2011 QCD and High Energy Interactions - Rencontres de Moriond ...

5 D mesons
High cross-sections of D mesons production together with clean signatures help studying one of
the first hard-QCD processes at the LHC. ATLAS has measured 5 differential cross-sections as a
function of transverse momentum and pseudorapidity for D ∗± and D ± production (see Fig. 4).
±
d σ /dp (D* ) [ µ b/GeV]
T
2
10
10
1
-1
10
ATLAS Preliminary s = 7 TeV
Data 2010
POWHEG-PYTHIA
POWHEG-HERWIG
MC@NLO
-1
Lint
= 1.1 nb
5 10 15 20 25 30 35 40
±
p (D* ) [GeV]
T
±
d σ /d| η (D* )| [ µ b]
300
250
200
150
100
50
ATLAS Preliminary s = 7 TeV
Data 2010
-1
Lint
= 1.1 nb
POWHEG-PYTHIA
POWHEG-HERWIG
MC@NLO
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
±
| η (D* )|
Figure 4: Differential cross-section for D ∗± mesons as a function of pT (left) and η (right) compared to the NLO
QCD calculations of POWHEG-PYTHIA, POWHEG-HERWIG and MC@NLO
6 B Meson Studies
Studying open b production provides another useful tool for understanding reconstruction and
flavour tagging algorithms, but serves also as a prerequisite for further studies of CP violation
and rare b hadron decays. There are many new results of ATLAS namely concerning Bd and Bs
meson observation and lifetime measurement 6 , but their description goes beyond the extent of
this paper.
7 Summary and Future Plans
The firstyear of ATLAS data-taking has brought many exciting results also in the flavour sector.
Future plans include precise B meson characterisation in several decay channels (Bd → J/ψK ∗0 ,
Bs → J/ψφ, Bc → J/ψπ) and searches for the New Physics in the Bs → µ + µ − rare decays.
References
1. ATLAS Collaboration, The ATLAS Experiment at the CERN Large Hadron Collider,
JINST 3 S08003 (2008)
2. ATLAS Collaboration, Measurement of the differential cross-sections of inclusive,
prompt and non-prompt J/ψ production in proton-proton collisions at √ s = 7 TeV,
arXiv:1104.3038v1 [hep-ex], accepted by Nuclear Physics B
3. ATLAS Collaboration, Determination of the muon reconstruction efficiency in ATLAS at
the Z resonance in proton-proton collisions at √ s = 7 TeV, ATLAS-CONF-2011-008, Feb
2011, CERN, Geneva.
4. ATLAS Collaboration, A measurement of the ATLAS muon reconstruction and trigger
efficiency using J/ψ decays, ATLAS-CONF-2011-021, Mar 2011, CERN, Geneva.
5. ATLAS Collaboration, Measurement of D (∗) meson production cross-sections in pp collisions
at √ s = 7 TeV with the ATLAS detector, ATLAS-CONF-2011-017, Mar 2011,
CERN, Geneva.
6. ATLAS Collaboration, Observation of the B0 d and B0 s mesons in the decays (B0 d → J/ψK0
→ J/ψΦ in ATLAS, ATLAS-CONF-2011-050, Apr 2011, CERN, Geneva.
and B 0 s