Recent Heavy Flavour resultsfrom ATLAS
Adam Barton,
On behalf of ATLAS experiment2Outline
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●Introduction
J/ψ and ψ(2S) production at high pT at 13 TeV [ATLAS-CONF-2019-047]
J/ψ production associated with W ± [JHEP 01 (2020) 095]
B±c / B± production cross-section [Phys. Rev. D 104 (2021) 012010]
Pentaquark search in Λ0b → J/ψpK- [ATLAS-CONF-2019-048]
CP-Violation in B0s →J/ψ (µ+ µ-) Κ + K - [Eur. Phys. J. C 81 (2021) 342]
Study of the B+c→J/ψD+s and B+c→J/ψD∗+s decays in pp collisions at √s=13 TeV
with the ATLAS detector [ATLAS-CONF-2021-046]

Combination of the ATLAS, CMS and LHCb results on the B 0s→μ+μ−decays [ATLAS-CONF-2020-049]

3Introduction
ATLAS detects huge amount of B
hadrons● Triggering is a challenge asluminosity increases, most of Bphysics data selected by low-pT
dimuon triggers:● Resolution in m(µµ) : ~50 MeV at
J/ψ mass, ~150 MeV at Y(nS)
masses ~10 µm impact parameterresolution● Time resolution ~60 fs after
installation of IBL in Run 2 (30%improvement w.r.t. Run 1)●

4J/ψ and ψ(2S) production at high pT
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Heavy quarkonia provide insight into QCD near theboundary of perturbative and non-perturbative regimes
Inclusive cross section measurements are important forrefining quarkonia production models
Previous ATLAS measurements used low-threshold di-muon
triggers, limiting pT range to ~ 100 GeV → use single muon
trigger with high threshold (50 GeV)
We perform unbinned ML fit to mass and pseudo-proper
decay time τ = mµµ Lxy /(pT c), in bins of y and pT.
The double differential J/ψ and ψ(2S) cross-sections forprompt and non-prompt production is measured
pT range, GeVy range

J/ψ

60<p T <360|y|<2ψ(2S)

60<p T <140|y|<25FONLL = (Fixed Order + Next-to-Leading Logarithms)

J/ψ and ψ(2S) production at high pT[ATLAS-CONF-2019-047]

comparison to FONLL prediction*
good agreement at low pTat high pT higher cross-sections are predicted*FONLL Heavy Quark Production Matteo Cacciari,

http://www.lpthe.jussieu.fr/~cacciari/fonll/fonllform.html, accessed: 2019-09-036FONLL = (Fixed Order + Next-to-Leading Logarithms)

J/ψ and ψ(2S) production at high pTcomparison to FONLL prediction*
good agreement though somewhat higher crosssections are predicted

7J/ψ and ψ(2S) production at high pTPrompt J/ψ cross-section at 13TeV
fit CMS and ATLAS results with~(b+pT)-ngood agreement in the overlap
region8J/ψ and ψ(2S) production at high pT
non-prompt production fractions:

We simply see a plateau at 70% which
was hinted at with previousmeasurements[ATLAS-CONF-2015-030]

9J/ψ production associated with W±
For understanding charmonium production mechanism in hadronic collisions● The relative contribution of Color Singlet (CS) and Color Octet (CO)● contributions from Single (SPS) and Double Parton Scattering (DPS)● can be probed using Δφ distribution between J/ψ and W± - DPS should be flat, SPS
peaks at ~π.
● The prompt-J/ψ signal is extracted from fit to J/ψ mass andpseudo-proper decay time
● Δφ measurement indicates presence of SPS● in case of DPS, probability of producing J/ψ by second scatter:
PJ/ψ|W± = σJ/ψ/σeff● σeff is unknown → two choices from previous ATLAS
measurements:●––●

σeff = 6.3 ± 1.6stat ± 1.0syst mb from prompt J/ψ pair production
σeff = 15 ± 3stat +5-3 syst mb from W± + 2jets

We see both values consistent with data at low Δφ10J/ψ production associated with W±
We show the differential inclusive cross-section in 6 pT bins in the range: 8.5 < pT <150
GeV
We compare to two theoretical predictions●●––differ in σeff values used for estimation of DPS
SPS contribution modelled by CO model for bothcomparison suggests
smaller σeff, but both
values don’t describe
pT dependence●CS model notincluded●

[arXiv:1912.02672, submitted to PRD]

11B±c / B± production cross-section●A unique probe for heavy quark dynamics–●

use similar decay mode for B±c and B±

fiducial volume: pT >13 GeV, |y|<2.3

double differential measurement in 2 bins of y and pT● The production ratio in fiducial region (horizontal line):●–(0.34 ± 0.04 stat ± +0.06-0.02 syst ± 0.01 lifetime )%–Complements LHCb and CMS
no evident rapidity dependence
B±c cross-section decreases faster with pT than B± cross-section––

12Pentaquark search in Λ0b → J/ψpK●

4 structures observed in J/ψp mass spectrum
by LHCb.
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interpreted as pentaquark states Pc(4312)+, Pc(4380)+, Pc(4440)+and Pc(4457)+.

ATLAS search uses 4.9 fb-1 (7 TeV) and 20.9 fb-1
(8 TeV) data.
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no PID → consider all Hb → J/ψh1h2 (h1,2 = p, K, π) candidates–

modelling these contributions with analytical matrix elements
suppressing background from Λ*, K*, f, φ → m(Kπ) > 1.55 GeV
performing sequence of iterative fits in Λ0b signal region, B0(J/ψπK) and B0s (J/ψKK) control regions and in full range of
selected dataset––

signal region: (5.59, 5.65) GeV

13Pentaquark search in Λ0b → J/ψpKfit with 2 pentaquark hypothesis
with spin parity of 3/2- (light) and5/2+ (heavy)

fit with 4 pentaquark
hypothesis: masses, widths
and relative yields of narrowstates fixed to LHCb values

fit without pentaquarks

χ2/n.d.f = 69.2/37

χ2/n.d.f = 37.1/39

χ2/n.d.f = 37.1/42

Conclusions●hypotheses with 2 and 4
pentaquarks consistentwith data●hypothesis without
pentaquarks cannot beexcluded

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CP-Violation in B0s →J/ψ𝜙→ μ+μ-Κ+KThe CP-violating phase 𝜙s is sensitive to New Physics processes● In SM, 𝜙 is related to the CKM matrix elements:s●–Estimated precisely as −0.03696 rad with small uncertainty.

other B0s-B0s mixing quantities: width difference between B0s
mass eigenstates ΔΓs = ΓsH-ΓsL , average decay width Γs = (ΓsH+ΓsL)/2.
● tag whether B meson contains b or b quark at time of production
using opposite side tagging (by computing weighted sum ofcharge of tracks in cone ΔR around direction of either μ, e or btagged jet)
● Final state is admixture of CP-even(L=0,2) and CP-odd(L=1) statesdistinguished through time-dependent angular analysis● 80.5 fb-1 (13 TeV) partial Run 2 data (2015-2017)●–unbinned maximum likelihood (LH) fit to extract signal and S-waveparameters

15CP-Violation in B0s →J/ψ𝜙→ μ+μ-Κ+Kfit returned two well-separated solutions for strong phases ofCP-even and CP-odd final state configurations– Main parameters are identical in both solutions●𝜙s and ΔΓs results consistent with updated SM●~ 3σ tension in Γs with current world average [PDG2020]●
A full run-2 paper is in progress●

Eur. Phys. J. C 81 (2021) 342

16ATLAS-CONF-2021-046

New: Study of the B+c → J/ψ Ds(*)+
Decays B+c → J/ψ D*+s can occur through b decaywith c as spectator, or through annihilation
diagram.
● The analysis seeks a more precise measurementof the branching fractions and polarization using
full Run-2 data.
● Dataset 1: candidates in the events collected by
the standard dimuon or three-muon triggers
without requirements on additional ID track.
● Dataset 2: candidates collected only by thededicated B0s →J/ψ φ triggers but excluding theones used in dataset 1.
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New: Study of the B+c → J/ψ Ds(*)+: Result

Measurements are consistentwith LHCb.
● The precision of thismeasurement exceeds that of all
previous studies.
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ATLAS-CONF-2020-049

Combination of the ATLAS, CMS and LHCb results on
the B0s→μ+μ− decays
A combination of results on the rare
B0s→μ+μ− and B0→μ+μ− decays fromthe ATLAS, CMS, and LHCb
experiments using data collected at theLarge Hadron Collider between 2011
and 2016

Result consistent with SM with 2.1σ19SummaryATLAS has a rich B-Physics program● The statistical precision of many analyses can still be improved(data available)● More papers coming● ATLAS B-physics team is well prepared for Run3●

20Backups

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J/ψ and ψ(2S) production at high pTPromptNon-prompt[x1, x10 and x100 scaling applied to different rapidity ranges for visual clarity]22

J/ψ and ψ(2S) production at high pTPromptNon-prompt[x1, x10 and x100 scaling applied to different rapidity ranges for visual clarity]