B hadron lifetimes in CMS data Jhovanny Mejia , C. Duran, M. Ramirez, - - PowerPoint PPT Presentation

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B hadron lifetimes in CMS data Jhovanny Mejia , C. Duran, M. Ramirez, - - PowerPoint PPT Presentation

Sep 25, 2023 314 likes •488 views

B hadron lifetimes in CMS data Jhovanny Mejia , C. Duran, M. Ramirez, I. Heredia, E. De La Cruz-Burelo Cinvestav IPN, Physics department High Energy Physics Group 1 / 16 Introduction All work presented here is in progress We make the

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SLIDE 1

B hadron lifetimes in CMS data

Jhovanny Mejia, C. Duran, M. Ramirez, I. Heredia, E. De La Cruz-Burelo

Cinvestav IPN, Physics department

High Energy Physics Group

1 / 16

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SLIDE 2

Introduction

  • All work presented here is in progress
  • We make the lifetime measurement of differents hadrons:

Bs → J/Ψf0, Bd → J/ΨK ∗, Bd → J/ΨK 0

s , B+ u → J/ΨK +,

Λb → J/ΨΛ0 and Ξb → J/ΨΞ−

  • We can make contributions in different topics of particle

physics like heavy quark expansion (HQE) and cp violation.

  • We will show CMS is competitive in several of the lifetime

measurements.

2 / 16

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SLIDE 3

Λb → J/ΨΛ0 puzzle

τ(B+) ≥ τ(B0

d ) ≃ τ(B0 s ) > τ(Λ0 b) ≫ τ(B− C ) m µ 280 300 320 340 360 380 400 420 440 460 480

lifetime

b

Λ

PDG (2014) Λ ψ ), J/

  • 1

LHCb (2012, 1.0 fb Λ ψ ), J/

  • 1

ATLAS (2013, 4.9 fb Λ ψ ), J/

  • 1

CDF (2011, 4.3 fb Λ ψ ), J/

  • 1

CMS (2013, 5.0 fb Λ ψ ), J/

  • 1

DØ (2012, 10.4 fb

lifetime

b

Λ

The issue of the Λb lifetime is not yet solved.

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SLIDE 4

Why the lifetime in B0

s → J/ψf0(980)?

△Γ = ΓL

s − ΓH s = 2|Γs 12|cosφs

φ = φs + φ?

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SLIDE 5

Main difficulties with lifetime

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SLIDE 6

B0

s → J/ψf0(980)

p p

Ξb → J/ψΞ−

p p

Λb → J/ψΛ0

p p

B+

u → J/ψK +

p p

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SLIDE 7

Estimate of lifetime correction

  • We searched full

simulated MC for Bd → J/Ψ + K ∗ decays and divided them in two samples: with displaced vertex trigger and without displace vertex trigger

Sample with displaced triggers Sample without displaced triggers Data Data

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SLIDE 8

Displaced vertex triggers effects

  • Effects due to triggers

with displaced vertex affects more negative and low proper decay length

  • f the B hadron.
  • Green no displaced vertex

sample and Blue displaced vertex sample λ = MB LXY · PT PT · PT

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SLIDE 9

Triggers correction

Ratio of displaced vertex to no displaced vertex samples distributions.

PDL = 0.02 µm 9 / 16

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SLIDE 10

Efficiency

Due to high variations, we selected values greater than 0.02 cm. T = a + b ∗ λ a = 0.991559±0.01108 b = 0.0917707±0.147202 chi2 = 1.20528

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SLIDE 11

How the flatness depends on the lifetime?

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.2 0.4 0.6 0.8 1

Trigger efficiency on PDL

T(λ) = a + b ∗ λ

Flatness for PDL > 200 µm does not depends on the lifetime of the B hadron.

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SLIDE 12

Probability Density Functions (Models)

PDF = fs ∗ SM ∗ Sλ ∗ Sσ ∗ +(1 − fs) ∗ BM ∗ Bλ ∗ Bσ

  • fs: sfraction of signal events
  • SM: Mass signal pdf
  • Sλ : Signal proper decay length pdf (One exponential decay

convoluted with Gaussian Resolution with event per event error)

  • Sσ: Pdf for signal in PDL error distribution (Gaussian

convoluted with exponentials)

  • BM :Background mass pdf (1 order polynomial)
  • Bλ: Pdf for background in PDL (Several exponential decays

convoluted with Gaussian Resolution with event per event error)

  • Bσ:Pdf for background in PDL error distribution (Gaussian

convoluted with exponentials)

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SLIDE 13

Results Λb → J/ΨΛ0, simultaneous fit

]

2

[GeV/c lambda ψ ^(J/

lamb

Invariant Mass B 5.45 5.5 5.55 5.6 5.65 5.7 5.75 5.8 Events / ( 0.014 ) 100 200 300 400 500 600 700 ]

2

[GeV/c lambda ψ ^(J/

lamb

Invariant Mass B 5.45 5.5 5.55 5.6 5.65 5.7 5.75 5.8 Events / ( 0.014 ) 200 400 600 800 1000 1200 1400 1600

2011 data 2012 data work in progress work in progress

Figure: mass Simultaneous fit

PDL[cm] 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Events / ( 0.0064 ) 1 10

2

10 PDL[cm] 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Events / ( 0.0064 ) 1 10

2

10

work in progress work in progress

Figure: lifetime Simultaneous fit

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SLIDE 14

Results Bs → J/Ψf0, simultaneous fit

]

2

) [GeV/c f ψ (J/

s

Invariant Mass B 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 Events / ( 0.01828 ) 100 200 300 400 500 600 ]

2

) [GeV/c f ψ (J/

s

Invariant Mass B 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 Events / ( 0.01828 ) 200 400 600 800 1000 1200 1400 1600 1800 2000

2011 data 2012 data work in progress work in progress

Figure: mass Simultaneous fit

PDL[cm] 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Events / ( 0.005 ) 1 10

2

10

3

10 PDL[cm] 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Events / ( 0.0064 ) 1 10

2

10

3

10

work in progress work in progress

Figure: lifetime Simultaneous fit

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SLIDE 15

Summary

Decay channel CMS (µm) LHCb (µm) PDG (µm) Bs → J/Ψf0 501.0 ± 11.0 510.0 ± 12.0 509.0 ± 12.0 Λb → J/ΨΛ0 446.4 ± 6.9 424.2 ± 8.1 434.9 ± 3.8 Ξb → J/ψΞ− 457.0 ± 44.0 464.5 ± 30.0 467.6 ± 81.0 B+

u → J/ΨK +

491.1 ± 0.8 490.8 ± 1.2 491.1 ± 1.2 Bd → J/ΨK ∗ 452.6 ± 1.8 456.9 ± 1.8 455.4 ± 1.5 Bd → J/ΨK 0

s

452.8 ± 2.7 449.4 ± 3.9 455.4 ± 1.5

Decay Particle Antiparticle Ratio LHCb channel (µm) (µm) (µm) (µm) Λb → J/ΨΛ0 452.8 ± 9.7 439.6 ± 9.8 1.030 ± 0.032 0.940 ± 0.035 B+

u → J/ΨK +

491.1 ± 1.2 491.0 ± 1.2 1.001 ± 0.006 1.002 ± 0.004 Bd → J/ΨK ∗ 449.7 ± 2.6 455.8 ± 2.6 0.987 ± 0.008 1.000 ± 0.008

Work in progress

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SLIDE 16

!GRACIAS!

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