CERN Accelerating science

Posters

Последно добавени:
2015-03-11
11:40
$\sin(2\beta)$ with $B^0 \rightarrow\!J/\!\psi K_\text{S}$ at the LHCb experiment
Reference: Poster-2015-482
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Niet, Ramon

The poster presents the recent measurement of $\sin(2\beta)$ using $B^0$ decays to the $J/\!\psi K_\text{S}$ final state. The measurement is based on a dataset corresponding to an integrated luminosity of 3.0$\,\text{fb}^{-1}$ collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV. To control penguin pollutions in the determination of $\sin(2\beta)$, $B_s^0$ decays to the same final state can be analysed. The results of the corresponding analysis are presented as well.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-11
11:32
Study of the rare $B^{0}_{s}$ and $B^{0}$ decays into the $\pi^{+}\pi^{-}\mu^{+}\mu^{-}$ final state at LHCb
Reference: Poster-2015-481
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Komarov, Ilya

A search for the rare decays B0s->pi pi mu mu and B0->pi pi mu mu is performed in a data set corresponding to an integrated luminosity of 3.0 fb-1 collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5--1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0s->pi pi mu mu and the first evidence of the decay B0->pi pi mu mu are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be Br(B0s->pi pi mu mu) = (8.6 +/- 1.5 (stat) +/- 0.7 (syst) +/- 0.7 (norm))*10^-8 and Br(B0->pi pi mu mu) = (2.11 +/- 0.51 (stat) +/- 0.15 (syst) +/- 0.16 (norm)) *10^-8, where the third uncertainty is due to the branching fraction of the decay B0->J/psi K*, used as a normalisation.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-11
11:21
Topological Trigger Developments
Reference: Poster-2015-480
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Likhomanenko, Tatiana

The main b-physics trigger algorithm used by the LHCb experiment is the so-called topological trigger. The topological trigger selects vertices which are a) detached from the primary proton-proton collision and b) compatible with coming from the decay of a b-hadron. In the LHC Run 1, this trigger utilized a custom boosted decision tree algorithm, selected an almost 100% pure sample of b-hadrons with a typical efficiency of 60-70%, and its output was used in about 60% of LHCb papers. This talk presents studies carried out to optimize the topological trigger for LHC Run 2. In particular, we have carried out a detailed comparison of various machine learning classifier algorithms, e.g., AdaBoost, MatrixNet and uBoost. The topological trigger algorithm is designed to select all "interesting" decays of b-hadrons, but cannot be trained on every such decay. Studies have therefore been performed to determine how to optimize the performance of the classification algorithm on decays not used in the training. These include cascading, ensembling and blending techniques. Furthermore, novel boosting techniques have been implemented that will help reduce systematic uncertainties in Run 2 measurements. We demonstrate that the reoptimized topological trigger is expected to significantly improve on the Run 1 performance for a wide range of b-hadron decays

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-11
09:17
Flavour Tagging with the LHCb experiment
Reference: Poster-2015-479
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Birnkraut, Alex

Measurements of flavour oscillations and time-dependent CP asymmetries in neutral B meson systems require knowledge of the b quark production flavour. This identification is performed by the Flavour Tagging.

Related links:
LHCC conference poster
Access to files

Подробен запис - Подобни записи
2015-03-06
17:15
Measurement of the semileptonic $CP$ asymmetry in $B^0 - \bar {B^0}$ mixing
Reference: Poster-2015-478
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): De Vries, Jacco

The semileptonic CP asymmetry in B0−B⎯⎯⎯0 mixing, adsl, is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, recorded by the LHCb experiment. Semileptonic B0 decays are reconstructed in the inclusive final states D−μ+ and D∗−μ+, where the D− meson decays into the K+π−π− final state, and the D∗− meson into the D⎯⎯⎯0(→K+π−)π− final state. The asymmetry between the numbers of D(∗)−μ+ and D(∗)+μ− decays is measured as a function of the decay time of the B0 mesons. The CP asymmetry is measured to be adsl=(−0.02±0.19±0.30)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of adsl to date and is consistent with the prediction from the Standard Model.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-06
17:03
$\mathcal{CP}$ violating phase $\phi_s$ and penguin pollution in $B_s^0\to J/\psi K^+K^-$ with LHCb
Reference: Poster-2015-477
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Vazquez Sierra, Carlos

CP violating phase φs appears in b → anti(c)cs transitions due to the interference between the direct decay and the decay after the Bs⁰-anti(Bs⁰) mixing. In SM, φs = -2βs + δP, where -2βs is related to CKM matrix elements and δP is the penguin phase where contributions due to penguin diagrams are taken into account, being this δP phase also the main source of theoretical uncertainty in φs. This φs phase is very sensitive to possible NP (new particles contributing to box diagrams during the mixing, several possible BSM scenarios are presented), so δP should be estimated in order to disentangle these penguin pollution contributions from possible NP contributions, φs(LHCb) = -2βs + δP + δNP. The decay Bs⁰ → J/ψ K⁺K⁻ is a golden decay for φs measurement: latest LHCb combined result also including Bs⁰ → J/ψ π⁺π⁻ measurements is φs = -0.010 ± 0.039 rad, which is in excellent agreement with SM. The penguin pollution phase δP can be estimated using B⁰ → J/ψ ρ⁰ and Bs⁰ → J/ψ anti(K*⁰) decay channels separately: measurement in B⁰ → J/ψ ρ⁰ decay is |δP| < 0.02 rad at 95% CL. Measurement in Bs⁰ → J/ψ anti(K*⁰) decay channel is still ongoing.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-06
16:51
Differential branching fraction and angular anaysis of Λb→Λμ+μ− decays
Reference: Poster-2015-476
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Pescatore, Luca

The differential branching fraction of the rare decay Λ0b → Λμ+μ− is measured as a function of q2, the square of the dimuon invariant mass. The analysis is performed using data collected by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb−1. These include evidence for signal at dimuon masses below the square of the J/ψ mass with significance above 3σ. In the q2 intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon and hadron systems are measured for the first time.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-06
16:25
Search for Exotics with LHCb
Reference: Poster-2015-475
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Muster, Bastien

A search is presented for long-lived particles with a mass between 25 and 50 GeV/c^2 and a lifetime between 1 and 200ps in a sample of proton-proton collisions at a centre-of-mass energy of \sqrt{s} = 7TeV, corresponding to an integrated luminosity of 0.62fb^{-1}, collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a Standard Model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets. No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-06
16:18
Electroweak Physics in the Forward Region
Reference: Poster-2015-474
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Sirendi, Marek

LHCb has an active electroweak physics programme with measurements of inclusive processes such as Z and W production in leptonic final states already published. The EW working group is also branching into jet physics with completed Z+jet and Z+b-jet analyses. Recent results in this field are presented.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
2015-03-06
15:25
First Observation and Measurement of the Branching Fraction for the Decay $B^0_S \rightarrow D{_S}^* K$
Reference: Poster-2015-473
Created: 2015. -1 p
Creator(s): Sestini, Lorenzo

The Bs -> Ds* K and Bs -> Ds* \pi decays are of paramount interest as they can be used, combined with Bs -> Ds K and Bd -> D* \pi, to measure the weak phase \gamma. We present the first observation of the Bs -> Ds* K decay, where Ds* are reconstructed through the decay chain Ds* -> Ds (-> K K \pi) \gamma, using an integrated luminosity of 3.0 fb^{-1} recorded by the LHCb experiment.

Related links:
LHCC conference poster
© CERN Geneva

Access to files

Подробен запис - Подобни записи
Акценти върху:
Open Days 2013 Posters (58)