Dark matter results from 100 live days of XENON100 data

We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time-projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows the selection of only the innermost 48 kg as the ultralow background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in the signal region with an expected background of (1.8 ± 0.6) events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic weakly interacting massive particle (WIMP) nucleon scattering cross sections above 7.0 × 10(-45) cm(2) for a WIMP mass of 50 GeV/c(2) at 90% confidence level.     

Multiplicity structure of proton and kaon diffractive dissociation in 10 and 16 GeV/c K-p interactions

A new method to calculate diffractive mass spectra has been developed. It is applied to K^-p interactions at 10 and 16 GeV/c. Cross sections and mass spectra are given for the difractive dissociation processes p→(N+iπ) and K^-p→(K+iπ) for i = 1 to 5 and also summed over all multiplicities. In addition to the diffractive peak at low mass coming from low multiplicities, a long tail extending to high masses and high multiplicities has been found. The multiplicity structure of diffraction dissociation can be understood in the context of the two-step dynamical picture of Pokorsky and Van Hove.     

Photocytotoxicity of a new Rh2(II,II) complex: increase in cytotoxicity upon irradiation similar to that of PDT agent hematoporphyrin

A new type of heteroleptic dirhodium complex cis-[Rh(2)(mu-O2CCH3)2-(bpy)(dppz)]2+ (3) was synthesized and its potential as a photodynamic therapy (PDT) agent was investigated. Although 27% hypochromicity of the absorption of 3 in the near-UV and visible regions is observed in the presence of duplex DNA, relative viscosity measurements reveal that the complex does not intercalate between the DNA bases. The DNA photocleavage with visible light by 3 proceeds via both oxygen dependent and independent mechanisms, and it is more efficient than that of related complexes. The increase in the cytotoxicity of 3 towards human skin cells is similar to that of hematoporphyrin, a key ingredient in a PDT drug currently in use. This feature makes this complex a useful candidate for further PDT studies.     

Study of proton dissociation into ΛK+ in 3-body final states at 10 and 16 GeV/c

Results are presented for p → (ΛK⁺) dissociation in the reactions K^?p → ΛK⁺K^? and and π^±p → ΛK⁺π^±at 10 and 16 GeV/c. The cross sections for the low-mass ΛK⁺ enhancement are compatible with the energy dependence σ ∝ p_lab^?0.3. The t′ spectra or the (ΛK⁺) threshold enhancement are exponential in shape. Its decay angular distribution reveals neither s-channel nor t-channel helicity conservation. The relative probabilities of the processes $\text{p}\text{→}\text{p, p}\text{→ (}\text{N}\text{π)}{}_{\mathrm{<mtext>I=</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{and p}\text{→ (Λ}\text{K}{}^{\mathrm{+}}\text{)}$ dissociation are in the ratios 100 : 10 : 0.2, independent of the nature of the incident particle.     

cis-[Rh2(mu-O2CCH3)2(CH3CN)6]2+ as a photoactivated cisplatin analog

The complex cis-[Rh2(mu-O2CCH3)2(CH3CN)6]2+ (1) exchanges the two axial CH3CN ligands for solvent molecules in water to yield cis-[Rh2(mu-O2CCH3)2(CH3CN)4(H2O)2]2+ (2). Photolysis of 2 in H2O results in the photoaquation of two equatorial acetonitrile ligands to yield [Rh2(mu-O2CCH3)2(CH3CN)2(H2O)4]2+ (3), which is able to covalently bind to free 2,2'-bipyridine (bpy) and 9-ethylguanine in solution, as well as double-stranded DNA (lambdairr >/= 455 nm). Complex 2 exhibits 20-fold lower cytotoxicity towards human skin cells than hematoporphyrin in the dark, and its toxicity increases by a factor of 34 when irradiated with visible light (400-700 nm, 30 min). This increase in cytotoxicity by 2 upon irradiation is approximately 7 times greater than that measured for hematoporphyrin. These properties make 2 a promising photo-cisplatin analog and a potential agent for photodynamic therapy. To our knowledge, 2 is the first metal-metal bonded complex to bind to DNA upon irradiation with visible light.     

DNA photocleavage by a supramolecular Ru(II)-viologen complex

A novel Ru(II) complex possessing two sequentially linked viologen units, Ru-V(1)-V(2)(6+), was synthesized and characterized. Upon excitation of the Ru(II) unit (lambda(exc) = 532 nm, fwhm approximately 10 ns), a long-lived charge-separated (CS) state is observed (tau = 1.7 micros) by transient absorption spectroscopy. Unlike Ru(bpy)(3)(2+), which cleaves DNA upon photolysis through the formation of reactive oxygen species, such as (1)O(2) and O(2)(-), the photocleavage of plasmid DNA by Ru-V(1)-V(2)(6+) is observed both in air and under N(2) atmosphere (lambda(irr) > 395 nm).     

N=82 shell quenching of the classical r-process "waiting-point" nucleus 130Cd

First beta- and gamma-spectroscopic decay studies of the N=82 r-process "waiting-point" nuclide 130Cd have been performed at CERN/ISOLDE using the highest achievable isotopic selectivity. Several nuclear-physics surprises have been discovered. The first one is the unanticipatedly high energy of 2.12 MeV for the [pi g(9/2) multiply sign in circle nu g(7/2)] 1(+) level in 130In, which is fed by the main Gamow-Teller transition. The second surprise is the rather high Q(beta) value of 8.34 MeV, which is in agreement only with recent mass models that include the phenomenon of N=82 shell quenching. Possible implications of these new results on the formation of the A approximately 130 r-process abundance peak are presented.     

Spin and lifetime of the ω− hyperon

A total of 101 ω^? decays have been found in K^?p interactions at 10 and $\text{16 GeV}\text{c}$. The decay angular distribution has been fitted under the assumptions that the ω^? has spin either $\text{1}\text{2}\text{or}\text{3}\text{2}$. It has been found that the probability of isotropy (spin$\text{1}\text{2}\text{)}$ is less than one in a thousand, whereas the probability for spin $\text{3}\text{2}$ is about 70%. Thus, we exclude the spin $\text{1}\text{2}$ assignment. The lifetime of the ω^? is found to be (1.41_?0.24^+0.15) × 10^?10s, in agreement with our earlier result based on about $\text{1}\text{5}$ of the present sample.