Calibration System with Cryogenically-Cooled Loads for CMB Polarization Detectors

We present a novel system to calibrate millimeter-wave polarimeters for CMB polarization measurements. This technique is an extension of the conventional metal mirror rotation approach, however it employs cryogenically-cooled blackbody absorbers. The primary advantage of this system is that it can generate a slightly polarized signal ($\sim100$ mK) in the laboratory; this is at a similar level to that measured by ground-based CMB polarization experiments observing a $\sim$ 10 K sky. It is important to reproduce the observing condition in the laboratry for reliable characterization of polarimeters before deployment. In this paper, we present the design and principle of the system, and demonstrate its use with a coherent-type polarimeter used for an actual CMB polarization experiment. This technique can also be applied to incoherent-type polarimeters and it is very promising for the next-generation CMB polarization experiments.Comment: 7 pages, 9 figures Submitted to RS

Innovative Demodulation Scheme for Coherent Detectors in CMB Experiments

We propose an innovative demodulation scheme for coherent detectors used in cosmic microwave background polarization experiments. Removal of non-white noise, e.g., narrow-band noise, in detectors is one of the key requirements for the experiments. A combination of modulation and demodulation is used to extract polarization signals as well as to suppress such noise. Traditional demodulation, which is based on the two- point numerical differentiation, works as a first-order high pass filter for the noise. The proposed demodulation is based on the three-point numerical differentiation. It works as a second-order high pass filter. By using a real detector, we confirmed significant improvements of suppression power for the narrow-band noise. We also found improvement of the noise floor.Comment: 3 pages, 4 figure

Weak Phase gamma Using Isospin Analysis and Time Dependent Asymmetry in B_d -> K_s pi^+ pi^-

We present a method for measuring the weak phase gamma using isospin analysis of three body B decays into K pi pi channels. Differential decay widths and time dependent asymmetry in B_d -> K_s pi^+pi^- mode needs to be measured into even isospin pi pi states. The method can be used to extract gamma, as well as, the size of the electroweak penguin contributions. The technique is free from assumptions like SU(3) or neglect of any contributions to the decay amplitudes. By studying different regions of the Dalitz plot, it is possible to reduce the ambiguity in the value of gamma.Comment: 11 pages, 1 figur

Proper-time Resolution Function for Measurement of Time Evolution of B Mesons at the KEK B-Factory

The proper-time resolution function for the measurement of the time evolution of B mesons with the Belle detector at KEKB is studied in detail. The obtained resolution function is applied to the measurement of B meson lifetimes, the B0-B0bar oscillation frequency and time-dependent CP asymmetries.Comment: 25 pages, 18 figures, to be published in NIM A, replaced with revised versio

Mixing-Induced CP Violation in B -> P_1 P_2 gamma in Search of Clean New Physics Signals

We show that in a decay of the form B_d or B_s-> P_1 P_2 gamma (where P_1 and P_2 are pseudoscalar mesons), through a flavor changing dipole transition, time dependent oscillations can reveal the presence of physics beyond the Standard Model. If P_1 and P_2 are CP eigenstates (e.g. as in B_d -> K_S pi0 gamma), the oscillation is independent of the resonance structure. Thus data from resonances as well as from nonresonant decays can be included. This may significantly enhance the sensitivity to new physics of the method. If P_1 is a charged particle, and P_2 its anti-particle (e.g. as in B_d -> pi+ pi- gamma), one has the additional advantage that both the magnitude and the weak phase of any new physics contribution can be determined from a study of the angular distribution. These signals offer excellent ways to detect new physics because they are suppressed in the Standard Model. We also show that the potential contamination of these signals originating from the Standard Model annihilation diagram gives rise to photons with, to a very good approximation, the same helicity as the dominant penguin graph and thus causes no serious difficulty.Comment: 13 pages 4 figures Version 4: We have added a para (2nd para below Eqn.39, Section VII) and a new Ref. (#20

Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR

A half-wave plate (HWP) is often used as a modulator to suppress systematic error in the measurements of cosmic microwave background (CMB) polarization. A HWP can also be used to measure circular polarization (CP) through its optical leakage from CP to linear polarization. The CP of the CMB is predicted from various sources, such as interactions in the Universe and extension of the standard model. Interaction with supernova remnants of population III stars is one of the brightest CP sources. Thus, the observation of the CP of CMB is a new tool for searching for population III stars. In this paper, we demonstrate the improved measurement of the leakage coefficient using the transmission measurement of an actual HWP in the laboratory. We measured the transmittance of linearly polarized light through the HWP used in \textsc{Polarbear} in the frequency range of \SIrange{120}{160}{GHz}. We evaluate properties of the HWP by fitting the data with a physical model using the Markov Chain Monte Carlo method. We then estimate the band-averaged CP leakage coefficient using the physical model. We find that the leakage coefficient strongly depends on the spectra of CP sources. We thus calculate the maximum fractional leakage coefficient from CP to linear polarization as $0.133 \pm 0.009$ in the Rayleigh--Jeans spectrum. The nonzero value shows that \textsc{Polarbear} has sensitivity to CP. Additionally, because we use the bandpass of detectors installed in the telescope to calculate the band-averaged values, we also consider systematic effects in the experiment.Comment: 27 pages, 7 figure

Neutral B Flavor Tagging for the Measurement of Mixing-induced CP Violation at Belle

We describe a flavor tagging algorithm used in measurements of the CP violation parameter sin2phi_1 at the Belle experiment. Efficiencies and wrong tag fractions are evaluated using flavor-specific B meson decays into hadronic and semileptonic modes. We achieve a total effective efficiency of $ 28.8 +- 0.6 %.Comment: 28 pages, 9 figure