Charged Charmless Bu -> hhh decays

This is a first attempt to create and keep an webpage with all information about the Bu2hhh analysis. Here can be found presentations in various LHCb meetings and conferences. Note and some important papers can also be found here.


In the recent past, the B factories have confirmed that the Cabbibo-Kobayashi-Maskawa (CKM) matrix dynamic is the main responsible for the CP violation observed so far. More precisely, any asymmetry observed in charge conjugated B decays can be interpreted as a manifestation of the CKM phases. In the two body scenario, direct CP asymmetry was established by experiments Belle and BaBar.

Although in the three body B meson decay no CP asymmetry has been established, the Belle and BaBar collaboration claim to have seen evidence of direct CP violation but they are unable to confirm this result due to lack of statistics. In this sense, the LHCb experiment has potential to confirm and establish if there is or not CP violation in three body B meson decays.

Some of the most interesting ways for LHCb to detect CP violation is though a Dalitz Plot analysis. From a Dalitz Plot, one can obtain important information about the decay like presence of strong resonances and consequently their width and angular distribution. Even more, som regions of the Dalitz Plot can reveal a constructive or destructive interference between two neighboring resonances. Hence, the comparison of Dalitz Plot surfaces of two charge conjugated B meson is one of the most sensible methods to detect CP violation.

A direct and model independent way to measure the difference between two Dalitz surfaces is the Dalitz Plot Anisotropy or the Mirandize method. This method consists in evaluate the anisotropy by taking into account the bin content of each surface. The main feature of this method is it's applicability when dealing with small statistics already in the first year of data taken.

However, to provide a quantitative measurement of the CP violation, a full Dalitz Plot analysis is needed. For instance, the CKM phase Gamma can be directly extract from the Bu -> K pi pi decay. Based on the SU(2) flavor symmetry, the Bu -> K* pi penguin parameters can be used in the B0 and B0bar joint fit to measure the tree phase, from which Gamma is obtained. The method is based on the ability to measure independently the relative amplitudes and phases for B0 and B0bar decays in a joint untagged sample.

Also, the search for highly suppressed modes like B+ -> K- pi+ pi+ and B+ -> K+ K+ pi- or some exotic decays violating the barionic number like Bu -> pi pi p can be included in the LHCb program due to high statistics expected to be produced.

All this prospect makes the Bu2hhh analysis very promising with rich results expected soon.

Some Experimental Results

Measurement of CP asymmetries in two body decays:

Evidences of CP violation in three body decays:

Dalitz Plot analysis in three body decays:

Rare decays:

Some Methods for CP Violation Detection/Measurement:

LHCb Activities

Recent Presentations on Bu -> hhh:

Bu -> hhh Internal Note

Configuration for Real Data Plots

  • All cuts and trigger lines used to produced Bu -> hhh real data plots can be found here: under the Slide hhh link.

-- AlvaroGomesDosSantosNeto - 28-May-2010

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Topic revision: r5 - 2010-06-26 - AlvaroGomesDosSantosNeto
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