZZ→2l2ν (MC) Ø Reducible: - Non-resonant ZZ→4l + MET
Ø We need to study the discrimination of the background from our signal.
10
Ø Signal
Ø We need to put an upper limit on the DM mass using 2017 data plus 2016 data.
ØM x = (1 – 10 -50 – 150 – 500 - 1000)GeV ØM Z’ (10 – 100 - 200 – 1000 – 2000 - 10000) GeV ØM A0 = 300 - 800 GeV with step 100 ØM Z’ from 600 to 2500 with step 200
11
12
13
Ø In 1933, Fritz Zwicky studied the
nearest large galaxy cluster “Coma Galaxy Cluster ”.
Ø In this study he estimated how
much mass in the cluster based on the motions of galaxies in the cluster, then he compared to the estimated mass from Luminous matter.
Ø He concluded that the cluster had
about 400 times more mass than was visually observable.
Ø There should be some a lot of
‘Missing Matter- Dark matter’
vGalaxy clusters
14
Ø About 47 years later Vera Rubin
was observing the rotational curves of galaxies“orbital speeds
radial distance from the galaxy center”
Ø She measured where you go
further and further away, the velocity of dust and stars remain high.
Ø Her conclusion is to assume that
there is a halo of invisible matter (Dark Matter) surrounded the galaxy.
vRotational curves of galaxies
15
16
Ø When a massive objects (such as a
cluster of galaxies) lying between a more distant source and an observer should act as a lens to bend the light from this source. The more massive an
Ø What observed is a distortion of
background galaxies into arcs when their light passes through such a gravitational lens.
Ø By measuring the distortion => the
geometry and the mass of the cluster can be obtained, scientists have been able to map the distribution of dark matter around the galaxy cluster.
vGravitational lensing
17