A. Putze et al.: An MCMC technique to sample transport and source parameters of Galactic cosmic rays. II. Fig. 3. Best-fit ratio for model I (blue-dotted line), II (red-dashed line), and model III (black-solid line) using dataset F: IMP7-8, Voyager1&2, ACE-CRIS, HEAO-3, Spacelab, and CREAM. The curves are modulated with Φ = 250 GV (and Φ = 225 GV at low energy). The corre- sponding best-fit parameters are gathered in Table 3. slightly lower (from 0.89 to 0.86), but CREAM data un- certainty is still too important to be conclusive. The im- pact of the low-energy ACE reanalysed data points is seen when comparing III-F with III-G1: the scatter between the derived best-fit parameters is already of the order of the statistical uncertainty (see Table 2). The data taken either during the solar minimum period (G1) or the solar maxi- mum period (G2) cover a different energy range (see Fig. 4). The χ 2 min for G2 is greater, which is not surprising, given the abnormal trend followed by these data (empty circles in Fig. 4). Nevertheless, it is reassuring to see that they lead to consistent values of the transport parameters. If we now replace the HEAO-3 data with the AMS- 01 data, the impact on the fit is striking: the best-fit dif- fusion slope δ goes from 0.86 to 0.51. As discussed in Maurin et al. (2010), HEAO-3 data strongly constrain the slope towards δ ≈ 0 . 8, even if there is a systematic energy bias in the HEAO-3 data themselves. From the AMS-01 data, we see that there could be a way of reconciling the presence of a Galactic wind and reasonable values of δ . However, the large error bars in AMS-01 data, reflected by the low χ $^{2}$/d.o.f value, does not allow to draw firm conclu- sions. Data in the same energy range from PAMELA would be helpful in that respect. Moreover, high energy data from subsequent CREAM flights or from the TRACER experi- ments will be a crucial test of the diffusion slope: at TeV energies, diffusion alone is expected to shape the observed spectra, so that the ambiguity with the effect of convection or reacceleration is lifted (Castellina & Donato 2005). For completeness, we briefly comment on the similarities and differences between the results found here and in Paper I. To follow the organisation of the previous sec- tions, the comparison with the LBM is discussed for differ- ent classes of models (I, II, and III), and then for different datasets (A, B, and C). We note that the best-fit values presented below differ slightly for those given in Paper I, as an updated set of production cross-section is used. We recall that in the LBM (see Paper I), the free pa- rameters are the normalisation of the escape length λ$_{0}$ , δ , a cut-off rigidity R$_{0}$ , and a pseudo-Alfv´enic speed V $_{a}$. The latter is linked to a true speed by means of V$_{a}$ = V a × ( hL ) 1 / $^{2}$, i.e., V$_{a}$ = 0 . 4 1 / 2 V a for h = 0 . 1 kpc and L = 4 kpc. The diffusion coefficient at 1 GV is related to the escape length by means of K$_{0}$ ≈ 0 . 5 c × ¯ µL/λ$_{0}$ , where we use µ = 2 hn ¯ m = 1 . 34 × 10 − 3 g cm − $^{2}$, leading The data are shown in Fig. 4. Thanks to the high level of modulation for the 2001-2003 ACE data, the IS (demod- ulated) B/C ratio covers nicely the gap between HEAO- 3 and lower energy data. HEAO-3 and AMS-01 data also show consistency across their whole energy range . The best-fit model parameters for these data are shown in Table 4. The low-energy data play an important part in the fitting procedure: δ decreases by 0.1 when going from III-A to III-C, and the diffusion normalisation is decreased. When the CREAM data at higher energy are taken into ac- count (III-F), the best-fit diffusion slope δ again becomes 7 4.3. Comparison of trends for the DM and for the LBM Fig. 4. B/C data used in this section. Shown are the IS data (rescaled from TOA data using E IS k = E TOA k + Φ, see Paper I). For several experiments, in addition to the error bars in the ratio, we display the energy interval from which the central energy point is obtained. Table 4. Best-fit model parameters based on different B/C datasets. Model K best 0 × 10 2 δ best V best c V best a χ $^{2}$/d.o.f Data (kpc $^{2}$Myr $^{$_{−}$1}$) (km s $^{$_{−}$1}$) (km s $^{$_{−}$1}$) III-A 2.51 1.00 21.7 35.4 2.11 III-C 0.43 0.89 18.9 36.7 1.72 III-F 0.48 0.86 18.8 38.0 1.47 III-G1 0.53 0.84 18.0 37.4 1.80 III-G2 0.46 0.85 20.0 39.6 2.73 III-G1/2 0.53 0.83 19.0 39.1 2.94 III-H 1.85 0.51 18.1 54.1 0.25 Ek/n (GeV/n) -1 10 1 10 2 10 3 10 B/C ratio 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 | | =225 MV =250 MV =250 MV) IMP7-8 ( =200 MV) Spacelab-2 ( =250 MV) HEAO-3 ( =225 MV) Voyager1&2 ( =225 MV) ACE 97-98 ( =425 MV) CREAM ( /dof=11.2) min 2 Model I-F ( /dof=4.68) min 2 Model II-F ( /dof=1.47) min 2 Model III-F ( Ek/n (GeV/n) 1 10 2 10 B/C ratio 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 IS IMP7-8 (Garcia-Munoz et al. 1987) Voyager1&2 (Lukasiak 1999) ACE 97-98 (De nolfo et al. 2006) ACE 97-98 (George et al. 2009) ACE 01-03 (George et al. 2009) AMS-01 (Tomassetti et al. 2009) HEAO-3 (Engelmann et al. 1990) Spacelab-2 (Swordy et al. 1990) CREAM 04 (Ahn et al. 2008) – G1: as F, but with new ACE 1997-1998 data, 31 data points; – G2: as F, but with new ACE 2001-2003 data only, 31 data points; – G1/2: using both 1997-1998 and 2001-2003 ACE data, 37 data points; – H: as F, but HEAO-3 replaced by AMS-01 data, 27 data points.