This is not A.polytrichoides (which has been recorded from Khumbu Himal but mostly amongst mats of Kobresia @ 5000-5500m. It is Arenaria globiflora typically found on wind-blown dwarf juniper scrublands between 4000-5000m. This species forms small compact hemispherical tufts of rigid spiny-tipped spreading leaves, 8-10mm. It has relatively large white, short-stalked flowers. A.polytrichoides has tufts of minute leaves 2-3mm with tiny stalkless white flowers. Chris Chadwell shpa.org.uk