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

RADS(K) = BR(B− → [K + π− ]DK − ) + BR(B + → [K−π + ]DK + )
BR(B− → [K−π + ]DK − ) + BR(B + → [K + π− ]DK + )
AADS(K) = BR(B− → [K + π− ]DK − ) − BR(B + → [K−π + ]DK + )
BR(B− → [K−π + ]DK − ) + BR(B + → [K + π− ]DK + )
Similar quantities for pions, RADS(π) and AADS(π), can be defined. The experimental
challenge is to suppress the combinatorial and physics backgrounds when extracting the highly
suppressed DCS signal. Using 5 fb −1 of CDF Run II data, a likelihood fit combining mass and
particle ID information is used to distinguish the signal (D 0 π and D 0 K) modes from the background
11 . Fig. 3 shows the invariant Kππ mass distributions for DCS signal modes separately
for B + and B − decays. The yields for π and K modes are 73±16 and 34±14, respectively. The
-1
CDF Run II Preliminary L = 5 fb
int
35
2
Events per 14 MeV/c
fit
σ
(data-fit)/
30
25
20
15
10
5
0
-2
-3
-4
-5
-1012345
0
+
-
B → D π+
→ [K π+
] π+
DCS
Data
Total
+
0
B → D π+
DCS
+
0
+
B → D K
DCS
+
0*
B → D π+
+ +
B → K π-π+
0 *+ -
B → D0
e νe
+ 0 0
B → D π+
, D → X
+ 0 + 0
B → D K , D → X
Combinatorial background
5.20 5.25 5.30 5.35 5.40 5.45 5.50 5.55 5.60
- + +
2
K π π mass [GeV/c ]
5.20 5.25 5.30 5.35 5.40 5.45 5.50 5.55 5.60
2
Events per 14 MeV/c
CDF Run II Preliminary L
int
35 - 0 - + - -
B → D π → [K π ] π
DCS
Data
30
Total
- 0 -
B → D π
DCS
25
- 0 -
B → D K
DCS
- 0* -
B → D π
20
- -
B → K π+
π-
0 *-
B → D e+
ν
0 e
15
- 0 0
B → D π-,
D → X
- 0 - 0
B → D K , D → X
10
Combinatorial background
5
0
-1
= 5 fb
5.20 5.25 5.30 5.35 5.40 5.45 5.50 5.55 5.60
+ - -
2
K π π mass [GeV/c ]
5.20 5.25 5.30 5.35 5.40 5.45 5.50 5.55 5.60
Figure 3: Invariant Kππ mass distributions for data and various background and signal contributions, separately
for B + and B − decays.
DCS fraction and asymmetry results for the Kaon mode are shown in Fig. 4, demonstrating good
agreement with those from BaBar and Belle. This is the first application of the ADS method at
Figure 4: The DCS fraction and asymmetry results for the Kaon mode.
a hadron machine. CDF’s new measurement of direct CP asymmetry for the DCS modes will
be used in the future to extract γ.
2.2 Time-integrated ACP in D 0 → h + h − decays
CP violation in the charm sector has been an area of great interest. Recent studies 12 have
pointed out that, similar to D 0 oscillations, NP contributions could play a role in enhancing the
size of CP violation in the charm sector. Since in SM there is negligible penguin contribution to
the charm decays, an ACP larger than ∼0.1% would be a clear indication of NP. The relevant
asymmetry is defined as
fit
σ
(data-fit)/
-2
-3
-4
-5
-1012345
ACP(h + h − ) = Γ(D0 → h + h− ) − Γ( ¯ D0 → h + h− )
Γ(D0 → h + h− ) + Γ( ¯ D0 → h + h− . (8)
)
(5)
(6)
(7)