Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

INTRODUCTION

The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures.

METHODS

In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025.

FINDINGS

Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2-6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5-5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4-10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32-4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23-11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation.

INTERPRETATION

After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Surviving critical illness: what is next? An expert consensus statement on physical rehabilitation after hospital discharge

BACKGROUND

The study objective was to obtain consensus on physical therapy (PT) in the rehabilitation of critical illness survivors after hospital discharge. Research questions were: what are PT goals, what are recommended measurement tools, and what constitutes an optimal PT intervention for survivors of critical illness?

METHODS

A Delphi consensus study was conducted. Panelists were included based on relevant fields of expertise, years of clinical experience, and publication record. A literature review determined five themes, forming the basis for Delphi round one, which was aimed at generating ideas. Statements were drafted and ranked on a 5-point Likert scale in two additional rounds with the objective to reach consensus. Results were expressed as median and semi-interquartile range, with the consensus threshold set at ≤0.5.

RESULTS

Ten internationally established researchers and clinicians participated in this Delphi panel, with a response rate of 80 %, 100 %, and 100 % across three rounds. Consensus was reached on 88.5 % of the statements, resulting in a framework for PT after hospital discharge. Essential handover information should include information on 15 parameters. A core set of outcomes should test exercise capacity, skeletal muscle strength, function in activities of daily living, mobility, quality of life, and pain. PT interventions should include functional exercises, circuit and endurance training, strengthening exercises for limb and respiratory muscles, education on recovery, and a nutritional component. Screening tools to identify impairments in other health domains and referral to specialists are proposed.

CONCLUSIONS

A consensus-based framework for optimal PT after hospital discharge is proposed. Future research should focus on feasibility testing of this framework, developing risk stratification tools and validating core outcome measures for ICU survivors.

Comparative study of linear and curvilinear ultrasound probes to assess quadriceps rectus femoris muscle mass in healthy subjects and in patients with chronic respiratory disease

Introduction

Ultrasound measurements of rectus femoris cross-sectional area (RF_CSA) are clinically useful measurements in chronic obstructive pulmonary disease (COPD) and critically ill patients. Technical considerations as to the type of probe used, which affects image resolution, have limited widespread clinical application. We hypothesised that measurement of RF_CSA would be similar with linear and curvilinear probes.

Methods

Four studies were performed to compare the use of the curvilinear probe in measuring RF_CSA. Study 1 investigated agreement of RF_CSA measurements using linear and curvilinear probes in healthy subjects, and in patients with chronic respiratory disease. Study 2 investigated the intra-rater and inter-rater agreement using the curvilinear probe. Study 3 investigated the agreement of RF_CSA measured from whole and spliced images using the linear probe. Study 4 investigated the applicability of ultrasound in measuring RF_CSA during the acute and recovery phases of an exacerbation of COPD.

Results

Study 1 showed demonstrated no difference in the measurement of RF_CSA using the curvilinear and linear probes (308±104 mm² vs 320±117 mm², p=0.80; intraclass correlation coefficient (ICC)>0.97). Study 2 demonstrated high intra-rater and inter-rater reliability of RF_CSA measurement with ICC>0.95 for both. Study 3 showed that the spliced image from the linear probe was similar to the whole image RF_CSA (308±103.5 vs 263±147 mm², p=0.34; ICC>0.98). Study 4 confirmed the clinical acceptability of using the curvilinear probe during an exacerbation of COPD. There were relationships observed between admission RF_CSA and body mass index (r=+0.65, p=0.018), and between RF_CSA at admission and physical activity levels at 4 weeks post-hospital discharge (r=+0.75, p=0.006).

Conclusions

These studies have demonstrated that clinicians can employ whole and spliced images from the linear probe or use images from the curvilinear probe, to measure RF_CSA. This will extend the clinical applicability of ultrasound in the measurement of muscle mass in all patient groups.

Tube feeding and quality of life in children with severe neurological impairment

OBJECTIVE

To assess the quality of life (QOL) of neurologically impaired children before and after gastrostomy (G) and gastrojejunostomy (GJ) tube insertion.

DESIGN

This was a prospective longitudinal study of children with severe neurological impairment who underwent G or GJ tube insertion. At baseline, and at 6 and 12 months after tube insertion, parents rated (1) global QOL and health-related quality of life (HRQOL) using 10 cm visual analogue scales, with 10 representing maximal QOL and (2) HR-QOL using a questionnaire-based measure.

RESULTS

Fifty patients, 45 and five of whom underwent G and GJ tube insertion, respectively, were enrolled with a median age of 591 days. Forty-two had a static neurological disorder, and eight had a progressive neurological disorder. The mean weight for age z score increased significantly over time: -2.8 at baseline and -1.8 at 12 months. The mean QOL and HR-QOL scores at baseline were 5.5 and 5.6 out of 10, respectively. There was no significant change in these scores at 6 and 12 months post-tube insertion. Children with a progressive versus a static neurological disorder had a significantly lower QOL over time. Ease of medication administration as well as feeding showed a significant improvement in scores from baseline to 12 months. Parents felt that the G and GJ tube had a positive impact on their child's health at 6 months (86%) and 12 months (84%).

CONCLUSION

QOL as rated by parents did not increase following insertion of a G or GJ tube in neurologically impaired children. However, parents felt that the tube had a positive impact on their child's health, particularly with regards to feeding and administration of medications.

An exploratory study of the association between reactive attachment disorder and attachment narratives in early school-age children

OBJECTIVE

To explore attachment narratives in children diagnosed with reactive attachment disorder (RAD).

METHOD

We compared attachment narratives, as measured by the Manchester Child Attachment Story Task, in a group of 33 children with a diagnosis of RAD and 37 comparison children.

RESULTS

The relative risk (RR) for children with RAD having an insecure attachment pattern was 2.4 (1.4-4.2) but 30% were rated as securely attached. Within the RAD group, children with a clear history of maltreatment were more likely to be Insecure-Disorganised than children without a clear history of maltreatment.

CONCLUSIONS

Reactive attachment disorder is not the same as attachment insecurity, and questions remain about how attachment research informs clinical research on attachment disorders.

The reliability of a single pulse oximetry reading as a screening test for congenital heart disease in otherwise asymptomatic newborn infants

Routine pulse oximetry has been studied to detect children with otherwise undiagnosed congenital heart disease prior to nursery discharge. The reported sensitivities in asymptomatic patients have been less than expected and vary widely, bringing into question the reliability of the test. The purpose of this study was to assess whether routine pulse oximetry contributes to identifying patients with critical congenital heart disease and to determine the reliability of a single pulse oximeter reading in screening asymptomatic newborn infants. Between December 26, 2003, and December 31, 2005, three hospitals in west central Florida performed a pulse oximetry routinely on all newborns at the time of discharge. Patients diagnosed with critical congenital heart disease during the study period were identified to assess whether the pulse oximetry reading initiated their diagnosis. In one hospital, the pulse oximeter data were evaluated for reliability. Downloaded data were compared to a log compiled by the nursery personnel, first without (phase 1) and then with (phase 2) their knowledge and additional training. Results were characterized as reliable, probe placed but reading not verifiable, or no evidence of probe placement. Of the 7962 infants who received oximetry testing, there were 12 postnatal diagnoses of critical congenital heart disease. None was initially identified by routine pulse oximetry. Pulse oximetry reliability improved substantially between phase 1 and phase 2 (38 v. 60%, p < 0.0001). Optimal reliability (>95%) was obtained by a nurse with a degree of LPN or higher performing an assessment of at least 360 seconds. Routine pulse oximetry was neither reliable nor an important diagnostic tool in our cohort. Important human factors (probe placement time, oximetry training, and nursing degree) impact single determination pulse oximetry reliability. With routine surveillance and quality improvement, the reliability of this test can be increased. Future studies to determine the effectiveness of pulse oximetry screening for the diagnosis of congenital heart disease in the asymptomatic newborn population must address these factors. Until such a study demonstrates acceptable sensitivity and clinical value, universal screening should not be instituted.

Observation of the suppression of the flux of cosmic rays above 4 x 10 (19) eV

The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.

Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV.

Reliability of a single pulse oximetry reading as a screening test for congenital heart disease in otherwise asymptomatic newborn infants: the importance of human factors

BACKGROUND

The use of routine pulse oximetry to detect neonates with undiagnosed congenital heart disease before nursery discharge has been studied. The reported sensitivities with asymptomatic patients have been less than expected and vary widely, bringing into question the reliability of the test. This study aimed to assess whether routine pulse oximetry contributes to identifying patients with critical congenital heart disease, and to determine the reliability of a single pulse oximeter reading for screening asymptomatic newborn infants.

METHODS

Between December 26, 2003 and December 31, 2005, three hospitals in west central Florida performed pulse oximetry routinely on all newborns at the time of discharge. Patients who received a diagnosis of critical congenital heart disease during the study period were identified to assess whether the pulse oximetry reading initiated their diagnosis. In one hospital, the pulse oximeter data were evaluated for reliability. Downloaded data were compared to a log compiled by the nursery personnel, first without (Phase 1) and then with (Phase 2) their knowledge and additional training. The results were characterized as reliable, probe placed but reading not verifiable, or no evidence of probe placement.

RESULTS

Among the 7,962 infants who received oximetry testing, there were 12 postnatal diagnoses of critical congenital heart disease. None was initially identified by routine pulse oximetry. Pulse oximetry reliability improved substantially between Phases 1 and 2 (38% vs 60%; p < 0.0001). Optimal reliability (>95%) was obtained by a nurse with a licensed practical nurse degree or higher performing an assessment of at least 360 s.

CONCLUSION

Routine pulse oximetry was neither reliable nor an important diagnostic tool for our cohort. Important human factors (probe placement time, oximetry training, and nursing degree) have an impact on single-determination pulse oximetry reliability. With routine surveillance and quality improvement, the reliability of this test can be increased. Future studies to determine the effectiveness of pulse oximetry screening for the diagnosis of congenital heart disease in the asymptomatic newborn population must address these factors. Until such a study demonstrates acceptable sensitivity and clinical value, universal screening should not be instituted.

Overview of the use of implantable venous access devices in the management of children with inherited bleeding disorders

Frequent infusion of factor concentrates may be challenging in young boys with haemophilia, especially if their disease is complicated by inhibitors. A central venous access device (CVAD) is often placed in young patients in need of repeated infusions for prophylaxis or immune tolerance induction. Although user friendly and capable of providing reliable venous access, these devices are associated with a high complication rate over time. In the haemophilia population, major complications include CVAD-associated infections and deep venous thrombosis, which is most often silent. Established risk factors for catheter-related infection include age less than 6 years at the time of CVAD placement and use of an external CVAD when compared with a totally implantable device such as a port. Avoidance of CVAD-related infections is facilitated by strict adherence to aseptic technique. The risk of deep venous thrombosis appears related to the duration for which the catheter is in place, with the risk increasing beyond 4 years. The promotion of a strict clinic policy in which CVADs are left in place for as short a time as possible should decrease the risk of complications. In rare cases where a totally implantable CVAD cannot be placed for technical reasons, an arteriovenous fistula may provide reliable venous access. In all cases, however, venous access via peripheral veins is preferred over CVADs.

Membranous duodenal stenosis: Initial experience with balloon dilatation in four children

INTRODUCTION

We present a novel approach to the treatment of membranous duodenal stenosis (MDS). To our knowledge this is the first paper to describe balloon dilatation for this entity.

MATERIAL AND METHODS

Four children, 2 boys and 2 girls, aged between 8 and 28 days, underwent duodenal balloon dilatation. Balloon dilatation was performed under general anaesthesia using standard angiography balloons per os. Balloon diameters ranged from 6 to 14 mm.

RESULTS

All balloon dilatations were successful. None of the procedures showed procedural or post-procedural complications. None of the patients subsequently required surgical intervention. To date all children are doing well.

DISCUSSION

The initial experience with balloon dilation of MDS showed a 100% success rate, without procedural or post-procedural complications. The results obtained in this small group of patients suggest that the use of balloon dilatation in cases of MDS may be a safe technique that can be readily performed by an experienced interventional radiologist.

Risk of ventriculoperitoneal shunt infections due to gastrostomy feeding tube insertion in pediatric patients with brain tumors

OBJECTIVE

To determine the risk of ventriculoperitoneal (VP) shunt infections after percutaneous retrograde gastrostomy feeding tube (GT) placement in children with brain tumors.

PATIENTS AND METHODS

All children (age 0-18 years) with primary brain tumors diagnosed and treated at the Hospital for Sick Children, Toronto, Canada, were subjected to a retrospective analysis. Two groups were identified: the study group included children with a VP shunt and a GT; the control group included children with VP shunts only. Each study patient was matched with 2 controls to compare the rate of infections (cohort comparative study).

RESULTS

There were 1,167 children diagnosed and treated with primary brain tumors during the study period (1988-2003); 174 (15%) had a VP shunt and 23 (2%) children had both, a VP shunt and a GT. In the study group (n=17), GTs were inserted at a median time of 80 days (range 6-204 days) after VP shunts. VP shunt infection rate was 23.5% (4/17) compared to 8.8% (3/34) in the control group (OR 3.18; 95% CI 0.622-16.54, p=0.16). Three (75%) of the infection episodes in the study group presented with an ascending VP shunt infection directly related to the GT insertion or manipulation in the first 6 weeks. These GTs were inserted at 13, 47 and 49 days after VP shunt insertion.

CONCLUSION

Placement of percutaneous retrograde GTs, in the acute phase, in children with brain tumors and VP shunts may increase the risk of ascending meningitis especially if there are early GT-related complications.

Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

Search for supersymmetry with gauge-mediated breaking in diphoton events at D0

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.

Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

Small-bowel intussusception around a gastrojejunostomy tube resulting in ischemic necrosis of the intestine

Gastrojejunostomy (GJ) tube feeding has made a significant difference in the lives of children with oropharyngeal motor problems and severe gastroesophageal reflux disease. It may, however, also lead to small-bowel intussusception. Previously, these intussusceptions have been reported as intermittent, self limiting, and innocuous. We report a case of a GJ-tube-related small-bowel intussusception that resulted in ischemic necrosis of the bowel. This case suggests that close monitoring and confirmation of successful reduction is necessary in the treatment of GJ-tube-related small-bowel intussusception.

Observation and properties of the X(3872) decaying to J/psipi(+)pi(-) in pp collisions at sqrt[s]=1.96 TeV

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

Search for doubly charged higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in pp collisions at sqrt[s]=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

A precision measurement of the mass of the top quark

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Search for narrow tt resonances in pp collisions at square root of (s)=1.8 TeV

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.