Photon Multiplicity Detector (PMD) is a detector used in the measurement of the multiplicity and spatial distribution of

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can ...

s produced in

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

- nucleus collisions. In short form, it is denoted by PMD. It was incorporated in the

WA93 experiment WA93 experiment (''Synonym'': Light Universal Detector or LUD) was a detector experiment conducted at CERN for studying the correlations between photons and charged particles. It was an experimental program of CERN and part of the research progra ...

. The funding for research and development of the design of PMD was done by the

Department of Atomic Energy The Department of Atomic Energy (DAE) (IAST: ''Paramāṇu Ūrjā Vibhāga'') is an Indian government department with headquarters in Mumbai, Maharashtra, India. DAE was established in 1954 with Jawaharlal Nehru as its first minister and Homi ...

(DAE) and the Department of Science and Technology (DST) of the

Government of India The Government of India (ISO 15919, ISO: Bhārata Sarakāra, legally the Union Government or Union of India or the Central Government) is the national authority of the Republic of India, located in South Asia, consisting of States and union t ...

. The detector was constructed in the collaboration of

Variable Energy Cyclotron Centre Variable Energy Cyclotron Centre (VECC) is a premier research and development unit of the Department of Atomic Energy, Government of India. The VECC has three campuses located in Kolkata, India and performs research in basic and applied nuclear ...

Kolkata Kolkata, also known as Calcutta ( its official name until 2001), is the capital and largest city of the Indian state of West Bengal. It lies on the eastern bank of the Hooghly River, west of the border with Bangladesh. It is the primary ...

Institute of Physics The Institute of Physics (IOP) is a UK-based not-for-profit learned society and professional body that works to advance physics education, physics research, research and applied physics, application. It was founded in 1874 and has a worldwide ...

Bhubaneswar Bhubaneswar () is the capital and the largest city of the States and territories of India, Indian state of Odisha. It is located in the Khordha district. The suburban region, especially the old town, was historically often depicted as ''Chakra ...

and group of universities at

Chandigarh Chandigarh is a city and union territory in northern India, serving as the shared capital of the states of Punjab and Haryana. Situated near the foothills of the Shivalik range of Himalayas, it borders Haryana to the east and Punjab in the ...

Jaipur Jaipur (; , ) is the List of state and union territory capitals in India, capital and the List of cities and towns in Rajasthan, largest city of the north-western States and union territories of India, Indian state of Rajasthan. , the city had ...

and

Jammu Jammu () is a city in Indian-administered Jammu and Kashmir (union territory), Jammu and Kashmir in the disputed Kashmir region.The application of the term "administered" to the various regions of Kashmir and a mention of the Kashmir dispute ...

Description

A PMD typically consists of two main layers Veto Detector and Preshower Detector. Veto Detector layer is designed to reject charged particles.

Photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that ...

pass through a converter in Preshower Detector layer, initiating an electromagnetic shower. The detector then measures the number of cells activated by the shower, providing information about the photon's energy and position. At

ALICE experiment A Large Ion Collider Experiment (ALICE) is one of nine Particle detector, detector experiments at the Large Hadron Collider (LHC) at CERN. It is designed to study the conditions thought to have existed immediately after the Big Bang by measu ...

, PMD was used to measure the multiplicity and

pseudorapidity In experimental particle physics, pseudorapidity, \eta, is a commonly used spatial coordinate describing the angle of a particle relative to the beam axis. It is defined as :\eta \equiv -\ln\left tan\left(\frac\right)\right where \theta is the ...

density distributions of inclusive photons at forward

rapidity In special relativity, the classical concept of velocity is converted to rapidity to accommodate the limit determined by the speed of light. Velocities must be combined by Einstein's velocity-addition formula. For low speeds, rapidity and velo ...

, spanning the range η = 2.3 to 3.9. The measurement was conducted using

LHC The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008, in collaboration with over 10,000 scientists, and ...

Run 1 and 2 data by PMD in pp (

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

- proton collisions), pPb and Pbp collisions at a centre-of-mass energy of 5.02 TeV per

nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number. Until the 1960s, nucleons were thought to be ele ...

pair.

References

Indian inventions Nuclear physics {{Nuclear-tech-stub