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1.
Phys Rev Lett ; 132(7): 075001, 2024 Feb 16.
Article in English | MEDLINE | ID: mdl-38427892

ABSTRACT

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, self-modulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma-based accelerators and represent the first characterization of hosing.

2.
Nature ; 561(7723): 363-367, 2018 09.
Article in English | MEDLINE | ID: mdl-30188496

ABSTRACT

High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration1-5, in which the electrons in a plasma are excited, leading to strong electric fields (so called 'wakefields'), is one such promising acceleration technique. Experiments have shown that an intense laser pulse6-9 or electron bunch10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above-well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies5,12. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage13. Long, thin proton bunches can be used because they undergo a process called self-modulation14-16, a particle-plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN17-19 uses high-intensity proton bunches-in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules-to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage20 means that our results are an important step towards the development of future high-energy particle accelerators21,22.

3.
Phys Rev Lett ; 131(16): 161801, 2023 Oct 20.
Article in English | MEDLINE | ID: mdl-37925688

ABSTRACT

Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A^{'}, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×10^{11} electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A^{'} couplings to photons for masses m_{A^{'}}≲0.35 GeV, and to exclude scalar and Majorana dark matter with the χ-A^{'} coupling α_{D}≤0.1 for masses 0.001≲m_{χ}≲0.1 GeV and 3m_{χ}≤m_{A^{'}}.

4.
Phys Rev Lett ; 129(16): 161801, 2022 Oct 14.
Article in English | MEDLINE | ID: mdl-36306760

ABSTRACT

A search for a new Z^{'} gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×10^{11} electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z^{'}-e coupling strength, which, for the mass range 0.3≲m_{Z^{'}}≲100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.

5.
Phys Rev Lett ; 129(2): 024802, 2022 Jul 08.
Article in English | MEDLINE | ID: mdl-35867433

ABSTRACT

A long, narrow, relativistic charged particle bunch propagating in plasma is subject to the self-modulation (SM) instability. We show that SM of a proton bunch can be seeded by the wakefields driven by a preceding electron bunch. SM timing reproducibility and control are at the level of a small fraction of the modulation period. With this seeding method, we independently control the amplitude of the seed wakefields with the charge of the electron bunch and the growth rate of SM with the charge of the proton bunch. Seeding leads to larger growth of the wakefields than in the instability case.

6.
Phys Rev Lett ; 126(16): 164802, 2021 Apr 23.
Article in English | MEDLINE | ID: mdl-33961468

ABSTRACT

We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of a long proton bunch in plasma. We show experimentally that, with sufficient initial amplitude [≥(4.1±0.4) MV/m], the phase of the modulation along the bunch is reproducible from event to event, with 3%-7% (of 2π) rms variations all along the bunch. The phase is not reproducible for lower initial amplitudes. We observe the transition between these two regimes. Phase reproducibility is essential for deterministic external injection of particles to be accelerated.

7.
Phys Rev Lett ; 126(21): 211802, 2021 May 28.
Article in English | MEDLINE | ID: mdl-34114842

ABSTRACT

We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e^{-}Z→e^{-}ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of 2.84×10^{11} electrons on target. We place new bounds on the S, P, V, A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment a_{e}, |Δa_{X}|≲10^{-15}-10^{-13} for the X mass region 1 MeV≲m_{X}≲1 GeV. These results are an order of magnitude more sensitive compared to the current accuracy on a_{e} from the electron g-2 experiments and recent high-precision determination of the fine structure constant.

8.
Diabet Med ; 38(5): e14430, 2021 05.
Article in English | MEDLINE | ID: mdl-33073393

ABSTRACT

AIMS: Sustained engagement in type 1 diabetes self-management behaviours is a critical element in achieving improvements in glycated haemoglobin (HbA1c) and minimising risk of complications. Evaluations of self-management programmes, such as Dose Adjustment for Normal Eating (DAFNE), typically find that initial improvements are rarely sustained beyond 12 months. This study identified behaviours involved in sustained type 1 diabetes self-management, their influences and relationships to each other. METHODS: A mixed-methods study was conducted following the first two steps of the Behaviour Change Wheel framework. First, an expert stakeholder consultation identified behaviours involved in self-management of type 1 diabetes. Second, three evidence sources (systematic review, healthcare provider-generated 'red flags' and participant-generated 'frequently asked questions') were analysed to identify and synthesise modifiable barriers and enablers to sustained self-management. These were characterised according to the Capability-Opportunity-Motivation-Behaviour (COM-B) model. RESULTS: 150 distinct behaviours were identified and organised into three self-regulatory behavioural cycles, reflecting different temporal and situational aspects of diabetes self-management: Routine (e.g. checking blood glucose), Reactive (e.g. treating hypoglycaemia) and Reflective (e.g. reviewing blood glucose data to identify patterns). Thirty-four barriers and five enablers were identified: 10 relating to Capability, 20 to Opportunity and nine to Motivation. CONCLUSIONS: Multiple behaviours within three self-management cycles are involved in sustained type 1 diabetes self-management. There are a wide range of barriers and enablers that should be addressed to support self-management behaviours and improve clinical outcomes. The present study provides an evidence base for refining and developing type 1 diabetes self-management programmes.


Subject(s)
Diabetes Mellitus, Type 1/therapy , Motivation/physiology , Self-Management , Diabetes Mellitus, Type 1/epidemiology , Diabetes Mellitus, Type 1/psychology , Expert Testimony/statistics & numerical data , Health Behavior/physiology , Humans , Patient Advocacy/statistics & numerical data , Psychosocial Support Systems , Self-Management/methods , Self-Management/psychology , Self-Management/statistics & numerical data , Social Behavior , Systematic Reviews as Topic , United Kingdom/epidemiology
9.
Phys Rev Lett ; 125(26): 264801, 2020 Dec 31.
Article in English | MEDLINE | ID: mdl-33449727

ABSTRACT

We study experimentally the effect of linear plasma density gradients on the self-modulation of a 400 GeV proton bunch. Results show that a positive or negative gradient increases or decreases the number of microbunches and the relative charge per microbunch observed after 10 m of plasma. The measured modulation frequency also increases or decreases. With the largest positive gradient we observe two frequencies in the modulation power spectrum. Results are consistent with changes in wakefields' phase velocity due to plasma density gradients adding to the slow wakefields' phase velocity during self-modulation growth predicted by linear theory.

10.
Phys Rev Lett ; 125(8): 081801, 2020 Aug 21.
Article in English | MEDLINE | ID: mdl-32909809

ABSTRACT

We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10^{11} electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV.

11.
Diabet Med ; 37(3): 483-492, 2020 03.
Article in English | MEDLINE | ID: mdl-31797443

ABSTRACT

Over the past 25 years, there has been significant acknowledgement of the importance of assessing the impact of diabetes on quality of life. Yet, despite the development of several diabetes-specific quality of life measures, the challenges we faced in 1995 remain. There is little consensus on the definition of quality of life because of the complexity and subjectivity of the concept. General quality of life comprises several domains of life, and these are highly individualized. Assessing the impact of diabetes on these life domains adds to the complexity. While comprehensive diabetes-specific quality-of-life measures typically increase respondent burden, brief questionnaires may not capture all relevant/important domains. Today, the lack of resolution of these challenges may explain why the impact of diabetes on quality of life is not systematically assessed in research or clinical care. Few researchers report detailed rationales for assessment, there is often a mismatch between the concept of interest and the measure selected, and data are misinterpreted as assessing the impact of diabetes on quality of life when, in reality, related but distinct constructs have been assessed, such as diabetes distress, treatment satisfaction or health status. While significant efforts are being made to increase routine monitoring of psychological well-being and understand the lived experience, no guidelines currently recommend routine clinical assessment of diabetes-specific quality of life, and there is no consensus on which questionnaire(s) to use. The gaps identified in this review need urgent attention, starting with recognition that assessment of diabetes-specific quality of life is as important as biomedical markers, if we are to improve the lives of people with diabetes.


Subject(s)
Diabetes Mellitus/epidemiology , Health Status , Quality of Life , Activities of Daily Living/psychology , Diabetes Mellitus/history , Diabetes Mellitus/psychology , Diabetes Mellitus/therapy , History, 20th Century , History, 21st Century , Humans , Quality of Life/psychology , Surveys and Questionnaires
12.
Phys Rev Lett ; 122(5): 054802, 2019 Feb 08.
Article in English | MEDLINE | ID: mdl-30822008

ABSTRACT

We give direct experimental evidence for the observation of the full transverse self-modulation of a long, relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a periodic density modulation resulting from radial wakefield effects. We show that the modulation is seeded by a relativistic ionization front created using an intense laser pulse copropagating with the proton bunch. The modulation extends over the length of the proton bunch following the seed point. By varying the plasma density over one order of magnitude, we show that the modulation frequency scales with the expected dependence on the plasma density, i.e., it is equal to the plasma frequency, as expected from theory.

13.
Phys Rev Lett ; 122(5): 054801, 2019 Feb 08.
Article in English | MEDLINE | ID: mdl-30822039

ABSTRACT

We measure the effects of transverse wakefields driven by a relativistic proton bunch in plasma with densities of 2.1×10^{14} and 7.7×10^{14} electrons/cm^{3}. We show that these wakefields periodically defocus the proton bunch itself, consistently with the development of the seeded self-modulation process. We show that the defocusing increases both along the bunch and along the plasma by using time resolved and time-integrated measurements of the proton bunch transverse distribution. We evaluate the transverse wakefield amplitudes and show that they exceed their seed value (<15 MV/m) and reach over 300 MV/m. All these results confirm the development of the seeded self-modulation process, a necessary condition for external injection of low energy and acceleration of electrons to multi-GeV energy levels.

14.
Phys Rev Lett ; 123(12): 121801, 2019 Sep 20.
Article in English | MEDLINE | ID: mdl-31633975

ABSTRACT

A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

15.
Philos Trans A Math Phys Eng Sci ; 377(2151): 20180418, 2019 Aug 12.
Article in English | MEDLINE | ID: mdl-31230571

ABSTRACT

In this article, we briefly summarize the experiments performed during the first run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013-2018) was to demonstrate that 10-20 MeV electrons can be accelerated to GeV energies in a plasma wakefield driven by a highly relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

16.
Phys Rev Lett ; 120(23): 231802, 2018 Jun 08.
Article in English | MEDLINE | ID: mdl-29932721

ABSTRACT

We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε_{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23 MeV.

17.
Persoonia ; 41: 39-55, 2018 Dec.
Article in English | MEDLINE | ID: mdl-30728598

ABSTRACT

Over the past few years, symptoms akin to late blight disease have been reported on a variety of crop plants in South America. Despite the economic importance of these crops, the causal agents of the diseases belonging to the genus Phytophthora have not been completely characterized. In this study, a new Phytophthora species was described in Colombia from tree tomato (Solanum betaceum), a semi-domesticated fruit grown in northern South America. Comprehensive phylogenetic, morphological, population genetic analyses, and infection assays to characterize this new species, were conducted. All data support the description of the new species, Phytophthora betacei sp. nov. Phylogenetic analyses suggest that this new species belongs to clade 1c of the genus Phytophthora and is a close relative of the potato late blight pathogen, P. infestans. Furthermore, it appeared as the sister group of the P. andina strains collected from wild Solanaceae (clonal lineage EC-2). Analyses of morphological and physiological characters as well as host specificity showed high support for the differentiation of these species. Based on these results, a complete description of the new species is provided and the species boundaries within Phytophthora clade 1c in northern South America are discussed.

18.
Phys Rev Lett ; 118(1): 011802, 2017 Jan 06.
Article in English | MEDLINE | ID: mdl-28106454

ABSTRACT

We report on a direct search for sub-GeV dark photons (A^{'}), which might be produced in the reaction e^{-}Z→e^{-}ZA^{'} via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The dark photons would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75×10^{9} electrons on target. We set new limits on the γ-A^{'} mixing strength and exclude the invisible A^{'} with a mass ≲100 MeV as an explanation of the muon g_{µ}-2 anomaly.

19.
Diabet Med ; 33(12): 1673-1676, 2016 12.
Article in English | MEDLINE | ID: mdl-27589089

ABSTRACT

AIMS: To estimate and discuss the allocation of diabetes research funds to studies with a psychosocial focus. METHODS: Annual reports and funded-research databases from approximately the last 5 years (if available) were reviewed from the following representative funding organizations, the American Diabetes Association, the Canadian Diabetes Association, Diabetes Australia, Diabetes UK, the Dutch Diabetes Research Foundation and the European Foundation for the Study of Diabetes, in order to estimate the overall proportion of studies allocated research funding that had a psychosocial focus. RESULTS: An estimated mean of 8% of funded studies from our sample were found to have a psychosocial focus. CONCLUSIONS: The proportion of funded studies with a psychosocial focus was small, with an estimated mean ratio of 17:1 observed between funded biomedical and psychosocial studies in diabetes research. While several factors may account for this finding, the observation that 90% of funded studies are biomedical may be partly attributable to the methodological orthodoxy of applying biomedical reductionism to understand and treat disease. A more comprehensive and systemic whole-person approach in diabetes research that resembles more closely the complexity of human beings is needed and may lead to improved care for individuals living with diabetes or at risk of diabetes.


Subject(s)
Biomedical Research/economics , Diabetes Mellitus/psychology , Research Support as Topic/economics , Diabetes Mellitus/economics , Humans , Psychology/economics , Research Support as Topic/statistics & numerical data , Resource Allocation/economics , Resource Allocation/statistics & numerical data
20.
Support Care Cancer ; 24(4): 1625-31, 2016 Apr.
Article in English | MEDLINE | ID: mdl-26404859

ABSTRACT

PURPOSE: This study reports an innovative theory-driven approach for developing filmed peer support for cancer self-management. Peer support conventionally includes empathetic interaction between people with shared experiences. This unique study considers how to authentically communicate peer empathy in a one-way film narrative. METHODS: We co-created a film based on phenomenological interviews with seven men who had volunteered to support other men by sharing their experiences of coping with prostate cancer. The film contributed to successful engagement with self-management. Interpretative phenomenological analysis of the interview data was conducted to explore the components of experiential empathy that the men had communicated. RESULTS: Four themes were identified illustrating what men wanted other men to know about coping with prostate cancer: Going into the unknown, it was difficult but I got through highlighted trauma and the importance of having a determined attitude; Only you can do it illustrated the triumph of their journey and of regaining control; I haven't changed massively reflected the importance of a constant self; and Stay involved represented the overriding need to remain part of pre-cancer social environments. CONCLUSIONS: We propose a construct framework of experiential empathy for men with prostate cancer: Resilience, Regaining Control, Continuity-of-Self, and Social Connectedness. Filmed peer support that communicates these constructs will offer wide-ranging benefit to meet the needs of this group of men in both e-health and face-to-face self-management contexts. Further research could develop this theory-driven approach to filmed peer support for other cancer groups.


Subject(s)
Empathy , Peer Group , Prostatic Neoplasms/psychology , Self Care , Self-Help Groups , Adaptation, Psychological , Aged , Humans , Male , Middle Aged , Personal Narratives as Topic , Qualitative Research , Video Recording
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