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Yeni Kuvvetler. CMS bir genel amaçl ı proton-proton çarp ış ma deney olup birbirinden ba ğ ı ms ı z olmayan iki ana hedefi vard ı r: . a) Yeni madde türlerinin aranmas ı . b) Yeni kuvvet yasalar ı n ı n aranmas ı . . proton. 1) Bilinen parçac ı klar (elektron, müon, hafif

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slide1

YeniKuvvetler

CMS bir genel amaçlı proton-proton çarpışma deney olup birbirinden bağımsız olmayan iki ana hedefi vardır:

a) Yeni madde türlerinin aranması.

b) Yeni kuvvet yasalarının aranması.

proton

1) Bilinen parçacıklar (elektron, müon, hafif

hadronlar, foton)‏

2) Gözlemlenemeyen parçacıklar (nötrinolar, nötralinolar, …)‏

?

Ekm=14 TeV

proton

slide2

Yeni Kuvvetler

kuvvet

Graviton’

Foton

Graviton

Z bozon

Higgs’

W bozon

Bütün yeni fizik

modelleri için !

W’ bozon

Higgs

Parçacıklar

Z’ bozon

Yeni parçacıklar

slide3

Yeni Kuvvetler

eşlenik kuvvet

Fotino

En hafifi = Kara Madde

Gravitino

Zino

Higgsino’

Wino

Süpersimetrik

modeller için !

Wino’

Higgsino

Parçacıklar

Zino’

Yeni parçacıklar

slide4

Open questions

CP violation : Universe to consist largely of matter.

  • Why is charge quantized?
    • There appears to be approximate unification of the couplings at a mass scale MGUT ~ 1015 GeV.
    • Then we combine quarks and leptons into GUT multiplets - the simplest possibility being SU(5).

[dR dB dG e+e] : 3(-1/3 ) + 1 + 0 = 0

    • Since the sum of the projections of a group generator in a group multiplet is = 0 (e.g. the angular momentum sum of m), charge must be quantized in units of the electron charge.
    • In addition, we see that quarks must have 1/3 fractional charge because there are 3 colors of quarks - SU(3).

Mass hierarchy

slide5

Why the quark flavors are conserved in strong interactions, while flavors are changing in weak decays (u --> d W+ --> d e+ ne)‏

  • Why is V approximately diagonal ? Experimentally the matrix V characterizing the strength of the couplings in the weak decays of quarks, with q ~ 0.2 and A ~ 1. Why?
  • Why is b --> c so slow with respect to u --> s ?
  • Is V complex? Unitary or CP violation?
  • What is the dynamics of weak decays between generations?

All the data (BaBar and Belle) is consistent with a unitary CKM mixing matrix  3 generations with no new Physics yet indicated

slide6

supersymmetry

  • Supersymmetry relates fermions and bosons
  • The generators of this symmetry contain the Poincare generators and a spinor connecting J states to J-1/2 states.
  • Recall that in a quantum loop the fermions and bosons contribute with opposite signs (e.g. top and Higgs in the W boson mass loops).
  • Thus SUSY is very stable under radiative corrections – solves the “hierarchy problem”.
  • This is fine, but is there any “evidence” for a “SUSY – GUT”?

All particles in the SM must have a SUSY partner. None have yet been observed. Therefore, SUSY must be a broken symmetry, with SUSY masses > 100 GeV.

  • The running of coupling constants is altered by these new particles in the loops. The evidence for unification is now stronger, with MGUT = 2 x 1016 GeV and 1/GUT ~ 24.
  • Unification --> SUSY particles are in the (100 - 1000) GeV mass range
  • The prediction for sin2W at the Z mass is also altered because the evolution down from 3/8 is changed. The prediction goes from 0.206 to 0.23, significantly improving the agreement with experiment, 0.2312.
slide7

The decay of protons is slowed ( recall MGUT-4 dependence) in SUSY-GUT removing the conflict with experimental upper limits. The proton is quasi-stable because MGUT is very large.

  • The 2 mass scales, MGUT and MZ make SU(5) without SUSY difficult to keep stable under radiative (loop) corrections. If the Higgs mass is fixed at the GUT scale, then there is a quadratic divergence in running down to the Z mass scale. Thus 2 numbers of order MGUT must subtract to a number of order MZ.
  • In unbroken SUSY the SUSY partners of the SM particles are mass degenerate, and thus the loop corrections vanish, solving the “hierarchy problem”.

With SUSY breaking, the Higgs mass gets radiative corrections due to the differences of masses of the SUSY and SM partners.

  • SUSY requires that the Higgs has a mass ~ the Z mass. Radiative corrections --> MH < 130 GeV.Thus in SUSY a light Higgs is expected.
  • Therefore, SUSY solves the hierarchy problem, but only if MSUSY is < 1 TeV

MGUT = 2 x 1016 GeV and 1/GUT ~ 24

Why SUSY?

  • GUT Mass scale, unification
  • Improved Weinberg angle prediction
  • p decay rate
  • Neutrino mass (seesaw)‏
  • Mass hierarchy – Planck/EW
  • Dark matter candidate
  • String connections
slide8

SUSY

MMSM has ~ SM light h and ~ mass degenerate H,A. LSP is neutralino. Squarks and gluinos are heavy.

The SUSY cross sections for squarks and gluinos are large because they have strong couplings.

 ~ s2/(2M)2 ~ 1 pb for M = 1 TeV.

slide9

The gluino pair production cascade decays to jets + leptons + missing Et.

The gaugino pairs cascade decay to missing Et + 3 leptons which is a very clean signature

slide10

Backgrounds are QCD jet mismeasures, and Z invisible decays. SUSY signals should dominate at large values of missing transverse momentum.

Backgrounds are QCD jet mismeasures, and Z invisible decays. SUSY signals should dominate at large values of missing transverse momentum. No evidence yet.

The SUSY signals involving jets and missing ET dominate for gluinos with missing Et > 150 GeV

Study for CMS squark and gluino search

slide11

signal

Events for 10 fb-1

background

 Tevatron reach

ET(j1) > 80 GeV

ETmiss > 80 GeV

SUSY Masses at Tevatron

Events for 10 fb-1

Position of peak correlated to SUSY mass scale

signal

MSUSY

Measurement ofSUSY mass scale 20%

(mSUGRA) with 10 fb-1

Low trigger thresholds necessary to measure mass scale in overlap region with Tevatron (400 GeV)‏

Background

slide12

SUSY Cross Sections at LHC

Squarks and gluinos are most copious (strong production). Cascade decay to LSP ( )  study jets and missing energy. E.g. 600 GeV squark. Dramatic event signatures and large cross section mean we will discover SUSY quickly at the LHC, if it exists.

Squarks and gluinos are most copious (strong production). Cascade decay to LSP ( )  study jets and missing energy. E.g. 600 GeV squark. Dramatic event signatures and large cross section mean we will discover SUSY quickly at the LHC, if it exists.

slide13

SUSY – Mass Scale

Will immediately start to measure the fundamental SUSY parameters.

With 4 jets + missing energy the SUSY mass scale can be established to 20 %.

1 year at l/10th design luminosity

CMS can set limits on SUSY(SUGRA) particles such that < 2 TeV is excluded. Recall that SUSY masses must be < 1 TeV if the hierarchy problem is to be solved. CMS can also set limits on the LSP mass which span the cosmologically interesting range for dark matter.

slide14

Sparticle Cascades

Use SUSY cascades to the stable LSP to sort out the new spectroscopy.

Decay chain used is :

Then

And

Final state is

slide15

Sparticle Masses

An example of the kind of analysis done, from 1 year at 1/10th design luminosity.

Sequential

2-body decay: edge in Mll

10 fb-1

slide16

Sparticle Reconstruction

Can measure mass differences to better than 10%. The LSP is inferred from missing Et which makes the overall mass scale less well determined.

slide17

What is Jet

How many Jets?

slide20

Thrust axis

Phase space constraint

(p=0 particles do not contribute)‏

slide21

Jet Finding

Choose smallest yij

Massive jets

Massless jets

Gluon jet

Collinear gluons  3-jets events

Cleaning of Junk jets:

Transverse momenta

slide22

Sphericity

S 1 : isotropic

S  0 : Jet like

T ½ isotropic

T 1 Jet like

slide25

Main physics interest: dijets in the squark production

Squark  Jet+ MissingEnergy

Squark  Jet+ 3 leptons + ME (inc neutrino)‏

Sq  Jet+ l + ME (inc neutrino)‏

Sq  2 l + ME

Squark  Jet+ 3 leptons + ME

~uR is absent

Squark  Jet+ l + ME (inc neutrino)‏

~uR is absent

Squark  Jet+ 2 l + ME

Squark  Jet+ 3 leptons + ME

(2 more neutrino)‏

slide26

1-)‏

2-) heavier squarks

3-) gluinos lighter then squarks

slide27

background

Others signal our background

> 150 GeV

4 lepton final states

if

slide30

From Physics TDR

Signal events were generated at the test point LM1,where the NLO cross section at NLO is about 52 pb, dominated by the production of ˜q˜g, ˜g˜g and ˜q¯˜q. The gluino is the heaviest particle and decays to ˜qq.

slide31

SM entire spectrum

1 Jet events: pp --> gZ, gW, gg

pp --> 1 Jet + 0,1,2.. leptons + (missing energy)‏

slide34

3Jet events: pp --> qqg, qqbar g, ggg, ggq

pp --> 3 Jets + ( 0 missing energy)‏

pp --> 3 Jets + (missing energy)‏

slide36

for each cathegory:

Efficiency sensitivity =

A: 1 Jet + 0 Missing Energy events

1 Jet + Missing Energy events

B: Jets + 0 lepton + 0 Missing Energy events

Jets + 0 lepton + Missing Energy events

C: Jets + 1 lepton + 0 Missing Energy events

Jets + 1 lepton + Missing Energy events

D: Jets + 2 lepton + 0 Missing Energy events

Jets + 2 lepton + Missing Energy events

E: Jets + 3 lepton + 0 Missing Energy events

Jets + 3 lepton + Missing Energy events

slide37

General selection

  • Topological selection
  • Define Hemispheres, using thrust axis
  • - require 0, 1, 2, 3 leptons in each hemisphere
  • -require jets in different hemisphere (1-1; or 1-2, or 2-2,..etc)