Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

カン サイボウガン ニ タイスル ラジオハ ショウシャク リョウホウ ゴ ノ キョクショ サイハツ ヨソク インシ ニ ツイテノ ケントウ

肝細胞癌(HCC)に対する経皮的ラジオ波焼灼療法(RFA)後の局所再発因子について検討した.対象はHCC43例,45結節,平均年齢66.5±10.3歳,男性29例,女性14例であった.病因はHBV4例,HCV38例,原因不明1例.平均腫瘍径は2.2±0.7(1.0～4.5)cm,単発例が14例,多発例が29例であった.RFA単独治療群が20結節,他の内科的治療併用群が25結節.治療後にダイナミックCTを施行し,遺残なしと判定された結節について多変量解析にて局所再発因子を検討した.局所再発率の算出にはKaplan-Meier法を用いた.効果判定のCTは43例45結節中,腎不全合併例2例2結節を除く43結節に施行し,39結節(90.7%)が遺残なしと判定された.遺残が疑われた4例は,他疾患合併などの理由から追加治療は施行されなかった.遺残なし群(39例)の1年,2年,3年の局所再発率は,20.5%,27.5%,27.5%,これらのうち単発例14結節の局所再発率は1,2,3年ともに16.3%であった.39例における多変量解析の結果,年齢,性差,腫瘍径,臨床病期,併用療法の有無,治療前のAFP値はいずれも統計学的には局所再発に寄与せず,治療前のPIVKA-II値のみに統計学的な有意差を認め,HCCの局所再発への関与が示唆された.We have investigated the factors underlying the local recurrence of hepatocellular carcinoma (HCC) after percutaneous radiofrequency ablation (RFA). Forty-five nodules in 43 HCC patients, consisting of 29 men and 14 women with a mean age of 66.5±10.3 years, were studied. The cause of HCC was HBV in 4 patients, HCV in 40, and cryptogenic in 1. The mean tumor diameter was 2.2±0.7cm (1.0-4.5). Fourteen patients had single HCC nodule and 29 patients had multiple HCC nodules. Two treatment groups were set up: the RFA alone group of 20 nodules and the combined group of 25 nodules that were treated with another medical therapy together with RFA. After treatment, all nodules were evaluated by dynamic CT, and those judged as having "no residual tumor" were examined for local recurrence factors using multivariate analysis. The recurrence rate was calculated by the Kaplan-Meier method. CT for outcome assessment, carried out in 43 nodules in 41 patients excluding 2 patients (2 nodules) with renal failure revealed that 39 nodules (90.7%) had no residual tumor. The 4 nodules, suspected of having a residual tumor, were not additionally treated because of the presence of complications. The local recurrence rates at 1, 2 and 3 years after treatment in the "no residual tumor" group (n=39) were 20.5, 27.5 and 27.5%, respectively. The multivariate analysis revealed that neither of age, sex, tumor diameter, clinical stage, combined therapy, nor AFP value statistically contributed to local recurrence. Only PIVKA-II value was a statistically independent factor for local recurrence of HCC. In conclusion, detailed examination with dynamic CT appears necessary for the assessment of RFA treatment for HCC. PIVKA-II value is likely the most important factor to predict the local recurrence of HCC after RFA