Electric dipole rovibrational transitions in HD molecule

The rovibrational electric dipole transitions in the ground electronic state of the HD molecule are studied. A simple, yet rigorous formula is derived for the transition rates in terms of the electric dipole moment function $D(R)$, which is calculated in a wide range of $R$. Our numerical results for transition rates are in moderate agreement with experiments and previous calculations, but are at least an order of magnitude more accurate.Comment: 7 pages, 1 figur

The single t-quark productions via the flavor-changing processes in the topcolor-assisted technicolor model at the hadron colliders

In the framework of topcolor-assisted technicolor(TC2) model, there exist tree-level flavor-changing (FC) couplings which can result in the loop-level FC coupling $tcg$. Such $tcg$ coupling can contribute significant clues at the forthcoming Large Hadron Collider (LHC) experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving $tcg$ coupling at the Tevatron and LHC: $pp(p\bar{p})\to t\bar{q}(q=u,d,s),tg$. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling $tcg$. On the other hand, these processes can also provide some valuable information of the coupling $tcg$ with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model.Comment: 15 pages, 10 figure

Flavour changing effects on e^+ e^- -> H b \bar{s}, H \bar{b} s in the MSSM

Flavour changing effects originating from the exchange of scalar particles in the processes e^+ e^- -> H b \bar{s}, H \bar{b} s, with H = h^0, H^0, A^0, are investigated in the Minimal Supersymmetric Standard Model with non-minimal flavour violation at the one-loop level. The dominating SUSY-QCD contributions with squark--gluino loops are calculated and discussed. We consider the SUSY scenario with non-minimal flavour mixing in the down-type squark-mass matrix. The flavour-changing cross sections are derived, and we discuss the dependence on the MSSM parameters and the strength of flavour mixing. The values for the cross section can reach 10^{-4} pb for the production of the heavy Higgs boson H^0 or A^0, and only 10^{-7} pb for the light Higgs boson h^0. Non-decoupling behaviour occurs for both h^0, H^0 production in the case of a common heavy SUSY mass scale.Comment: LaTeX, 20 pages, 11 figures. Discussion and references added. Published version in Eur.Phys.J.

The CARMENES search for exoplanets around M dwarfs - Photospheric parameters of target stars from high-resolution spectroscopy

The new CARMENES instrument comprises two high-resolution and high-stability spectrographs that are used to search for habitable planets around M dwarfs in the visible and near-infrared regime via the Doppler technique. Characterising our target sample is important for constraining the physical properties of any planetary systems that are detected. The aim of this paper is to determine the fundamental stellar parameters of the CARMENES M-dwarf target sample from high-resolution spectra observed with CARMENES. We also include several M-dwarf spectra observed with other high-resolution spectrographs, that is CAFE, FEROS, and HRS, for completeness. We used a {chi}^2 method to derive the stellar parameters effective temperature T_eff, surface gravity log g, and metallicity [Fe/H] of the target stars by fitting the most recent version of the PHOENIX-ACES models to high-resolution spectroscopic data. These stellar atmosphere models incorporate a new equation of state to describe spectral features of low-temperature stellar atmospheres. Since T_eff, log g, and [Fe/H] show degeneracies, the surface gravity is determined independently using stellar evolutionary models. We derive the stellar parameters for a total of 300 stars. The fits achieve very good agreement between the PHOENIX models and observed spectra. We estimate that our method provides parameters with uncertainties of {sigma} T_eff = 51 K, {sigma} log g = 0.07, and {sigma} [Fe/H] = 0.16, and show that atmosphere models for low-mass stars have significantly improved in the last years. Our work also provides an independent test of the new PHOENIX-ACES models, and a comparison for other methods using low-resolution spectra. In particular, our effective temperatures agree well with literature values, while metallicities determined with our method exhibit a larger spread when compared to literature results

Non-Born-Oppenheimer calculations of the lowest vibrational energy of HD including relativistic corrections

In this work we report variational calculations of the two lowest vibrational states of the HD molecule within the framework that does not assume the Born-Oppenheimer BO approximation. The nonrelativistic energies of the states were corrected for the relativistic effects of the order of 2 where = 1 c , calculated as expectation values of the operators representing these effects with the nonrelativistic non-BO wave functions. The non-BO wave functions were expanded in terms of the one-center explicitly correlated Gaussian functions multiplied by even powers of the internuclear distance. The v=0→1 transition energy obtained in the calculations is compared with the previous calculations, as well as with the transition frequency obtained from the experimental spectra. The comparison shows the need to include corrections higher than second order in to further improve the agreement between the theory and the experimen

GATA2 deficiency and MDS/AML: experimental strategies for disease modelling and future therapeutic prospects

The importance of predisposition to leukaemia in clinical practice is being increasingly recognized. This is emphasized by the establishment of a novel WHO disease category in 2016 called 'myeloid neoplasms with germline predisposition'. A major syndrome within this group is GATA2 deficiency, a heterogeneous immunodeficiency syndrome with a very high lifetime risk to develop myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML). GATA2 deficiency has been identified as the most common hereditary cause of MDS in adolescents with monosomy 7. Allogenic haematopoietic stem cell transplantation is the only curative option; however, chances of survival decrease with progression of immunodeficiency and MDS evolution. Penetrance and expressivity within families carrying GATA2 mutations is often variable, suggesting that co-operating extrinsic events are required to trigger the disease. Predictive tools are lacking, and intrafamilial heterogeneity is poorly understood; hence there is a clear unmet medical need. On behalf of the ERAPerMed GATA2 HuMo consortium, in this review we describe the genetic, clinical, and biological aspects of familial GATA2-related MDS, highlighting the importance of developing robust disease preclinical models to improve early detection and clinical decision-making of GATA2 carriers

HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud

We present results from a deep imaging search for companions around the young bona-fide and candidate brown dwarfs Cha Ha 1 to 12 in the Cha I dark cloud, performed with HST WFPC2 (R, I, Ha), VLT FORS1 (VRI), and NTT SofI (JHK). We find 16 faint companion candidates around five primaries with separations between 1.5" and 7" and magnitudes in R & I from 19 to 25 mag, i.e. up to 8 mag fainter than the primaries. While most of these companion candidates are probably unrelated background objects, there is one promising candidate, namely 1.5" SW off the M6-dwarf Cha Ha 5. This candidate is 3.8 to 4.7 mag fainter than the primary and its colors are consistent with an early- to mid-L spectral type. Assuming the same distance (140 pc) and absorption (0.47 mag in I) as towards the primary, the companion candidate has log (L(bol)/L(odot) = -3.0 +- 0.3. At the age of the primary (1 to 5 Myrs), the faint object would have a mass of 3 to 15 Jupiter masses according to Burrows et al. (1997) and Chabrier & Baraffe (2000) models. The probability for this companion candidate to be an unrelated fore- or background object is smaller than 0.7%, its colors are marginally consistent with a strongly reddened background K giant. One other companion candidate has infrared colors consistent with an early T-dwarf. In addition, we present indications for Cha Ha 2 being a close (0.2") binary with both components very close to the sub-stellar limit. Our detection limits are such that we should have detected all companions above 1 Jup with separations above 2" (320 AU) and all above 5 Jup at 0.35" (50 AU).Comment: A&A 384, 999-1011. appeared 2002, A&A 384, 999-101

CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series

Aims. The main goal of this work is to measure rotation periods of the M-type dwarf stars being observed by the CARMENES exoplanet survey to help distinguish radial-velocity signals produced by magnetic activity from those produced by exoplanets. Rotation periods are also fundamental for a detailed study of the relation between activity and rotation in late-type stars. Methods. We look for significant periodic signals in 622 photometric time series of 337 bright, nearby M dwarfs obtained by long-time baseline, automated surveys (MEarth, ASAS, SuperWASP, NSVS, Catalina, ASAS-SN, K2, and HATNet) and for 20 stars which we obtained with four 0.2-0.8 m telescopes at high geographical latitudes. Results. We present 142 rotation periods (73 new) from 0.12 d to 133 d and ten long-term activity cycles (six new) from 3.0 a to 11.5 a. We compare our determinations with those in the existing literature; we investigate the distribution of P rot in the CARMENES input catalogue,the amplitude of photometric variability, and their relation to vsin i and pEW(Halfa); and we identify three very active stars with new rotation periods between 0.34 d and 23.6 d.Comment: 34 pages, 43 figures, 2 appendix table

A Search for Very Low-mass Stars and Brown Dwarfs in the Young sigma Orionis Cluster

We present a CCD-based photometric survey covering 870 sq. arcmin in a young stellar cluster around the young multiple star sigma Orionis. Our survey limiting R, I, and Z magnitudes are 23.2, 21.8, and 21.0, respectively. From our colour-magnitude diagrams, we have selected 49 faint objects, which smoothly extrapolate the photometric sequence defined by more massive known members. Adopting the currently accepted age interval of 2-10 Myr for the Orion 1b association and considering recent evolutionary models, our objects may span a mass range from 0.1 down to 0.02 Msun, well within the substellar regime. Follow-up low-resolution optical spectroscopy (635-920 nm) for eight of our candidates (I=16-19.5) shows that they have spectral types M6-M8.5 which are consistent with the expectations for true members. Compared with their Pleiades counterparts of similar types, Halpha emission is generally stronger, while NaI and KI absorption lines appear weaker, as expected for lower surface gravities and younger ages. Additionally, TiO bands and in particular VO bands appear clearly enhanced in our candidate with the latest spectral type, SOri 45 (M8.5, I=19.5), compared to objects of similar types in older clusters and the field. We have estimated the mass of this candidate at only 0.020-0.040 Msun, hence it is one of the least massive brown dwarfs yet discovered. We also discuss in this paper the potential role of deuterium as a tracer of both substellar nature and age in very young clusters.Comment: Accepted for publication in ApJ Main Journal. 32 pages of text and tables + 9 pages of figures. Figures 3a and 3b (gif format) provided separatel

Higgs Boson Flavor-Changing Neutral Decays into Bottom Quarks in Supersymmetry

We analyze the maximum branching ratios for the Flavor Changing Neutral Current (FCNC) decays of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) into bottom quarks, h -> b\bar{s} (h=h^0,H^0,A^0). We consistently correlate these decays with the radiative B-meson decays (b-> s\gamma). A full-fledged combined numerical analysis is performed of these high-energy and low-energy FCNC decay modes in the MSSM parameter space. Our calculation shows that the available data on B(b->s \gamma) severely restricts the allowed values of B(h->b\bar{s}). While the latter could reach a few percent level in fine-tuned scenarios, the requirement of naturalness reduces these FCNC rates into the modest range B(h->b\bar{s}) ~ 10^{-4}-10^{-3}. We find that the bulk of the MSSM contribution to B(h->b\bar{s}) could originate from the strong supersymmetric sector. The maximum value of the FCNC rates obtained in this paper disagree significantly with recent (over-)estimates existing in the literature. Our results are still encouraging because they show that the FCNC modes h->b\bar{s} can be competitive with other Higgs boson signatures and could play a helpful complementary role to identify the supersymmetric Higgs bosons, particularly the lightest CP-even state in the critical LHC mass region m_{h^0} ~= 90-130 GeV.Comment: LaTeX, 19 pages, 4 tables, 7 figures. Clarifications and discussions added, references added. Slight changes in Figs2b,6b and 7b. Version accepted in JHE