docs: add page for HL-LHC analysis blueprint (#2463)

_blueprints/HL_LHC_analysis.md

@@ -0,0 +1,29 @@
+---
+layout: blueprint
+visible: true
+topic: Physics analysis at the HL-LHC
+meetingurl:
+meetingdate: Spring 2025
+focus-areas:
+    - as
+    - doma
+    - ssl
+status: proposed
+location: Virtual
+documents:
+---
+
+"End-user physics analysis", starting from centrally provided files and ending with a published paper, is a field with a diverse set of approaches.
+Despite often occupying a significant fraction of physicists' time, this last step in the pipeline is generally less well understood in terms of workflow and computational cost than earlier stages.
+We propose a workshop in spring 2025 to identify a representative set of physics analyses, described in terms of workflow and computational needs.
+The workshop should result in a document summarizing these analyses, alongside an extrapolation of how we expect them to evolve at the HL-LHC.
+
+The main two questions we expect to discuss are the following:
+
+- What are the computational needs of representative end-user physics analyses today, in terms of overall workflow, services used, number of events and total volume of data to process, and computational cost per event?
+- Which scenarios should we consider to extrapolate these physics analyses’ needs toward the HL-LHC?
+
+Achieving community consensus will help move many connected areas of software R&D forward.
+The document will be an important ingredient for understanding how long physics analysis at the HL-LHC will take; ensuring that it can comfortably fit into the timescale of a PhD is crucial for the future of our field.
+It will provide more clarity about the role of analysis facilities and the kinds of services they should make available.
+It will allow for quantitative evaluation of analysis models and be a first step towards identifying what to do about analysis use cases that do not fit into the space set out by the benchmark examples.