2024-08-27 16:53

Status: #started Tags: [[p8_ee_ZH_ecm240]] [[zh_recoil_example]] [[physics_of_examples]] [[fcc-analyses]]

ZH Recoil Example Physics

Event Generation

Ref. [[Event Generation]]

Signal and Background

Signal

  • The main process is a production of a Higgs Boson along with a Z Boson.

![[Pasted image 20240827170959.png]]

  • Specifically, we look at the two muon final state of this reaction.

  • This process is also known as Higgsstrahlung.

  • This process is used for precise measurement of Higgs mass on the order of MeV.

  • Explain : Model-independent cross-section: sensitive to new physics H → invisible

  • Higgstrahlung is the dominant mode of Higgs production for $e^+e^- \rightarrow SOMETHING$

  • $10^6$ ZH events @ 240 GeV 5 /ab

Energy Equation

Signal Extraction: Recoil Mass Distribution $$\vec{p_{in}} = 0 = \vec{p}{recoil} + \vec{p{\mu \mu}} \ \ \ (3 \ momentum)$$

$$ p_{in} = p_{out} \ \ \ (4 \ momentum) $$

$$ (E_e, \vec{p_e}) + (E_e, \vec{-p_e}) = (E_{recoil}, \vec{p}{recoil}) + (E{\mu \mu}, \vec{p}_{\mu \mu}) $$

$$ 2E_e = E_{recoil} + E_{\mu \mu}$$ $$ \sqrt{s} = E_{recoil} + E_{\mu \mu}$$ $$ E_{recoil} = \sqrt{s} - E_{\mu \mu}$$ $$ \left( E_{recoil} \right)^2 =\left( \sqrt{s} - E_{\mu \mu}\right)^2 $$ $$ M_{recoil}^2 + \vec{p}{recoil}^2 = s + E{\mu \mu}^2 - 2\sqrt{s} E_{\mu \mu}$$ $$ M_{recoil}^2 + \vec{p}{recoil}^2 = s + m{\mu \mu}^2 + \vec{p}{\mu \mu}^2 - 2\sqrt{s} E{\mu \mu}$$ $$ M_{recoil}^2 = s + m_{\mu \mu}^2 - 2\sqrt{s} E_{\mu \mu} + \vec{p}{\mu \mu}^2 - \vec{p}{recoil}^2$$ $$ M_{recoil}^2 = s + m_{\mu \mu}^2 - 2\sqrt{s} E_{\mu \mu}$$ Signal Sample used : p8_ee_ZH_ecm240 (inclusive decays) Cross Section : 0.201868 $pb^{-1}$ (pythia 8.303)

To get a feel of what inclusive decays mean: Consider the following samples generated by Whizard-Pythia6 :

sample name

process (inclusive Higgs decays)

cross section in $pb^{-1}$

wzp6_ee_mumuH_ecm240

$e^+e^-\rightarrow ZH \rightarrow \mu^+ \mu^-H$

0.0067643

wzp6_ee_tautauH_ecm240

$e^+e^-\rightarrow ZH \rightarrow \tau^+ \tau^-H$

0.0067518

wzp6_ee_eeH_ecm240

$e^+e^-\rightarrow ZH \rightarrow e^+ e^-H$

0.0071611

wzp6_ee_nunuH_ecm240

$e^+e^-\rightarrow ZH \rightarrow \nu \bar{\nu}H$

0.046191

wzp6_ee_qqH_ecm240

$e^+e^-\rightarrow ZH \rightarrow q \bar{q}H$

0.13635

Total

Z inclusive decay

0.20322

0.20322 (whizard-pythia6) is close to 0.201868 (pythia8.303)

Major Backgrounds

  • $ZZ$

  • $WW$

  • $Z/\gamma* \rightarrow l\bar{l}$

  • $Z/\gamma* \rightarrow q\bar{q}$

  • $\gamma \gamma \rightarrow \mu\mu$

sample name

process

cross section in $pb^{-1}$

p8_ee_ZZ_ecm240

$ZZ$

1.35899

p8_ee_WW_ecm240

$WW$

16.4385

p8_ee_Zll_ecm240

$Z/\gamma* \rightarrow l\bar{l}$

13.7787

p8_ee_Zqq_ecm240

$Z/\gamma* \rightarrow q\bar{q}$

52.6539

NA

$\gamma \gamma \rightarrow \mu\mu$

NA

![[Pasted image 20240828005217.png]]

References

  1. Higgs mass and cross-section studies using ZH recoil with Z → μμ

Doubts

  • Why is it called Isolation and Acceptance criteria for the cut muon pt > 10 GeV ?

  • What is the role of a PDF? is it actually a probability density function?

  • What is a Two-sided Crystall Ball?

  • What do we use CMS Combine for?

  • What is an Asimov plot/dataset?